Auto merge of #142390 - cjgillot:mir-liveness, r=davidtwco

Perform unused assignment and unused variables lints on MIR.

Rebase of https://github.com/rust-lang/rust/pull/101500

Fixes https://github.com/rust-lang/rust/issues/51003.

The first commit moves detection of uninhabited types from the current liveness pass to MIR building.

In order to keep the same level of diagnostics, I had to instrument MIR a little more:
- keep for which original local a guard local is created;
- store in the `VarBindingForm` the list of introducer places and whether this was a shorthand pattern.

I am not very proud of the handling of self-assignments. The proposed scheme is in two parts: first detect probable self-assignments, by pattern matching on MIR, and second treat them specially during dataflow analysis. I welcome ideas.

Please review carefully the changes in tests. There are many small changes to behaviour, and I'm not sure all of them are desirable.

compiler/rustc_borrowck/src/diagnostics/move_errors.rs

@@ -139,9 +139,7 @@ fn append_to_grouped_errors(
             // whether or not the right-hand side is a place expression
             if let LocalInfo::User(BindingForm::Var(VarBindingForm {
                 opt_match_place: Some((opt_match_place, match_span)),
-                binding_mode: _,
-                opt_ty_info: _,
-                pat_span: _,
+                ..
             })) = *local_decl.local_info()
             {
                 let stmt_source_info = self.body.source_info(location);

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -335,8 +335,7 @@ pub(crate) fn report_mutability_error(
                         LocalInfo::User(BindingForm::Var(mir::VarBindingForm {
                             binding_mode: BindingMode(ByRef::No, Mutability::Not),
                             opt_ty_info: Some(sp),
-                            opt_match_place: _,
-                            pat_span: _,
+                            ..
                         })) => {
                             if suggest {
                                 err.span_note(sp, "the binding is already a mutable borrow");
@@ -750,6 +749,7 @@ fn construct_mut_suggestion_for_local_binding_patterns(
                 opt_ty_info: _,
                 opt_match_place: _,
                 pat_span,
+                introductions: _,
             })) => pat_span,
             _ => local_decl.source_info.span,
         };

compiler/rustc_interface/src/passes.rs

@@ -1095,6 +1095,7 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
                 tcx.ensure_ok().check_transmutes(def_id);
             }
             tcx.ensure_ok().has_ffi_unwind_calls(def_id);
+            tcx.ensure_ok().check_liveness(def_id);
 
             // If we need to codegen, ensure that we emit all errors from
             // `mir_drops_elaborated_and_const_checked` now, to avoid discovering

compiler/rustc_middle/src/mir/mod.rs

@@ -882,6 +882,9 @@ pub struct VarBindingForm<'tcx> {
     pub opt_match_place: Option<(Option<Place<'tcx>>, Span)>,
     /// The span of the pattern in which this variable was bound.
     pub pat_span: Span,
+    /// A binding can be introduced multiple times, with or patterns:
+    /// `Foo::A { x } | Foo::B { z: x }`. This stores information for each of those introductions.
+    pub introductions: Vec<VarBindingIntroduction>,
 }
 
 #[derive(Clone, Debug, TyEncodable, TyDecodable)]
@@ -891,7 +894,15 @@ pub enum BindingForm<'tcx> {
     /// Binding for a `self`/`&self`/`&mut self` binding where the type is implicit.
     ImplicitSelf(ImplicitSelfKind),
     /// Reference used in a guard expression to ensure immutability.
-    RefForGuard,
+    RefForGuard(Local),
+}
+
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
+pub struct VarBindingIntroduction {
+    /// Where this additional introduction happened.
+    pub span: Span,
+    /// Is that introduction a shorthand struct pattern, i.e. `Foo { x }`.
+    pub is_shorthand: bool,
 }
 
 mod binding_form_impl {
@@ -906,7 +917,7 @@ fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHas
             match self {
                 Var(binding) => binding.hash_stable(hcx, hasher),
                 ImplicitSelf(kind) => kind.hash_stable(hcx, hasher),
-                RefForGuard => (),
+                RefForGuard(local) => local.hash_stable(hcx, hasher),
             }
         }
     }
@@ -1092,12 +1103,8 @@ pub fn can_be_made_mutable(&self) -> bool {
         matches!(
             self.local_info(),
             LocalInfo::User(
-                BindingForm::Var(VarBindingForm {
-                    binding_mode: BindingMode(ByRef::No, _),
-                    opt_ty_info: _,
-                    opt_match_place: _,
-                    pat_span: _,
-                }) | BindingForm::ImplicitSelf(ImplicitSelfKind::Imm),
+                BindingForm::Var(VarBindingForm { binding_mode: BindingMode(ByRef::No, _), .. })
+                    | BindingForm::ImplicitSelf(ImplicitSelfKind::Imm),
             )
         )
     }
@@ -1109,12 +1116,8 @@ pub fn is_nonref_binding(&self) -> bool {
         matches!(
             self.local_info(),
             LocalInfo::User(
-                BindingForm::Var(VarBindingForm {
-                    binding_mode: BindingMode(ByRef::No, _),
-                    opt_ty_info: _,
-                    opt_match_place: _,
-                    pat_span: _,
-                }) | BindingForm::ImplicitSelf(_),
+                BindingForm::Var(VarBindingForm { binding_mode: BindingMode(ByRef::No, _), .. })
+                    | BindingForm::ImplicitSelf(_),
             )
         )
     }
@@ -1130,7 +1133,7 @@ pub fn is_user_variable(&self) -> bool {
     /// expression that is used to access said variable for the guard of the
     /// match arm.
     pub fn is_ref_for_guard(&self) -> bool {
-        matches!(self.local_info(), LocalInfo::User(BindingForm::RefForGuard))
+        matches!(self.local_info(), LocalInfo::User(BindingForm::RefForGuard(_)))
     }
 
     /// Returns `Some` if this is a reference to a static item that is used to

compiler/rustc_middle/src/mir/statement.rs

@@ -259,7 +259,7 @@ pub fn projection_ty_core<V, T>(
 impl<V, T> ProjectionElem<V, T> {
     /// Returns `true` if the target of this projection may refer to a different region of memory
     /// than the base.
-    fn is_indirect(&self) -> bool {
+    pub fn is_indirect(&self) -> bool {
         match self {
             Self::Deref => true,
 

compiler/rustc_middle/src/query/mod.rs

@@ -1191,8 +1191,10 @@
         desc { |tcx| "checking privacy in {}", describe_as_module(key.to_local_def_id(), tcx) }
     }
 
-    query check_liveness(key: LocalDefId) {
-        desc { |tcx| "checking liveness of variables in `{}`", tcx.def_path_str(key) }
+    query check_liveness(key: LocalDefId) -> &'tcx rustc_index::bit_set::DenseBitSet<abi::FieldIdx> {
+        arena_cache
+        desc { |tcx| "checking liveness of variables in `{}`", tcx.def_path_str(key.to_def_id()) }
+        cache_on_disk_if(tcx) { tcx.is_typeck_child(key.to_def_id()) }
     }
 
     /// Return the live symbols in the crate for dead code check.

compiler/rustc_middle/src/thir.rs

@@ -798,6 +798,8 @@ pub enum PatKind<'tcx> {
         /// (The same binding can occur multiple times in different branches of
         /// an or-pattern, but only one of them will be primary.)
         is_primary: bool,
+        /// Is this binding a shorthand struct pattern, i.e. `Foo { a }`?
+        is_shorthand: bool,
     },
 
     /// `Foo(...)` or `Foo{...}` or `Foo`, where `Foo` is a variant name from an ADT with

compiler/rustc_middle/src/ty/closure.rs

@@ -327,6 +327,11 @@ pub fn place_to_string_for_capture<'tcx>(tcx: TyCtxt<'tcx>, place: &HirPlace<'tc
                     )
                 }
             },
+            HirProjectionKind::UnwrapUnsafeBinder => {
+                curr_string = format!("unwrap_binder!({curr_string})");
+            }
+            // Just change the type to the hidden type, so we can actually project.
+            HirProjectionKind::OpaqueCast => {}
             proj => bug!("{:?} unexpected because it isn't captured", proj),
         }
     }

compiler/rustc_mir_build/messages.ftl

@@ -372,6 +372,11 @@ mir_build_union_field_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
 mir_build_union_pattern = cannot use unions in constant patterns
     .label = can't use a `union` here
 
+mir_build_unreachable_due_to_uninhabited = unreachable {$descr}
+    .label = unreachable {$descr}
+    .label_orig = any code following this expression is unreachable
+    .note = this expression has type `{$ty}`, which is uninhabited
+
 mir_build_unreachable_making_this_unreachable = collectively making this unreachable
 
 mir_build_unreachable_making_this_unreachable_n_more = ...and {$covered_by_many_n_more_count} other patterns collectively make this unreachable

compiler/rustc_mir_build/src/builder/block.rs

@@ -286,6 +286,7 @@ fn ast_block_stmts(
                                 block,
                                 node,
                                 span,
+                                false,
                                 OutsideGuard,
                                 ScheduleDrops::Yes,
                             );

compiler/rustc_mir_build/src/builder/expr/into.rs

@@ -390,18 +390,7 @@ fn is_supported_loop_match_type(ty: Ty<'_>) -> bool {
                         args,
                         unwind: UnwindAction::Continue,
                         destination,
-                        // The presence or absence of a return edge affects control-flow sensitive
-                        // MIR checks and ultimately whether code is accepted or not. We can only
-                        // omit the return edge if a return type is visibly uninhabited to a module
-                        // that makes the call.
-                        target: expr
-                            .ty
-                            .is_inhabited_from(
-                                this.tcx,
-                                this.parent_module,
-                                this.infcx.typing_env(this.param_env),
-                            )
-                            .then_some(success),
+                        target: Some(success),
                         call_source: if from_hir_call {
                             CallSource::Normal
                         } else {

compiler/rustc_mir_build/src/builder/matches/match_pair.rs

@@ -170,7 +170,7 @@ pub(super) fn for_pattern(
                 None
             }
 
-            PatKind::Binding { mode, var, ref subpattern, .. } => {
+            PatKind::Binding { mode, var, is_shorthand, ref subpattern, .. } => {
                 // In order to please the borrow checker, when lowering a pattern
                 // like `x @ subpat` we must establish any bindings in `subpat`
                 // before establishing the binding for `x`.
@@ -209,6 +209,7 @@ pub(super) fn for_pattern(
                         source,
                         var_id: var,
                         binding_mode: mode,
+                        is_shorthand,
                     }));
                 }
 

compiler/rustc_mir_build/src/builder/matches/mod.rs

@@ -579,6 +579,7 @@ pub(super) fn expr_into_pattern(
                     block,
                     var,
                     irrefutable_pat.span,
+                    false,
                     OutsideGuard,
                     ScheduleDrops::Yes,
                 );
@@ -608,6 +609,7 @@ pub(super) fn expr_into_pattern(
                     block,
                     var,
                     irrefutable_pat.span,
+                    false,
                     OutsideGuard,
                     ScheduleDrops::Yes,
                 );
@@ -739,6 +741,8 @@ pub(crate) fn declare_bindings(
             pattern,
             &ProjectedUserTypesNode::None,
             &mut |this, name, mode, var, span, ty, user_tys| {
+                let saved_scope = this.source_scope;
+                this.set_correct_source_scope_for_arg(var.0, saved_scope, span);
                 let vis_scope = *visibility_scope
                     .get_or_insert_with(|| this.new_source_scope(scope_span, LintLevel::Inherited));
                 let source_info = SourceInfo { span, scope: this.source_scope };
@@ -756,6 +760,7 @@ pub(crate) fn declare_bindings(
                     opt_match_place.map(|(x, y)| (x.cloned(), y)),
                     pattern.span,
                 );
+                this.source_scope = saved_scope;
             },
         );
         if let Some(guard_expr) = guard {
@@ -799,6 +804,7 @@ pub(crate) fn storage_live_binding(
         block: BasicBlock,
         var: LocalVarId,
         span: Span,
+        is_shorthand: bool,
         for_guard: ForGuard,
         schedule_drop: ScheduleDrops,
     ) -> Place<'tcx> {
@@ -812,6 +818,10 @@ pub(crate) fn storage_live_binding(
         {
             self.schedule_drop(span, region_scope, local_id, DropKind::Storage);
         }
+        let local_info = self.local_decls[local_id].local_info.as_mut().unwrap_crate_local();
+        if let LocalInfo::User(BindingForm::Var(var_info)) = &mut **local_info {
+            var_info.introductions.push(VarBindingIntroduction { span, is_shorthand });
+        }
         Place::from(local_id)
     }
 
@@ -1217,6 +1227,7 @@ struct Binding<'tcx> {
     source: Place<'tcx>,
     var_id: LocalVarId,
     binding_mode: BindingMode,
+    is_shorthand: bool,
 }
 
 /// Indicates that the type of `source` must be a subtype of the
@@ -2725,6 +2736,7 @@ fn bind_matched_candidate_for_guard<'b>(
                 block,
                 binding.var_id,
                 binding.span,
+                binding.is_shorthand,
                 RefWithinGuard,
                 ScheduleDrops::Yes,
             );
@@ -2742,6 +2754,7 @@ fn bind_matched_candidate_for_guard<'b>(
                         block,
                         binding.var_id,
                         binding.span,
+                        binding.is_shorthand,
                         OutsideGuard,
                         ScheduleDrops::Yes,
                     );
@@ -2775,6 +2788,7 @@ fn bind_matched_candidate_for_arm_body<'b>(
                 block,
                 binding.var_id,
                 binding.span,
+                binding.is_shorthand,
                 OutsideGuard,
                 schedule_drops,
             );
@@ -2827,6 +2841,7 @@ fn declare_binding(
                     opt_ty_info: None,
                     opt_match_place,
                     pat_span,
+                    introductions: Vec::new(),
                 },
             )))),
         };
@@ -2849,7 +2864,7 @@ fn declare_binding(
                 user_ty: None,
                 source_info,
                 local_info: ClearCrossCrate::Set(Box::new(LocalInfo::User(
-                    BindingForm::RefForGuard,
+                    BindingForm::RefForGuard(for_arm_body),
                 ))),
             });
             if self.should_emit_debug_info_for_binding(name, var_id) {

compiler/rustc_mir_build/src/builder/mod.rs

@@ -24,10 +24,12 @@
 use rustc_middle::thir::{self, ExprId, LintLevel, LocalVarId, Param, ParamId, PatKind, Thir};
 use rustc_middle::ty::{self, ScalarInt, Ty, TyCtxt, TypeVisitableExt, TypingMode};
 use rustc_middle::{bug, span_bug};
+use rustc_session::lint;
 use rustc_span::{Span, Symbol, sym};
 
 use crate::builder::expr::as_place::PlaceBuilder;
 use crate::builder::scope::DropKind;
+use crate::errors;
 
 pub(crate) fn closure_saved_names_of_captured_variables<'tcx>(
     tcx: TyCtxt<'tcx>,
@@ -67,11 +69,6 @@ pub fn build_mir<'tcx>(tcx: TyCtxt<'tcx>, def: LocalDefId) -> Body<'tcx> {
                 }
             };
 
-            // Checking liveness after building the THIR ensures there were no typeck errors.
-            //
-            // maybe move the check to a MIR pass?
-            tcx.ensure_ok().check_liveness(def);
-
             // Don't steal here, instead steal in unsafeck. This is so that
             // pattern inline constants can be evaluated as part of building the
             // THIR of the parent function without a cycle.
@@ -531,6 +528,7 @@ fn construct_fn<'tcx>(
         return_block.unit()
     });
 
+    builder.lint_and_remove_uninhabited();
     let mut body = builder.finish();
 
     body.spread_arg = if abi == ExternAbi::RustCall {
@@ -588,6 +586,7 @@ fn construct_const<'a, 'tcx>(
 
     builder.build_drop_trees();
 
+    builder.lint_and_remove_uninhabited();
     builder.finish()
 }
 
@@ -806,6 +805,78 @@ fn dump_for_debugging(&self) {
         writer.write_mir_fn(&body, &mut std::io::stdout()).unwrap();
     }
 
+    fn lint_and_remove_uninhabited(&mut self) {
+        let mut lints = vec![];
+
+        for bbdata in self.cfg.basic_blocks.iter_mut() {
+            let term = bbdata.terminator_mut();
+            let TerminatorKind::Call { ref mut target, destination, .. } = term.kind else {
+                continue;
+            };
+            let Some(target_bb) = *target else { continue };
+
+            let ty = destination.ty(&self.local_decls, self.tcx).ty;
+            let ty_is_inhabited = ty.is_inhabited_from(
+                self.tcx,
+                self.parent_module,
+                self.infcx.typing_env(self.param_env),
+            );
+
+            if !ty_is_inhabited {
+                // Unreachable code warnings are already emitted during type checking.
+                // However, during type checking, full type information is being
+                // calculated but not yet available, so the check for diverging
+                // expressions due to uninhabited result types is pretty crude and
+                // only checks whether ty.is_never(). Here, we have full type
+                // information available and can issue warnings for less obviously
+                // uninhabited types (e.g. empty enums). The check above is used so
+                // that we do not emit the same warning twice if the uninhabited type
+                // is indeed `!`.
+                if !ty.is_never() {
+                    lints.push((target_bb, ty, term.source_info.span));
+                }
+
+                // The presence or absence of a return edge affects control-flow sensitive
+                // MIR checks and ultimately whether code is accepted or not. We can only
+                // omit the return edge if a return type is visibly uninhabited to a module
+                // that makes the call.
+                *target = None;
+            }
+        }
+
+        for (target_bb, orig_ty, orig_span) in lints {
+            if orig_span.in_external_macro(self.tcx.sess.source_map()) {
+                continue;
+            }
+            let target_bb = &self.cfg.basic_blocks[target_bb];
+            let (target_loc, descr) = target_bb
+                .statements
+                .iter()
+                .find_map(|stmt| match stmt.kind {
+                    StatementKind::StorageLive(_) | StatementKind::StorageDead(_) => None,
+                    StatementKind::FakeRead(..) => Some((stmt.source_info, "definition")),
+                    _ => Some((stmt.source_info, "expression")),
+                })
+                .unwrap_or_else(|| (target_bb.terminator().source_info, "expression"));
+            let lint_root = self.source_scopes[target_loc.scope]
+                .local_data
+                .as_ref()
+                .unwrap_crate_local()
+                .lint_root;
+            self.tcx.emit_node_span_lint(
+                lint::builtin::UNREACHABLE_CODE,
+                lint_root,
+                target_loc.span,
+                errors::UnreachableDueToUninhabited {
+                    expr: target_loc.span,
+                    orig: orig_span,
+                    descr,
+                    ty: orig_ty,
+                },
+            );
+        }
+    }
+
     fn finish(self) -> Body<'tcx> {
         let mut body = Body::new(
             MirSource::item(self.def_id.to_def_id()),
@@ -978,6 +1049,10 @@ fn args_and_body(
                                 opt_ty_info: param.ty_span,
                                 opt_match_place: Some((None, span)),
                                 pat_span: span,
+                                introductions: vec![VarBindingIntroduction {
+                                    span,
+                                    is_shorthand: false,
+                                }],
                             }))
                         };
                     self.var_indices.insert(var, LocalsForNode::One(local));

compiler/rustc_mir_build/src/errors.rs

@@ -720,6 +720,18 @@ pub(crate) struct WantedConstant {
     pub(crate) const_path: String,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(mir_build_unreachable_due_to_uninhabited)]
+pub(crate) struct UnreachableDueToUninhabited<'desc, 'tcx> {
+    pub descr: &'desc str,
+    #[label]
+    pub expr: Span,
+    #[label(mir_build_label_orig)]
+    #[note]
+    pub orig: Span,
+    pub ty: Ty<'tcx>,
+}
+
 #[derive(Diagnostic)]
 #[diag(mir_build_const_pattern_depends_on_generic_parameter, code = E0158)]
 pub(crate) struct ConstPatternDependsOnGenericParameter {

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -369,6 +369,7 @@ fn lower_pattern_unadjusted(&mut self, pat: &'tcx hir::Pat<'tcx>) -> Box<Pat<'tc
                     ty: var_ty,
                     subpattern: self.lower_opt_pattern(sub),
                     is_primary: id == pat.hir_id,
+                    is_shorthand: false,
                 }
             }
 
@@ -386,9 +387,13 @@ fn lower_pattern_unadjusted(&mut self, pat: &'tcx hir::Pat<'tcx>) -> Box<Pat<'tc
                 let res = self.typeck_results.qpath_res(qpath, pat.hir_id);
                 let subpatterns = fields
                     .iter()
-                    .map(|field| FieldPat {
-                        field: self.typeck_results.field_index(field.hir_id),
-                        pattern: *self.lower_pattern(field.pat),
+                    .map(|field| {
+                        let mut pattern = *self.lower_pattern(field.pat);
+                        if let PatKind::Binding { ref mut is_shorthand, .. } = pattern.kind {
+                            *is_shorthand = field.is_shorthand;
+                        }
+                        let field = self.typeck_results.field_index(field.hir_id);
+                        FieldPat { field, pattern }
                     })
                     .collect();
 

compiler/rustc_mir_build/src/thir/print.rs

@@ -705,13 +705,14 @@ fn print_pat_kind(&mut self, pat_kind: &PatKind<'tcx>, depth_lvl: usize) {
                 self.print_pat(subpattern, depth_lvl + 3);
                 print_indented!(self, "}", depth_lvl + 1);
             }
-            PatKind::Binding { name, mode, var, ty, subpattern, is_primary } => {
+            PatKind::Binding { name, mode, var, ty, subpattern, is_primary, is_shorthand } => {
                 print_indented!(self, "Binding {", depth_lvl + 1);
                 print_indented!(self, format!("name: {:?}", name), depth_lvl + 2);
                 print_indented!(self, format!("mode: {:?}", mode), depth_lvl + 2);
                 print_indented!(self, format!("var: {:?}", var), depth_lvl + 2);
                 print_indented!(self, format!("ty: {:?}", ty), depth_lvl + 2);
                 print_indented!(self, format!("is_primary: {:?}", is_primary), depth_lvl + 2);
+                print_indented!(self, format!("is_shorthand: {:?}", is_shorthand), depth_lvl + 2);
 
                 if let Some(subpattern) = subpattern {
                     print_indented!(self, "subpattern: Some( ", depth_lvl + 2);

compiler/rustc_mir_transform/messages.ftl

@@ -34,12 +34,16 @@ mir_transform_force_inline_attr =
 mir_transform_force_inline_justification =
     `{$callee}` is required to be inlined to: {$sym}
 
+mir_transform_maybe_string_interpolation = you might have meant to use string interpolation in this string literal
+
 mir_transform_must_not_suspend = {$pre}`{$def_path}`{$post} held across a suspend point, but should not be
     .label = the value is held across this suspend point
     .note = {$reason}
     .help = consider using a block (`{"{ ... }"}`) to shrink the value's scope, ending before the suspend point
 mir_transform_operation_will_panic = this operation will panic at runtime
 
+mir_transform_string_interpolation_only_works = string interpolation only works in `format!` invocations
+
 mir_transform_tail_expr_drop_order = relative drop order changing in Rust 2024
     .temporaries = in Rust 2024, this temporary value will be dropped first
     .observers = in Rust 2024, this local variable or temporary value will be dropped second
@@ -77,3 +81,28 @@ mir_transform_unconditional_recursion = function cannot return without recursing
 mir_transform_unconditional_recursion_call_site_label = recursive call site
 
 mir_transform_unknown_pass_name = MIR pass `{$name}` is unknown and will be ignored
+
+mir_transform_unused_assign = value assigned to `{$name}` is never read
+    .help = maybe it is overwritten before being read?
+
+mir_transform_unused_assign_passed = value passed to `{$name}` is never read
+    .help = maybe it is overwritten before being read?
+
+mir_transform_unused_assign_suggestion =
+    you might have meant to mutate the pointed at value being passed in, instead of changing the reference in the local binding
+
+mir_transform_unused_capture_maybe_capture_ref = value captured by `{$name}` is never read
+    .help = did you mean to capture by reference instead?
+
+mir_transform_unused_var_assigned_only = variable `{$name}` is assigned to, but never used
+    .note = consider using `_{$name}` instead
+
+mir_transform_unused_var_underscore = if this is intentional, prefix it with an underscore
+
+mir_transform_unused_variable = unused variable: `{$name}`
+
+mir_transform_unused_variable_args_in_macro = `{$name}` is captured in macro and introduced a unused variable
+
+mir_transform_unused_variable_try_ignore = try ignoring the field
+
+mir_transform_unused_variable_typo = you might have meant to pattern match on the similarly named {$kind} `{$item_name}`

compiler/rustc_mir_transform/src/errors.rs

@@ -1,5 +1,5 @@
 use rustc_errors::codes::*;
-use rustc_errors::{Diag, LintDiagnostic};
+use rustc_errors::{Applicability, Diag, EmissionGuarantee, LintDiagnostic, Subdiagnostic};
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::mir::AssertKind;
 use rustc_middle::query::Key;
@@ -158,6 +158,132 @@ pub(crate) struct FnItemRef {
     pub ident: Ident,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(mir_transform_unused_capture_maybe_capture_ref)]
+#[help]
+pub(crate) struct UnusedCaptureMaybeCaptureRef {
+    pub name: Symbol,
+}
+
+#[derive(LintDiagnostic)]
+#[diag(mir_transform_unused_var_assigned_only)]
+#[note]
+pub(crate) struct UnusedVarAssignedOnly {
+    pub name: Symbol,
+    #[subdiagnostic]
+    pub typo: Option<PatternTypo>,
+}
+
+#[derive(LintDiagnostic)]
+#[diag(mir_transform_unused_assign)]
+pub(crate) struct UnusedAssign {
+    pub name: Symbol,
+    #[subdiagnostic]
+    pub suggestion: Option<UnusedAssignSuggestion>,
+    #[help]
+    pub help: bool,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(mir_transform_unused_assign_suggestion, applicability = "maybe-incorrect")]
+pub(crate) struct UnusedAssignSuggestion {
+    pub pre: &'static str,
+    #[suggestion_part(code = "{pre}mut ")]
+    pub ty_span: Option<Span>,
+    #[suggestion_part(code = "")]
+    pub ty_ref_span: Span,
+    #[suggestion_part(code = "*")]
+    pub pre_lhs_span: Span,
+    #[suggestion_part(code = "")]
+    pub rhs_borrow_span: Span,
+}
+
+#[derive(LintDiagnostic)]
+#[diag(mir_transform_unused_assign_passed)]
+#[help]
+pub(crate) struct UnusedAssignPassed {
+    pub name: Symbol,
+}
+
+#[derive(LintDiagnostic)]
+#[diag(mir_transform_unused_variable)]
+pub(crate) struct UnusedVariable {
+    pub name: Symbol,
+    #[subdiagnostic]
+    pub string_interp: Vec<UnusedVariableStringInterp>,
+    #[subdiagnostic]
+    pub sugg: UnusedVariableSugg,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum UnusedVariableSugg {
+    #[multipart_suggestion(
+        mir_transform_unused_variable_try_ignore,
+        applicability = "machine-applicable"
+    )]
+    TryIgnore {
+        #[suggestion_part(code = "{name}: _")]
+        shorthands: Vec<Span>,
+        #[suggestion_part(code = "_")]
+        non_shorthands: Vec<Span>,
+        name: Symbol,
+    },
+
+    #[multipart_suggestion(
+        mir_transform_unused_var_underscore,
+        applicability = "machine-applicable"
+    )]
+    TryPrefix {
+        #[suggestion_part(code = "_{name}")]
+        spans: Vec<Span>,
+        name: Symbol,
+        #[subdiagnostic]
+        typo: Option<PatternTypo>,
+    },
+
+    #[help(mir_transform_unused_variable_args_in_macro)]
+    NoSugg {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+    },
+}
+
+pub(crate) struct UnusedVariableStringInterp {
+    pub lit: Span,
+}
+
+impl Subdiagnostic for UnusedVariableStringInterp {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
+        diag.span_label(
+            self.lit,
+            crate::fluent_generated::mir_transform_maybe_string_interpolation,
+        );
+        diag.multipart_suggestion(
+            crate::fluent_generated::mir_transform_string_interpolation_only_works,
+            vec![
+                (self.lit.shrink_to_lo(), String::from("format!(")),
+                (self.lit.shrink_to_hi(), String::from(")")),
+            ],
+            Applicability::MachineApplicable,
+        );
+    }
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(
+    mir_transform_unused_variable_typo,
+    style = "verbose",
+    applicability = "maybe-incorrect"
+)]
+pub(crate) struct PatternTypo {
+    #[suggestion_part(code = "{code}")]
+    pub span: Span,
+    pub code: String,
+    pub item_name: Symbol,
+    pub kind: &'static str,
+}
+
 pub(crate) struct MustNotSupend<'a, 'tcx> {
     pub tcx: TyCtxt<'tcx>,
     pub yield_sp: Span,

compiler/rustc_mir_transform/src/lib.rs

@@ -51,6 +51,7 @@
 mod ffi_unwind_calls;
 mod lint;
 mod lint_tail_expr_drop_order;
+mod liveness;
 mod patch;
 mod shim;
 mod ssa;
@@ -216,6 +217,7 @@ pub fn provide(providers: &mut Providers) {
         mir_for_ctfe,
         mir_coroutine_witnesses: coroutine::mir_coroutine_witnesses,
         optimized_mir,
+        check_liveness: liveness::check_liveness,
         is_mir_available,
         is_ctfe_mir_available: is_mir_available,
         mir_callgraph_cyclic: inline::cycle::mir_callgraph_cyclic,
@@ -513,6 +515,8 @@ fn mir_drops_elaborated_and_const_checked(tcx: TyCtxt<'_>, def: LocalDefId) -> &
         }
     }
 
+    tcx.ensure_done().check_liveness(def);
+
     let (body, _) = tcx.mir_promoted(def);
     let mut body = body.steal();
 

compiler/rustc_mir_transform/src/liveness.rs

@@ -0,0 +1,1401 @@
+use rustc_abi::FieldIdx;
+use rustc_data_structures::fx::{FxHashSet, FxIndexMap, IndexEntry};
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::def::{CtorKind, DefKind};
+use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::find_attr;
+use rustc_index::IndexVec;
+use rustc_index::bit_set::DenseBitSet;
+use rustc_middle::bug;
+use rustc_middle::mir::visit::{
+    MutatingUseContext, NonMutatingUseContext, NonUseContext, PlaceContext, Visitor,
+};
+use rustc_middle::mir::*;
+use rustc_middle::ty::print::with_no_trimmed_paths;
+use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_mir_dataflow::fmt::DebugWithContext;
+use rustc_mir_dataflow::{Analysis, Backward, ResultsCursor};
+use rustc_session::lint;
+use rustc_span::Span;
+use rustc_span::edit_distance::find_best_match_for_name;
+use rustc_span::symbol::{Symbol, kw, sym};
+
+use crate::errors;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum AccessKind {
+    Param,
+    Assign,
+    Capture,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum CaptureKind {
+    Closure(ty::ClosureKind),
+    Coroutine,
+    CoroutineClosure,
+    None,
+}
+
+#[derive(Copy, Clone, Debug)]
+struct Access {
+    /// Describe the current access.
+    kind: AccessKind,
+    /// Is the accessed place is live at the current statement?
+    /// When we encounter multiple statements at the same location, we only increase the liveness,
+    /// in order to avoid false positives.
+    live: bool,
+}
+
+#[tracing::instrument(level = "debug", skip(tcx), ret)]
+pub(crate) fn check_liveness<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> DenseBitSet<FieldIdx> {
+    // Don't run on synthetic MIR, as that will ICE trying to access HIR.
+    if tcx.is_synthetic_mir(def_id) {
+        return DenseBitSet::new_empty(0);
+    }
+
+    // Don't run unused pass for intrinsics
+    if tcx.intrinsic(def_id.to_def_id()).is_some() {
+        return DenseBitSet::new_empty(0);
+    }
+
+    // Don't run unused pass for #[naked]
+    if find_attr!(tcx.get_all_attrs(def_id.to_def_id()), AttributeKind::Naked(..)) {
+        return DenseBitSet::new_empty(0);
+    }
+
+    // Don't run unused pass for #[derive]
+    let parent = tcx.parent(tcx.typeck_root_def_id(def_id.to_def_id()));
+    if let DefKind::Impl { of_trait: true } = tcx.def_kind(parent)
+        && find_attr!(tcx.get_all_attrs(parent), AttributeKind::AutomaticallyDerived(..))
+    {
+        return DenseBitSet::new_empty(0);
+    }
+
+    let mut body = &*tcx.mir_promoted(def_id).0.borrow();
+    let mut body_mem;
+
+    // Don't run if there are errors.
+    if body.tainted_by_errors.is_some() {
+        return DenseBitSet::new_empty(0);
+    }
+
+    let mut checked_places = PlaceSet::default();
+    checked_places.insert_locals(&body.local_decls);
+
+    // The body is the one of a closure or generator, so we also want to analyse captures.
+    let (capture_kind, num_captures) = if tcx.is_closure_like(def_id.to_def_id()) {
+        let mut self_ty = body.local_decls[ty::CAPTURE_STRUCT_LOCAL].ty;
+        let mut self_is_ref = false;
+        if let ty::Ref(_, ty, _) = self_ty.kind() {
+            self_ty = *ty;
+            self_is_ref = true;
+        }
+
+        let (capture_kind, args) = match self_ty.kind() {
+            ty::Closure(_, args) => {
+                (CaptureKind::Closure(args.as_closure().kind()), ty::UpvarArgs::Closure(args))
+            }
+            &ty::Coroutine(_, args) => (CaptureKind::Coroutine, ty::UpvarArgs::Coroutine(args)),
+            &ty::CoroutineClosure(_, args) => {
+                (CaptureKind::CoroutineClosure, ty::UpvarArgs::CoroutineClosure(args))
+            }
+            _ => bug!("expected closure or generator, found {:?}", self_ty),
+        };
+
+        let captures = tcx.closure_captures(def_id);
+        checked_places.insert_captures(tcx, self_is_ref, captures, args.upvar_tys());
+
+        // `FnMut` closures can modify captured values and carry those
+        // modified values with them in subsequent calls. To model this behaviour,
+        // we consider the `FnMut` closure as jumping to `bb0` upon return.
+        if let CaptureKind::Closure(ty::ClosureKind::FnMut) = capture_kind {
+            // FIXME: stop cloning the body.
+            body_mem = body.clone();
+            for bbdata in body_mem.basic_blocks_mut() {
+                // We can call a closure again, either after a normal return or an unwind.
+                if let TerminatorKind::Return | TerminatorKind::UnwindResume =
+                    bbdata.terminator().kind
+                {
+                    bbdata.terminator_mut().kind = TerminatorKind::Goto { target: START_BLOCK };
+                }
+            }
+            body = &body_mem;
+        }
+
+        (capture_kind, args.upvar_tys().len())
+    } else {
+        (CaptureKind::None, 0)
+    };
+
+    // Get the remaining variables' names from debuginfo.
+    checked_places.record_debuginfo(&body.var_debug_info);
+
+    let self_assignment = find_self_assignments(&checked_places, body);
+
+    let mut live =
+        MaybeLivePlaces { tcx, capture_kind, checked_places: &checked_places, self_assignment }
+            .iterate_to_fixpoint(tcx, body, None)
+            .into_results_cursor(body);
+
+    let typing_env = ty::TypingEnv::post_analysis(tcx, body.source.def_id());
+
+    let mut assignments =
+        AssignmentResult::find_dead_assignments(tcx, typing_env, &checked_places, &mut live, body);
+
+    assignments.merge_guards();
+
+    let dead_captures = assignments.compute_dead_captures(num_captures);
+
+    assignments.report_fully_unused();
+    assignments.report_unused_assignments();
+
+    dead_captures
+}
+
+/// Small helper to make semantics easier to read.
+#[inline]
+fn is_capture(place: PlaceRef<'_>) -> bool {
+    if !place.projection.is_empty() {
+        debug_assert_eq!(place.local, ty::CAPTURE_STRUCT_LOCAL);
+        true
+    } else {
+        false
+    }
+}
+
+/// Give a diagnostic when any of the string constants look like a naked format string that would
+/// interpolate our dead local.
+fn maybe_suggest_literal_matching_name(
+    body: &Body<'_>,
+    name: Symbol,
+) -> Vec<errors::UnusedVariableStringInterp> {
+    struct LiteralFinder<'body, 'tcx> {
+        body: &'body Body<'tcx>,
+        name: String,
+        name_colon: String,
+        found: Vec<errors::UnusedVariableStringInterp>,
+    }
+
+    impl<'tcx> Visitor<'tcx> for LiteralFinder<'_, 'tcx> {
+        fn visit_const_operand(&mut self, constant: &ConstOperand<'tcx>, loc: Location) {
+            if let ty::Ref(_, ref_ty, _) = constant.ty().kind()
+                && ref_ty.kind() == &ty::Str
+            {
+                let rendered_constant = constant.const_.to_string();
+                if rendered_constant.contains(&self.name)
+                    || rendered_constant.contains(&self.name_colon)
+                {
+                    let lit = self.body.source_info(loc).span;
+                    self.found.push(errors::UnusedVariableStringInterp { lit });
+                }
+            }
+        }
+    }
+
+    let mut finder = LiteralFinder {
+        body,
+        name: format!("{{{name}}}"),
+        name_colon: format!("{{{name}:"),
+        found: vec![],
+    };
+    finder.visit_body(body);
+    finder.found
+}
+
+/// Give a diagnostic when an unused variable may be a typo of a unit variant or a struct.
+fn maybe_suggest_unit_pattern_typo<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    body_def_id: DefId,
+    name: Symbol,
+    span: Span,
+    ty: Ty<'tcx>,
+) -> Option<errors::PatternTypo> {
+    if let ty::Adt(adt_def, _) = ty.peel_refs().kind() {
+        let variant_names: Vec<_> = adt_def
+            .variants()
+            .iter()
+            .filter(|v| matches!(v.ctor, Some((CtorKind::Const, _))))
+            .map(|v| v.name)
+            .collect();
+        if let Some(name) = find_best_match_for_name(&variant_names, name, None)
+            && let Some(variant) = adt_def
+                .variants()
+                .iter()
+                .find(|v| v.name == name && matches!(v.ctor, Some((CtorKind::Const, _))))
+        {
+            return Some(errors::PatternTypo {
+                span,
+                code: with_no_trimmed_paths!(tcx.def_path_str(variant.def_id)),
+                kind: tcx.def_descr(variant.def_id),
+                item_name: variant.name,
+            });
+        }
+    }
+
+    // Look for consts of the same type with similar names as well,
+    // not just unit structs and variants.
+    let constants = tcx
+        .hir_body_owners()
+        .filter(|&def_id| {
+            matches!(tcx.def_kind(def_id), DefKind::Const)
+                && tcx.type_of(def_id).instantiate_identity() == ty
+                && tcx.visibility(def_id).is_accessible_from(body_def_id, tcx)
+        })
+        .collect::<Vec<_>>();
+    let names = constants.iter().map(|&def_id| tcx.item_name(def_id)).collect::<Vec<_>>();
+    if let Some(item_name) = find_best_match_for_name(&names, name, None)
+        && let Some(position) = names.iter().position(|&n| n == item_name)
+        && let Some(&def_id) = constants.get(position)
+    {
+        return Some(errors::PatternTypo {
+            span,
+            code: with_no_trimmed_paths!(tcx.def_path_str(def_id)),
+            kind: "constant",
+            item_name,
+        });
+    }
+
+    None
+}
+
+/// Return whether we should consider the current place as a drop guard and skip reporting.
+fn maybe_drop_guard<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    typing_env: ty::TypingEnv<'tcx>,
+    index: PlaceIndex,
+    ever_dropped: &DenseBitSet<PlaceIndex>,
+    checked_places: &PlaceSet<'tcx>,
+    body: &Body<'tcx>,
+) -> bool {
+    if ever_dropped.contains(index) {
+        let ty = checked_places.places[index].ty(&body.local_decls, tcx).ty;
+        matches!(
+            ty.kind(),
+            ty::Closure(..)
+                | ty::Coroutine(..)
+                | ty::Tuple(..)
+                | ty::Adt(..)
+                | ty::Dynamic(..)
+                | ty::Array(..)
+                | ty::Slice(..)
+                | ty::Alias(ty::Opaque, ..)
+        ) && ty.needs_drop(tcx, typing_env)
+    } else {
+        false
+    }
+}
+
+/// Detect the following case
+///
+/// ```text
+/// fn change_object(mut a: &Ty) {
+///     let a = Ty::new();
+///     b = &a;
+/// }
+/// ```
+///
+/// where the user likely meant to modify the value behind there reference, use `a` as an out
+/// parameter, instead of mutating the local binding. When encountering this we suggest:
+///
+/// ```text
+/// fn change_object(a: &'_ mut Ty) {
+///     let a = Ty::new();
+///     *b = a;
+/// }
+/// ```
+fn annotate_mut_binding_to_immutable_binding<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    place: PlaceRef<'tcx>,
+    body_def_id: LocalDefId,
+    assignment_span: Span,
+    body: &Body<'tcx>,
+) -> Option<errors::UnusedAssignSuggestion> {
+    use rustc_hir as hir;
+    use rustc_hir::intravisit::{self, Visitor};
+
+    // Verify we have a mutable argument...
+    let local = place.as_local()?;
+    let LocalKind::Arg = body.local_kind(local) else { return None };
+    let Mutability::Mut = body.local_decls[local].mutability else { return None };
+
+    // ... with reference type...
+    let hir_param_index =
+        local.as_usize() - if tcx.is_closure_like(body_def_id.to_def_id()) { 2 } else { 1 };
+    let fn_decl = tcx.hir_node_by_def_id(body_def_id).fn_decl()?;
+    let ty = fn_decl.inputs[hir_param_index];
+    let hir::TyKind::Ref(lt, mut_ty) = ty.kind else { return None };
+
+    // ... as a binding pattern.
+    let hir_body = tcx.hir_maybe_body_owned_by(body_def_id)?;
+    let param = hir_body.params[hir_param_index];
+    let hir::PatKind::Binding(hir::BindingMode::MUT, _hir_id, ident, _) = param.pat.kind else {
+        return None;
+    };
+
+    // Find the assignment to modify.
+    let mut finder = ExprFinder { assignment_span, lhs: None, rhs: None };
+    finder.visit_body(hir_body);
+    let lhs = finder.lhs?;
+    let rhs = finder.rhs?;
+
+    let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _mut, inner) = rhs.kind else { return None };
+
+    // Changes to the parameter's type.
+    let pre = if lt.ident.span.is_empty() { "" } else { " " };
+    let ty_span = if mut_ty.mutbl.is_mut() {
+        // Leave `&'name mut Ty` and `&mut Ty` as they are (#136028).
+        None
+    } else {
+        // `&'name Ty` -> `&'name mut Ty` or `&Ty` -> `&mut Ty`
+        Some(mut_ty.ty.span.shrink_to_lo())
+    };
+
+    return Some(errors::UnusedAssignSuggestion {
+        ty_span,
+        pre,
+        // Span of the `mut` before the binding.
+        ty_ref_span: param.pat.span.until(ident.span),
+        // Where to add a `*`.
+        pre_lhs_span: lhs.span.shrink_to_lo(),
+        // Where to remove the borrow.
+        rhs_borrow_span: rhs.span.until(inner.span),
+    });
+
+    #[derive(Debug)]
+    struct ExprFinder<'hir> {
+        assignment_span: Span,
+        lhs: Option<&'hir hir::Expr<'hir>>,
+        rhs: Option<&'hir hir::Expr<'hir>>,
+    }
+    impl<'hir> Visitor<'hir> for ExprFinder<'hir> {
+        fn visit_expr(&mut self, expr: &'hir hir::Expr<'hir>) {
+            if expr.span == self.assignment_span
+                && let hir::ExprKind::Assign(lhs, rhs, _) = expr.kind
+            {
+                self.lhs = Some(lhs);
+                self.rhs = Some(rhs);
+            } else {
+                intravisit::walk_expr(self, expr)
+            }
+        }
+    }
+}
+
+/// Compute self-assignments of the form `a += b`.
+///
+/// MIR building generates 2 statements and 1 terminator for such assignments:
+/// - _temp = CheckedBinaryOp(a, b)
+/// - assert(!_temp.1)
+/// - a = _temp.0
+///
+/// This function tries to detect this pattern in order to avoid marking statement as a definition
+/// and use. This will let the analysis be dictated by the next use of `a`.
+///
+/// Note that we will still need to account for the use of `b`.
+fn find_self_assignments<'tcx>(
+    checked_places: &PlaceSet<'tcx>,
+    body: &Body<'tcx>,
+) -> FxHashSet<Location> {
+    let mut self_assign = FxHashSet::default();
+
+    const FIELD_0: FieldIdx = FieldIdx::from_u32(0);
+    const FIELD_1: FieldIdx = FieldIdx::from_u32(1);
+
+    for (bb, bb_data) in body.basic_blocks.iter_enumerated() {
+        for (statement_index, stmt) in bb_data.statements.iter().enumerate() {
+            let StatementKind::Assign(box (first_place, rvalue)) = &stmt.kind else { continue };
+            match rvalue {
+                // For checked binary ops, the MIR builder inserts an assertion in between.
+                Rvalue::BinaryOp(
+                    BinOp::AddWithOverflow | BinOp::SubWithOverflow | BinOp::MulWithOverflow,
+                    box (Operand::Copy(lhs), _),
+                ) => {
+                    // Checked binary ops only appear at the end of the block, before the assertion.
+                    if statement_index + 1 != bb_data.statements.len() {
+                        continue;
+                    }
+
+                    let TerminatorKind::Assert {
+                        cond,
+                        target,
+                        msg: box AssertKind::Overflow(..),
+                        ..
+                    } = &bb_data.terminator().kind
+                    else {
+                        continue;
+                    };
+                    let Some(assign) = body.basic_blocks[*target].statements.first() else {
+                        continue;
+                    };
+                    let StatementKind::Assign(box (dest, Rvalue::Use(Operand::Move(temp)))) =
+                        assign.kind
+                    else {
+                        continue;
+                    };
+
+                    if dest != *lhs {
+                        continue;
+                    }
+
+                    let Operand::Move(cond) = cond else { continue };
+                    let [PlaceElem::Field(FIELD_0, _)] = &temp.projection.as_slice() else {
+                        continue;
+                    };
+                    let [PlaceElem::Field(FIELD_1, _)] = &cond.projection.as_slice() else {
+                        continue;
+                    };
+
+                    // We ignore indirect self-assignment, because both occurrences of `dest` are uses.
+                    let is_indirect = checked_places
+                        .get(dest.as_ref())
+                        .map_or(false, |(_, projections)| is_indirect(projections));
+                    if is_indirect {
+                        continue;
+                    }
+
+                    if first_place.local == temp.local
+                        && first_place.local == cond.local
+                        && first_place.projection.is_empty()
+                    {
+                        // Original block
+                        self_assign.insert(Location {
+                            block: bb,
+                            statement_index: bb_data.statements.len() - 1,
+                        });
+                        self_assign.insert(Location {
+                            block: bb,
+                            statement_index: bb_data.statements.len(),
+                        });
+                        // Target block
+                        self_assign.insert(Location { block: *target, statement_index: 0 });
+                    }
+                }
+                // Straight self-assignment.
+                Rvalue::BinaryOp(op, box (Operand::Copy(lhs), _)) => {
+                    if lhs != first_place {
+                        continue;
+                    }
+
+                    // We ignore indirect self-assignment, because both occurrences of `dest` are uses.
+                    let is_indirect = checked_places
+                        .get(first_place.as_ref())
+                        .map_or(false, |(_, projections)| is_indirect(projections));
+                    if is_indirect {
+                        continue;
+                    }
+
+                    self_assign.insert(Location { block: bb, statement_index });
+
+                    // Checked division verifies overflow before performing the division, so we
+                    // need to go and ignore this check in the predecessor block.
+                    if let BinOp::Div | BinOp::Rem = op
+                        && statement_index == 0
+                        && let &[pred] = body.basic_blocks.predecessors()[bb].as_slice()
+                        && let TerminatorKind::Assert { msg, .. } =
+                            &body.basic_blocks[pred].terminator().kind
+                        && let AssertKind::Overflow(..) = **msg
+                        && let len = body.basic_blocks[pred].statements.len()
+                        && len >= 2
+                    {
+                        // BitAnd of two checks.
+                        self_assign.insert(Location { block: pred, statement_index: len - 1 });
+                        // `lhs == MIN`.
+                        self_assign.insert(Location { block: pred, statement_index: len - 2 });
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+
+    self_assign
+}
+
+#[derive(Default, Debug)]
+struct PlaceSet<'tcx> {
+    places: IndexVec<PlaceIndex, PlaceRef<'tcx>>,
+    names: IndexVec<PlaceIndex, Option<(Symbol, Span)>>,
+
+    /// Places corresponding to locals, common case.
+    locals: IndexVec<Local, Option<PlaceIndex>>,
+
+    // Handling of captures.
+    /// If `_1` is a reference, we need to add a `Deref` to the matched place.
+    capture_field_pos: usize,
+    /// Captured fields.
+    captures: IndexVec<FieldIdx, (PlaceIndex, bool)>,
+}
+
+impl<'tcx> PlaceSet<'tcx> {
+    fn insert_locals(&mut self, decls: &IndexVec<Local, LocalDecl<'tcx>>) {
+        self.locals = IndexVec::from_elem(None, &decls);
+        for (local, decl) in decls.iter_enumerated() {
+            // Record all user-written locals for the analysis.
+            // We also keep the `RefForGuard` locals (more on that below).
+            if let LocalInfo::User(BindingForm::Var(_) | BindingForm::RefForGuard(_)) =
+                decl.local_info()
+            {
+                let index = self.places.push(local.into());
+                self.locals[local] = Some(index);
+                let _index = self.names.push(None);
+                debug_assert_eq!(index, _index);
+            }
+        }
+    }
+
+    fn insert_captures(
+        &mut self,
+        tcx: TyCtxt<'tcx>,
+        self_is_ref: bool,
+        captures: &[&'tcx ty::CapturedPlace<'tcx>],
+        upvars: &ty::List<Ty<'tcx>>,
+    ) {
+        // We should not track the environment local separately.
+        debug_assert_eq!(self.locals[ty::CAPTURE_STRUCT_LOCAL], None);
+
+        let self_place = Place {
+            local: ty::CAPTURE_STRUCT_LOCAL,
+            projection: tcx.mk_place_elems(if self_is_ref { &[PlaceElem::Deref] } else { &[] }),
+        };
+        if self_is_ref {
+            self.capture_field_pos = 1;
+        }
+
+        for (f, (capture, ty)) in std::iter::zip(captures, upvars).enumerate() {
+            let f = FieldIdx::from_usize(f);
+            let elem = PlaceElem::Field(f, ty);
+            let by_ref = matches!(capture.info.capture_kind, ty::UpvarCapture::ByRef(..));
+            let place = if by_ref {
+                self_place.project_deeper(&[elem, PlaceElem::Deref], tcx)
+            } else {
+                self_place.project_deeper(&[elem], tcx)
+            };
+            let index = self.places.push(place.as_ref());
+            let _f = self.captures.push((index, by_ref));
+            debug_assert_eq!(_f, f);
+
+            // Record a variable name from the capture, because it is much friendlier than the
+            // debuginfo name.
+            self.names.insert(
+                index,
+                (Symbol::intern(&capture.to_string(tcx)), capture.get_path_span(tcx)),
+            );
+        }
+    }
+
+    fn record_debuginfo(&mut self, var_debug_info: &Vec<VarDebugInfo<'tcx>>) {
+        let ignore_name = |name: Symbol| {
+            name == sym::empty || name == kw::SelfLower || name.as_str().starts_with('_')
+        };
+        for var_debug_info in var_debug_info {
+            if let VarDebugInfoContents::Place(place) = var_debug_info.value
+                && let Some(index) = self.locals[place.local]
+                && !ignore_name(var_debug_info.name)
+            {
+                self.names.get_or_insert_with(index, || {
+                    (var_debug_info.name, var_debug_info.source_info.span)
+                });
+            }
+        }
+
+        // Discard places that will not result in a diagnostic.
+        for index_opt in self.locals.iter_mut() {
+            if let Some(index) = *index_opt {
+                let remove = match self.names[index] {
+                    None => true,
+                    Some((name, _)) => ignore_name(name),
+                };
+                if remove {
+                    *index_opt = None;
+                }
+            }
+        }
+    }
+
+    #[inline]
+    fn get(&self, place: PlaceRef<'tcx>) -> Option<(PlaceIndex, &'tcx [PlaceElem<'tcx>])> {
+        if let Some(index) = self.locals[place.local] {
+            return Some((index, place.projection));
+        }
+        if place.local == ty::CAPTURE_STRUCT_LOCAL
+            && !self.captures.is_empty()
+            && self.capture_field_pos < place.projection.len()
+            && let PlaceElem::Field(f, _) = place.projection[self.capture_field_pos]
+            && let Some((index, by_ref)) = self.captures.get(f)
+        {
+            let mut start = self.capture_field_pos + 1;
+            if *by_ref {
+                // Account for an extra Deref.
+                start += 1;
+            }
+            // We may have an attempt to access `_1.f` as a shallow reborrow. Just ignore it.
+            if start <= place.projection.len() {
+                let projection = &place.projection[start..];
+                return Some((*index, projection));
+            }
+        }
+        None
+    }
+
+    fn iter(&self) -> impl Iterator<Item = (PlaceIndex, &PlaceRef<'tcx>)> {
+        self.places.iter_enumerated()
+    }
+
+    fn len(&self) -> usize {
+        self.places.len()
+    }
+}
+
+struct AssignmentResult<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    typing_env: ty::TypingEnv<'tcx>,
+    checked_places: &'a PlaceSet<'tcx>,
+    body: &'a Body<'tcx>,
+    /// Set of locals that are live at least once. This is used to report fully unused locals.
+    ever_live: DenseBitSet<PlaceIndex>,
+    /// Set of locals that have a non-trivial drop. This is used to skip reporting unused
+    /// assignment if it would be used by the `Drop` impl.
+    ever_dropped: DenseBitSet<PlaceIndex>,
+    /// Set of assignments for each local. Here, assignment is understood in the AST sense. Any
+    /// MIR that may look like an assignment (Assign, DropAndReplace, Yield, Call) are considered.
+    ///
+    /// For each local, we return a map: for each source position, whether the statement is live
+    /// and which kind of access it performs. When we encounter multiple statements at the same
+    /// location, we only increase the liveness, in order to avoid false positives.
+    assignments: IndexVec<PlaceIndex, FxIndexMap<SourceInfo, Access>>,
+}
+
+impl<'a, 'tcx> AssignmentResult<'a, 'tcx> {
+    /// Collect all assignments to checked locals.
+    ///
+    /// Assignments are collected, even if they are live. Dead assignments are reported, and live
+    /// assignments are used to make diagnostics correct for match guards.
+    fn find_dead_assignments(
+        tcx: TyCtxt<'tcx>,
+        typing_env: ty::TypingEnv<'tcx>,
+        checked_places: &'a PlaceSet<'tcx>,
+        cursor: &mut ResultsCursor<'_, 'tcx, MaybeLivePlaces<'_, 'tcx>>,
+        body: &'a Body<'tcx>,
+    ) -> AssignmentResult<'a, 'tcx> {
+        let mut ever_live = DenseBitSet::new_empty(checked_places.len());
+        let mut ever_dropped = DenseBitSet::new_empty(checked_places.len());
+        let mut assignments = IndexVec::<PlaceIndex, FxIndexMap<_, _>>::from_elem(
+            Default::default(),
+            &checked_places.places,
+        );
+
+        let mut check_place =
+            |place: Place<'tcx>, kind, source_info: SourceInfo, live: &DenseBitSet<PlaceIndex>| {
+                if let Some((index, extra_projections)) = checked_places.get(place.as_ref()) {
+                    if !is_indirect(extra_projections) {
+                        match assignments[index].entry(source_info) {
+                            IndexEntry::Vacant(v) => {
+                                let access = Access { kind, live: live.contains(index) };
+                                v.insert(access);
+                            }
+                            IndexEntry::Occupied(mut o) => {
+                                // There were already a sighting. Mark this statement as live if it
+                                // was, to avoid false positives.
+                                o.get_mut().live |= live.contains(index);
+                            }
+                        }
+                    }
+                }
+            };
+
+        let mut record_drop = |place: Place<'tcx>| {
+            if let Some((index, &[])) = checked_places.get(place.as_ref()) {
+                ever_dropped.insert(index);
+            }
+        };
+
+        for (bb, bb_data) in traversal::postorder(body) {
+            cursor.seek_to_block_end(bb);
+            let live = cursor.get();
+            ever_live.union(live);
+
+            let terminator = bb_data.terminator();
+            match &terminator.kind {
+                TerminatorKind::Call { destination: place, .. }
+                | TerminatorKind::Yield { resume_arg: place, .. } => {
+                    check_place(*place, AccessKind::Assign, terminator.source_info, live);
+                    record_drop(*place)
+                }
+                TerminatorKind::Drop { place, .. } => record_drop(*place),
+                TerminatorKind::InlineAsm { operands, .. } => {
+                    for operand in operands {
+                        if let InlineAsmOperand::Out { place: Some(place), .. }
+                        | InlineAsmOperand::InOut { out_place: Some(place), .. } = operand
+                        {
+                            check_place(*place, AccessKind::Assign, terminator.source_info, live);
+                        }
+                    }
+                }
+                _ => {}
+            }
+
+            for (statement_index, statement) in bb_data.statements.iter().enumerate().rev() {
+                cursor.seek_before_primary_effect(Location { block: bb, statement_index });
+                let live = cursor.get();
+                ever_live.union(live);
+                match &statement.kind {
+                    StatementKind::Assign(box (place, _))
+                    | StatementKind::SetDiscriminant { box place, .. } => {
+                        check_place(*place, AccessKind::Assign, statement.source_info, live);
+                    }
+                    StatementKind::Retag(_, _)
+                    | StatementKind::StorageLive(_)
+                    | StatementKind::StorageDead(_)
+                    | StatementKind::Coverage(_)
+                    | StatementKind::Intrinsic(_)
+                    | StatementKind::Nop
+                    | StatementKind::FakeRead(_)
+                    | StatementKind::PlaceMention(_)
+                    | StatementKind::ConstEvalCounter
+                    | StatementKind::BackwardIncompatibleDropHint { .. }
+                    | StatementKind::AscribeUserType(_, _) => (),
+                }
+            }
+        }
+
+        // Check liveness of function arguments on entry.
+        {
+            cursor.seek_to_block_start(START_BLOCK);
+            let live = cursor.get();
+            ever_live.union(live);
+
+            // Verify that arguments and captured values are useful.
+            for (index, place) in checked_places.iter() {
+                let kind = if is_capture(*place) {
+                    // This is a by-ref capture, an assignment to it will modify surrounding
+                    // environment, so we do not report it.
+                    if place.projection.last() == Some(&PlaceElem::Deref) {
+                        continue;
+                    }
+
+                    AccessKind::Capture
+                } else if body.local_kind(place.local) == LocalKind::Arg {
+                    AccessKind::Param
+                } else {
+                    continue;
+                };
+                let source_info = body.local_decls[place.local].source_info;
+                let access = Access { kind, live: live.contains(index) };
+                assignments[index].insert(source_info, access);
+            }
+        }
+
+        AssignmentResult {
+            tcx,
+            typing_env,
+            checked_places,
+            ever_live,
+            ever_dropped,
+            assignments,
+            body,
+        }
+    }
+
+    /// Match guards introduce a different local to freeze the guarded value as immutable.
+    /// Having two locals, we need to make sure that we do not report an unused_variable
+    /// when the guard local is used but not the arm local, or vice versa, like in this example.
+    ///
+    ///    match 5 {
+    ///      x if x > 2 => {}
+    ///      ^    ^- This is `local`
+    ///      +------ This is `arm_local`
+    ///      _ => {}
+    ///    }
+    ///
+    fn merge_guards(&mut self) {
+        for (index, place) in self.checked_places.iter() {
+            let local = place.local;
+            if let &LocalInfo::User(BindingForm::RefForGuard(arm_local)) =
+                self.body.local_decls[local].local_info()
+            {
+                debug_assert!(place.projection.is_empty());
+
+                // Local to use in the arm.
+                let Some((arm_index, _proj)) = self.checked_places.get(arm_local.into()) else {
+                    continue;
+                };
+                debug_assert_ne!(index, arm_index);
+                debug_assert_eq!(_proj, &[]);
+
+                // Mark the arm local as used if the guard local is used.
+                if self.ever_live.contains(index) {
+                    self.ever_live.insert(arm_index);
+                }
+
+                // Some assignments are common to both locals in the source code.
+                // Sadly, we can only detect this using the `source_info`.
+                // Therefore, we loop over all the assignments we have for the guard local:
+                // - if they already appeared for the arm local, the assignment is live if one of the
+                //   two versions is live;
+                // - if it does not appear for the arm local, it happened inside the guard, so we add
+                //   it as-is.
+                let guard_assignments = std::mem::take(&mut self.assignments[index]);
+                let arm_assignments = &mut self.assignments[arm_index];
+                for (source_info, access) in guard_assignments {
+                    match arm_assignments.entry(source_info) {
+                        IndexEntry::Vacant(v) => {
+                            v.insert(access);
+                        }
+                        IndexEntry::Occupied(mut o) => {
+                            o.get_mut().live |= access.live;
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    /// Compute captures that are fully dead.
+    fn compute_dead_captures(&self, num_captures: usize) -> DenseBitSet<FieldIdx> {
+        // Report to caller the set of dead captures.
+        let mut dead_captures = DenseBitSet::new_empty(num_captures);
+        for (index, place) in self.checked_places.iter() {
+            if self.ever_live.contains(index) {
+                continue;
+            }
+
+            // This is a capture: pass information to the enclosing function.
+            if is_capture(*place) {
+                for p in place.projection {
+                    if let PlaceElem::Field(f, _) = p {
+                        dead_captures.insert(*f);
+                        break;
+                    }
+                }
+                continue;
+            }
+        }
+
+        dead_captures
+    }
+
+    /// Report fully unused locals, and forget the corresponding assignments.
+    fn report_fully_unused(&mut self) {
+        let tcx = self.tcx;
+
+        // First, report fully unused locals.
+        for (index, place) in self.checked_places.iter() {
+            if self.ever_live.contains(index) {
+                continue;
+            }
+
+            // this is a capture: let the enclosing function report the unused variable.
+            if is_capture(*place) {
+                continue;
+            }
+
+            let local = place.local;
+            let decl = &self.body.local_decls[local];
+
+            if decl.from_compiler_desugaring() {
+                continue;
+            }
+
+            // Only report actual user-defined binding from now on.
+            let LocalInfo::User(BindingForm::Var(binding)) = decl.local_info() else { continue };
+            let Some(hir_id) = decl.source_info.scope.lint_root(&self.body.source_scopes) else {
+                continue;
+            };
+
+            let introductions = &binding.introductions;
+
+            let Some((name, def_span)) = self.checked_places.names[index] else { continue };
+
+            // #117284, when `ident_span` and `def_span` have different contexts
+            // we can't provide a good suggestion, instead we pointed out the spans from macro
+            let from_macro = def_span.from_expansion()
+                && introductions.iter().any(|intro| intro.span.eq_ctxt(def_span));
+
+            let maybe_suggest_typo = || {
+                if let LocalKind::Arg = self.body.local_kind(local) {
+                    None
+                } else {
+                    maybe_suggest_unit_pattern_typo(
+                        tcx,
+                        self.body.source.def_id(),
+                        name,
+                        def_span,
+                        decl.ty,
+                    )
+                }
+            };
+
+            let statements = &mut self.assignments[index];
+            if statements.is_empty() {
+                let sugg = if from_macro {
+                    errors::UnusedVariableSugg::NoSugg { span: def_span, name }
+                } else {
+                    let typo = maybe_suggest_typo();
+                    errors::UnusedVariableSugg::TryPrefix { spans: vec![def_span], name, typo }
+                };
+                tcx.emit_node_span_lint(
+                    lint::builtin::UNUSED_VARIABLES,
+                    hir_id,
+                    def_span,
+                    errors::UnusedVariable {
+                        name,
+                        string_interp: maybe_suggest_literal_matching_name(self.body, name),
+                        sugg,
+                    },
+                );
+                continue;
+            }
+
+            // Idiomatic rust assigns a value to a local upon definition. However, we do not want to
+            // warn twice, for the unused local and for the unused assignment. Therefore, we remove
+            // from the list of assignments the ones that happen at the definition site.
+            statements.retain(|source_info, _| {
+                source_info.span.find_ancestor_inside(binding.pat_span).is_none()
+            });
+
+            // Extra assignments that we recognize thanks to the initialization span. We need to
+            // take care of macro contexts here to be accurate.
+            if let Some((_, initializer_span)) = binding.opt_match_place {
+                statements.retain(|source_info, _| {
+                    let within = source_info.span.find_ancestor_inside(initializer_span);
+                    let outer_initializer_span =
+                        initializer_span.find_ancestor_in_same_ctxt(source_info.span);
+                    within.is_none()
+                        && outer_initializer_span.map_or(true, |s| !s.contains(source_info.span))
+                });
+            }
+
+            if !statements.is_empty() {
+                // We have a dead local with outstanding assignments and with non-trivial drop.
+                // This is probably a drop-guard, so we do not issue a warning there.
+                if maybe_drop_guard(
+                    tcx,
+                    self.typing_env,
+                    index,
+                    &self.ever_dropped,
+                    self.checked_places,
+                    self.body,
+                ) {
+                    statements.clear();
+                    continue;
+                }
+
+                let typo = maybe_suggest_typo();
+                tcx.emit_node_span_lint(
+                    lint::builtin::UNUSED_VARIABLES,
+                    hir_id,
+                    def_span,
+                    errors::UnusedVarAssignedOnly { name, typo },
+                );
+                continue;
+            }
+
+            // We do not have outstanding assignments, suggest renaming the binding.
+            let spans = introductions.iter().map(|intro| intro.span).collect::<Vec<_>>();
+
+            let any_shorthand = introductions.iter().any(|intro| intro.is_shorthand);
+
+            let sugg = if any_shorthand {
+                errors::UnusedVariableSugg::TryIgnore {
+                    name,
+                    shorthands: introductions
+                        .iter()
+                        .filter_map(
+                            |intro| if intro.is_shorthand { Some(intro.span) } else { None },
+                        )
+                        .collect(),
+                    non_shorthands: introductions
+                        .iter()
+                        .filter_map(
+                            |intro| {
+                                if !intro.is_shorthand { Some(intro.span) } else { None }
+                            },
+                        )
+                        .collect(),
+                }
+            } else if from_macro {
+                errors::UnusedVariableSugg::NoSugg { span: def_span, name }
+            } else if !introductions.is_empty() {
+                let typo = maybe_suggest_typo();
+                errors::UnusedVariableSugg::TryPrefix { name, typo, spans: spans.clone() }
+            } else {
+                let typo = maybe_suggest_typo();
+                errors::UnusedVariableSugg::TryPrefix { name, typo, spans: vec![def_span] }
+            };
+
+            tcx.emit_node_span_lint(
+                lint::builtin::UNUSED_VARIABLES,
+                hir_id,
+                spans,
+                errors::UnusedVariable {
+                    name,
+                    string_interp: maybe_suggest_literal_matching_name(self.body, name),
+                    sugg,
+                },
+            );
+        }
+    }
+
+    /// Second, report unused assignments that do not correspond to initialization.
+    /// Initializations have been removed in the previous loop reporting unused variables.
+    fn report_unused_assignments(self) {
+        let tcx = self.tcx;
+
+        for (index, statements) in self.assignments.into_iter_enumerated() {
+            if statements.is_empty() {
+                continue;
+            }
+
+            let Some((name, decl_span)) = self.checked_places.names[index] else { continue };
+
+            // We have outstanding assignments and with non-trivial drop.
+            // This is probably a drop-guard, so we do not issue a warning there.
+            if maybe_drop_guard(
+                tcx,
+                self.typing_env,
+                index,
+                &self.ever_dropped,
+                self.checked_places,
+                self.body,
+            ) {
+                continue;
+            }
+
+            // We probed MIR in reverse order for dataflow.
+            // We revert the vector to give a consistent order to the user.
+            for (source_info, Access { live, kind }) in statements.into_iter().rev() {
+                if live {
+                    continue;
+                }
+
+                // Report the dead assignment.
+                let Some(hir_id) = source_info.scope.lint_root(&self.body.source_scopes) else {
+                    continue;
+                };
+
+                match kind {
+                    AccessKind::Assign => {
+                        let suggestion = annotate_mut_binding_to_immutable_binding(
+                            tcx,
+                            self.checked_places.places[index],
+                            self.body.source.def_id().expect_local(),
+                            source_info.span,
+                            self.body,
+                        );
+                        tcx.emit_node_span_lint(
+                            lint::builtin::UNUSED_ASSIGNMENTS,
+                            hir_id,
+                            source_info.span,
+                            errors::UnusedAssign { name, help: suggestion.is_none(), suggestion },
+                        )
+                    }
+                    AccessKind::Param => tcx.emit_node_span_lint(
+                        lint::builtin::UNUSED_ASSIGNMENTS,
+                        hir_id,
+                        source_info.span,
+                        errors::UnusedAssignPassed { name },
+                    ),
+                    AccessKind::Capture => tcx.emit_node_span_lint(
+                        lint::builtin::UNUSED_ASSIGNMENTS,
+                        hir_id,
+                        decl_span,
+                        errors::UnusedCaptureMaybeCaptureRef { name },
+                    ),
+                }
+            }
+        }
+    }
+}
+
+rustc_index::newtype_index! {
+    pub struct PlaceIndex {}
+}
+
+impl DebugWithContext<MaybeLivePlaces<'_, '_>> for PlaceIndex {
+    fn fmt_with(
+        &self,
+        ctxt: &MaybeLivePlaces<'_, '_>,
+        f: &mut std::fmt::Formatter<'_>,
+    ) -> std::fmt::Result {
+        std::fmt::Debug::fmt(&ctxt.checked_places.places[*self], f)
+    }
+}
+
+pub struct MaybeLivePlaces<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    checked_places: &'a PlaceSet<'tcx>,
+    capture_kind: CaptureKind,
+    self_assignment: FxHashSet<Location>,
+}
+
+impl<'tcx> MaybeLivePlaces<'_, 'tcx> {
+    fn transfer_function<'a>(
+        &'a self,
+        trans: &'a mut DenseBitSet<PlaceIndex>,
+    ) -> TransferFunction<'a, 'tcx> {
+        TransferFunction {
+            tcx: self.tcx,
+            checked_places: &self.checked_places,
+            capture_kind: self.capture_kind,
+            trans,
+            self_assignment: &self.self_assignment,
+        }
+    }
+}
+
+impl<'tcx> Analysis<'tcx> for MaybeLivePlaces<'_, 'tcx> {
+    type Domain = DenseBitSet<PlaceIndex>;
+    type Direction = Backward;
+
+    const NAME: &'static str = "liveness-lint";
+
+    fn bottom_value(&self, _: &Body<'tcx>) -> Self::Domain {
+        // bottom = not live
+        DenseBitSet::new_empty(self.checked_places.len())
+    }
+
+    fn initialize_start_block(&self, _: &Body<'tcx>, _: &mut Self::Domain) {
+        // No variables are live until we observe a use
+    }
+
+    fn apply_primary_statement_effect(
+        &mut self,
+        trans: &mut Self::Domain,
+        statement: &Statement<'tcx>,
+        location: Location,
+    ) {
+        self.transfer_function(trans).visit_statement(statement, location);
+    }
+
+    fn apply_primary_terminator_effect<'mir>(
+        &mut self,
+        trans: &mut Self::Domain,
+        terminator: &'mir Terminator<'tcx>,
+        location: Location,
+    ) -> TerminatorEdges<'mir, 'tcx> {
+        self.transfer_function(trans).visit_terminator(terminator, location);
+        terminator.edges()
+    }
+
+    fn apply_call_return_effect(
+        &mut self,
+        _trans: &mut Self::Domain,
+        _block: BasicBlock,
+        _return_places: CallReturnPlaces<'_, 'tcx>,
+    ) {
+        // FIXME: what should happen here?
+    }
+}
+
+struct TransferFunction<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    checked_places: &'a PlaceSet<'tcx>,
+    trans: &'a mut DenseBitSet<PlaceIndex>,
+    capture_kind: CaptureKind,
+    self_assignment: &'a FxHashSet<Location>,
+}
+
+impl<'tcx> Visitor<'tcx> for TransferFunction<'_, 'tcx> {
+    fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
+        match statement.kind {
+            // `ForLet(None)` fake read erroneously marks the just-assigned local as live.
+            // This defeats the purpose of the analysis for `let` bindings.
+            StatementKind::FakeRead(box (FakeReadCause::ForLet(None), _)) => return,
+            // Handle self-assignment by restricting the read/write they do.
+            StatementKind::Assign(box (ref dest, ref rvalue))
+                if self.self_assignment.contains(&location) =>
+            {
+                if let Rvalue::BinaryOp(
+                    BinOp::AddWithOverflow | BinOp::SubWithOverflow | BinOp::MulWithOverflow,
+                    box (_, rhs),
+                ) = rvalue
+                {
+                    // We are computing the binary operation:
+                    // - the LHS will be assigned, so we don't read it;
+                    // - the RHS still needs to be read.
+                    self.visit_operand(rhs, location);
+                    self.visit_place(
+                        dest,
+                        PlaceContext::MutatingUse(MutatingUseContext::Store),
+                        location,
+                    );
+                } else if let Rvalue::BinaryOp(_, box (_, rhs)) = rvalue {
+                    // We are computing the binary operation:
+                    // - the LHS is being updated, so we don't read it;
+                    // - the RHS still needs to be read.
+                    self.visit_operand(rhs, location);
+                } else {
+                    // This is the second part of a checked self-assignment,
+                    // we are assigning the result.
+                    // We do not consider the write to the destination as a `def`.
+                    // `self_assignment` must be false if the assignment is indirect.
+                    self.visit_rvalue(rvalue, location);
+                }
+            }
+            _ => self.super_statement(statement, location),
+        }
+    }
+
+    fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
+        // By-ref captures could be read by the surrounding environment, so we mark
+        // them as live upon yield and return.
+        match terminator.kind {
+            TerminatorKind::Return
+            | TerminatorKind::Yield { .. }
+            | TerminatorKind::Goto { target: START_BLOCK } // Inserted for the `FnMut` case.
+                if self.capture_kind != CaptureKind::None =>
+            {
+                // All indirect captures have an effect on the environment, so we mark them as live.
+                for (index, place) in self.checked_places.iter() {
+                    if place.local == ty::CAPTURE_STRUCT_LOCAL
+                        && place.projection.last() == Some(&PlaceElem::Deref)
+                    {
+                        self.trans.insert(index);
+                    }
+                }
+            }
+            // Do not consider a drop to be a use. We whitelist interesting drops elsewhere.
+            TerminatorKind::Drop { .. } => {}
+            // Ignore assertions since they must be triggered by actual code.
+            TerminatorKind::Assert { .. } => {}
+            _ => self.super_terminator(terminator, location),
+        }
+    }
+
+    fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
+        match rvalue {
+            // When a closure/generator does not use some of its captures, do not consider these
+            // captures as live in the surrounding function. This allows to report unused variables,
+            // even if they have been (uselessly) captured.
+            Rvalue::Aggregate(
+                box AggregateKind::Closure(def_id, _) | box AggregateKind::Coroutine(def_id, _),
+                operands,
+            ) => {
+                if let Some(def_id) = def_id.as_local() {
+                    let dead_captures = self.tcx.check_liveness(def_id);
+                    for (field, operand) in
+                        operands.iter_enumerated().take(dead_captures.domain_size())
+                    {
+                        if !dead_captures.contains(field) {
+                            self.visit_operand(operand, location);
+                        }
+                    }
+                }
+            }
+            _ => self.super_rvalue(rvalue, location),
+        }
+    }
+
+    fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
+        if let Some((index, extra_projections)) = self.checked_places.get(place.as_ref()) {
+            for i in (extra_projections.len()..=place.projection.len()).rev() {
+                let place_part =
+                    PlaceRef { local: place.local, projection: &place.projection[..i] };
+                let extra_projections = &place.projection[i..];
+
+                if let Some(&elem) = extra_projections.get(0) {
+                    self.visit_projection_elem(place_part, elem, context, location);
+                }
+            }
+
+            match DefUse::for_place(extra_projections, context) {
+                Some(DefUse::Def) => {
+                    self.trans.remove(index);
+                }
+                Some(DefUse::Use) => {
+                    self.trans.insert(index);
+                }
+                None => {}
+            }
+        } else {
+            self.super_place(place, context, location)
+        }
+    }
+
+    fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
+        if let Some((index, _proj)) = self.checked_places.get(local.into()) {
+            debug_assert_eq!(_proj, &[]);
+            match DefUse::for_place(&[], context) {
+                Some(DefUse::Def) => {
+                    self.trans.remove(index);
+                }
+                Some(DefUse::Use) => {
+                    self.trans.insert(index);
+                }
+                _ => {}
+            }
+        }
+    }
+}
+
+#[derive(Eq, PartialEq, Debug, Clone)]
+enum DefUse {
+    Def,
+    Use,
+}
+
+fn is_indirect(proj: &[PlaceElem<'_>]) -> bool {
+    proj.iter().any(|p| p.is_indirect())
+}
+
+impl DefUse {
+    fn for_place<'tcx>(projection: &[PlaceElem<'tcx>], context: PlaceContext) -> Option<DefUse> {
+        let is_indirect = is_indirect(projection);
+        match context {
+            PlaceContext::MutatingUse(
+                MutatingUseContext::Store | MutatingUseContext::SetDiscriminant,
+            ) => {
+                if is_indirect {
+                    // Treat derefs as a use of the base local. `*p = 4` is not a def of `p` but a
+                    // use.
+                    Some(DefUse::Use)
+                } else if projection.is_empty() {
+                    Some(DefUse::Def)
+                } else {
+                    None
+                }
+            }
+
+            // For the associated terminators, this is only a `Def` when the terminator returns
+            // "successfully." As such, we handle this case separately in `call_return_effect`
+            // above. However, if the place looks like `*_5`, this is still unconditionally a use of
+            // `_5`.
+            PlaceContext::MutatingUse(
+                MutatingUseContext::Call
+                | MutatingUseContext::Yield
+                | MutatingUseContext::AsmOutput,
+            ) => is_indirect.then_some(DefUse::Use),
+
+            // All other contexts are uses...
+            PlaceContext::MutatingUse(
+                MutatingUseContext::RawBorrow
+                | MutatingUseContext::Borrow
+                | MutatingUseContext::Drop
+                | MutatingUseContext::Retag,
+            )
+            | PlaceContext::NonMutatingUse(
+                NonMutatingUseContext::RawBorrow
+                | NonMutatingUseContext::Copy
+                | NonMutatingUseContext::Inspect
+                | NonMutatingUseContext::Move
+                | NonMutatingUseContext::FakeBorrow
+                | NonMutatingUseContext::SharedBorrow
+                | NonMutatingUseContext::PlaceMention,
+            ) => Some(DefUse::Use),
+
+            PlaceContext::NonUse(
+                NonUseContext::StorageLive
+                | NonUseContext::StorageDead
+                | NonUseContext::AscribeUserTy(_)
+                | NonUseContext::BackwardIncompatibleDropHint
+                | NonUseContext::VarDebugInfo,
+            ) => None,
+
+            PlaceContext::MutatingUse(MutatingUseContext::Projection)
+            | PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection) => {
+                unreachable!("A projection could be a def or a use and must be handled separately")
+            }
+        }
+    }
+}

compiler/rustc_passes/messages.ftl

@@ -395,8 +395,6 @@ passes_macro_only_attribute =
 passes_may_dangle =
     `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
 
-passes_maybe_string_interpolation = you might have meant to use string interpolation in this string literal
-
 passes_missing_const_err =
     attributes `#[rustc_const_unstable]`, `#[rustc_const_stable]` and `#[rustc_const_stable_indirect]` require the function or method to be `const`
     .help = make the function or method const
@@ -568,8 +566,6 @@ passes_should_be_applied_to_trait =
     attribute should be applied to a trait
     .label = not a trait
 
-passes_string_interpolation_only_works = string interpolation only works in `format!` invocations
-
 passes_trait_impl_const_stability_mismatch = const stability on the impl does not match the const stability on the trait
 passes_trait_impl_const_stability_mismatch_impl_stable = this impl is (implicitly) stable...
 passes_trait_impl_const_stability_mismatch_impl_unstable = this impl is unstable...
@@ -619,11 +615,6 @@ passes_unnecessary_partial_stable_feature = the feature `{$feature}` has been pa
 
 passes_unnecessary_stable_feature = the feature `{$feature}` has been stable since {$since} and no longer requires an attribute to enable
 
-passes_unreachable_due_to_uninhabited = unreachable {$descr}
-    .label = unreachable {$descr}
-    .label_orig = any code following this expression is unreachable
-    .note = this expression has type `{$ty}`, which is uninhabited
-
 passes_unrecognized_argument =
     unrecognized argument
 
@@ -641,18 +632,6 @@ passes_unused =
     unused attribute
     .suggestion = remove this attribute
 
-passes_unused_assign = value assigned to `{$name}` is never read
-    .help = maybe it is overwritten before being read?
-
-passes_unused_assign_passed = value passed to `{$name}` is never read
-    .help = maybe it is overwritten before being read?
-
-passes_unused_assign_suggestion =
-    you might have meant to mutate the pointed at value being passed in, instead of changing the reference in the local binding
-
-passes_unused_capture_maybe_capture_ref = value captured by `{$name}` is never read
-    .help = did you mean to capture by reference instead?
-
 passes_unused_default_method_body_const_note =
     `default_method_body_is_const` has been replaced with `const` on traits
 
@@ -676,25 +655,6 @@ passes_unused_multiple =
 passes_unused_no_lints_note =
     attribute `{$name}` without any lints has no effect
 
-passes_unused_var_assigned_only = variable `{$name}` is assigned to, but never used
-    .note = consider using `_{$name}` instead
-
-passes_unused_var_maybe_capture_ref = unused variable: `{$name}`
-    .help = did you mean to capture by reference instead?
-
-passes_unused_var_remove_field = unused variable: `{$name}`
-passes_unused_var_remove_field_suggestion = try removing the field
-passes_unused_var_typo = you might have meant to pattern match on the similarly named {$kind} `{$item_name}`
-
-passes_unused_variable_args_in_macro = `{$name}` is captured in macro and introduced a unused variable
-
-passes_unused_variable_try_ignore = unused variable: `{$name}`
-    .suggestion = try ignoring the field
-
-passes_unused_variable_try_prefix = unused variable: `{$name}`
-    .label = unused variable
-    .suggestion = if this is intentional, prefix it with an underscore
-
 passes_useless_assignment =
     useless assignment of {$is_field_assign ->
         [true] field

compiler/rustc_passes/src/errors.rs

@@ -4,7 +4,7 @@
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, DiagSymbolList, Diagnostic, EmissionGuarantee, Level,
-    MultiSpan, Subdiagnostic,
+    MultiSpan,
 };
 use rustc_hir::Target;
 use rustc_hir::attrs::{MirDialect, MirPhase};
@@ -1308,73 +1308,6 @@ pub(crate) struct ProcMacroBadSig {
     pub kind: ProcMacroKind,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(passes_unreachable_due_to_uninhabited)]
-pub(crate) struct UnreachableDueToUninhabited<'desc, 'tcx> {
-    pub descr: &'desc str,
-    #[label]
-    pub expr: Span,
-    #[label(passes_label_orig)]
-    #[note]
-    pub orig: Span,
-    pub ty: Ty<'tcx>,
-}
-
-#[derive(LintDiagnostic)]
-#[diag(passes_unused_var_maybe_capture_ref)]
-#[help]
-pub(crate) struct UnusedVarMaybeCaptureRef {
-    pub name: String,
-}
-
-#[derive(LintDiagnostic)]
-#[diag(passes_unused_capture_maybe_capture_ref)]
-#[help]
-pub(crate) struct UnusedCaptureMaybeCaptureRef {
-    pub name: String,
-}
-
-#[derive(LintDiagnostic)]
-#[diag(passes_unused_var_remove_field)]
-pub(crate) struct UnusedVarRemoveField {
-    pub name: String,
-    #[subdiagnostic]
-    pub sugg: UnusedVarRemoveFieldSugg,
-}
-
-#[derive(Subdiagnostic)]
-#[multipart_suggestion(
-    passes_unused_var_remove_field_suggestion,
-    applicability = "machine-applicable"
-)]
-pub(crate) struct UnusedVarRemoveFieldSugg {
-    #[suggestion_part(code = "")]
-    pub spans: Vec<Span>,
-}
-
-#[derive(LintDiagnostic)]
-#[diag(passes_unused_var_assigned_only)]
-#[note]
-pub(crate) struct UnusedVarAssignedOnly {
-    pub name: String,
-    #[subdiagnostic]
-    pub typo: Option<PatternTypo>,
-}
-
-#[derive(Subdiagnostic)]
-#[multipart_suggestion(
-    passes_unused_var_typo,
-    style = "verbose",
-    applicability = "maybe-incorrect"
-)]
-pub(crate) struct PatternTypo {
-    #[suggestion_part(code = "{code}")]
-    pub span: Span,
-    pub code: String,
-    pub item_name: String,
-    pub kind: String,
-}
-
 #[derive(LintDiagnostic)]
 #[diag(passes_unnecessary_stable_feature)]
 pub(crate) struct UnnecessaryStableFeature {
@@ -1399,102 +1332,6 @@ pub(crate) struct UnnecessaryPartialStableFeature {
 #[note]
 pub(crate) struct IneffectiveUnstableImpl;
 
-#[derive(LintDiagnostic)]
-#[diag(passes_unused_assign)]
-pub(crate) struct UnusedAssign {
-    pub name: String,
-    #[subdiagnostic]
-    pub suggestion: Option<UnusedAssignSuggestion>,
-    #[help]
-    pub help: bool,
-}
-
-#[derive(Subdiagnostic)]
-#[multipart_suggestion(passes_unused_assign_suggestion, applicability = "maybe-incorrect")]
-pub(crate) struct UnusedAssignSuggestion {
-    pub pre: &'static str,
-    #[suggestion_part(code = "{pre}mut ")]
-    pub ty_span: Option<Span>,
-    #[suggestion_part(code = "")]
-    pub ty_ref_span: Span,
-    #[suggestion_part(code = "*")]
-    pub ident_span: Span,
-    #[suggestion_part(code = "")]
-    pub expr_ref_span: Span,
-}
-
-#[derive(LintDiagnostic)]
-#[diag(passes_unused_assign_passed)]
-#[help]
-pub(crate) struct UnusedAssignPassed {
-    pub name: String,
-}
-
-#[derive(LintDiagnostic)]
-#[diag(passes_unused_variable_try_prefix)]
-pub(crate) struct UnusedVariableTryPrefix {
-    #[label]
-    pub label: Option<Span>,
-    #[subdiagnostic]
-    pub string_interp: Vec<UnusedVariableStringInterp>,
-    #[subdiagnostic]
-    pub sugg: UnusedVariableSugg,
-    pub name: String,
-    #[subdiagnostic]
-    pub typo: Option<PatternTypo>,
-}
-
-#[derive(Subdiagnostic)]
-pub(crate) enum UnusedVariableSugg {
-    #[multipart_suggestion(passes_suggestion, applicability = "maybe-incorrect")]
-    TryPrefixSugg {
-        #[suggestion_part(code = "_{name}")]
-        spans: Vec<Span>,
-        name: String,
-    },
-    #[help(passes_unused_variable_args_in_macro)]
-    NoSugg {
-        #[primary_span]
-        span: Span,
-        name: String,
-    },
-}
-
-pub(crate) struct UnusedVariableStringInterp {
-    pub lit: Span,
-    pub lo: Span,
-    pub hi: Span,
-}
-
-impl Subdiagnostic for UnusedVariableStringInterp {
-    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        diag.span_label(self.lit, crate::fluent_generated::passes_maybe_string_interpolation);
-        diag.multipart_suggestion(
-            crate::fluent_generated::passes_string_interpolation_only_works,
-            vec![(self.lo, String::from("format!(")), (self.hi, String::from(")"))],
-            Applicability::MachineApplicable,
-        );
-    }
-}
-
-#[derive(LintDiagnostic)]
-#[diag(passes_unused_variable_try_ignore)]
-pub(crate) struct UnusedVarTryIgnore {
-    pub name: String,
-    #[subdiagnostic]
-    pub sugg: UnusedVarTryIgnoreSugg,
-}
-
-#[derive(Subdiagnostic)]
-#[multipart_suggestion(passes_suggestion, applicability = "maybe-incorrect")]
-pub(crate) struct UnusedVarTryIgnoreSugg {
-    #[suggestion_part(code = "{name}: _")]
-    pub shorthands: Vec<Span>,
-    #[suggestion_part(code = "_")]
-    pub non_shorthands: Vec<Span>,
-    pub name: String,
-}
-
 #[derive(LintDiagnostic)]
 #[diag(passes_attr_crate_level)]
 #[note]

compiler/rustc_passes/src/lib.rs

@@ -23,13 +23,11 @@
 mod diagnostic_items;
 pub mod entry;
 mod errors;
-#[cfg(debug_assertions)]
 pub mod hir_id_validator;
 pub mod input_stats;
 mod lang_items;
 pub mod layout_test;
 mod lib_features;
-mod liveness;
 mod reachable;
 pub mod stability;
 mod upvars;
@@ -45,7 +43,6 @@ pub fn provide(providers: &mut Providers) {
     entry::provide(providers);
     lang_items::provide(providers);
     lib_features::provide(providers);
-    liveness::provide(providers);
     reachable::provide(providers);
     stability::provide(providers);
     upvars::provide(providers);

compiler/rustc_passes/src/liveness.rs

@@ -1,1898 +0,0 @@
-//! A classic liveness analysis based on dataflow over the AST. Computes,
-//! for each local variable in a function, whether that variable is live
-//! at a given point. Program execution points are identified by their
-//! IDs.
-//!
-//! # Basic idea
-//!
-//! The basic model is that each local variable is assigned an index. We
-//! represent sets of local variables using a vector indexed by this
-//! index. The value in the vector is either 0, indicating the variable
-//! is dead, or the ID of an expression that uses the variable.
-//!
-//! We conceptually walk over the AST in reverse execution order. If we
-//! find a use of a variable, we add it to the set of live variables. If
-//! we find an assignment to a variable, we remove it from the set of live
-//! variables. When we have to merge two flows, we take the union of
-//! those two flows -- if the variable is live on both paths, we simply
-//! pick one ID. In the event of loops, we continue doing this until a
-//! fixed point is reached.
-//!
-//! ## Checking initialization
-//!
-//! At the function entry point, all variables must be dead. If this is
-//! not the case, we can report an error using the ID found in the set of
-//! live variables, which identifies a use of the variable which is not
-//! dominated by an assignment.
-//!
-//! ## Checking moves
-//!
-//! After each explicit move, the variable must be dead.
-//!
-//! ## Computing last uses
-//!
-//! Any use of the variable where the variable is dead afterwards is a
-//! last use.
-//!
-//! # Implementation details
-//!
-//! The actual implementation contains two (nested) walks over the AST.
-//! The outer walk has the job of building up the ir_maps instance for the
-//! enclosing function. On the way down the tree, it identifies those AST
-//! nodes and variable IDs that will be needed for the liveness analysis
-//! and assigns them contiguous IDs. The liveness ID for an AST node is
-//! called a `live_node` (it's a newtype'd `u32`) and the ID for a variable
-//! is called a `variable` (another newtype'd `u32`).
-//!
-//! On the way back up the tree, as we are about to exit from a function
-//! declaration we allocate a `liveness` instance. Now that we know
-//! precisely how many nodes and variables we need, we can allocate all
-//! the various arrays that we will need to precisely the right size. We then
-//! perform the actual propagation on the `liveness` instance.
-//!
-//! This propagation is encoded in the various `propagate_through_*()`
-//! methods. It effectively does a reverse walk of the AST; whenever we
-//! reach a loop node, we iterate until a fixed point is reached.
-//!
-//! ## The `RWU` struct
-//!
-//! At each live node `N`, we track three pieces of information for each
-//! variable `V` (these are encapsulated in the `RWU` struct):
-//!
-//! - `reader`: the `LiveNode` ID of some node which will read the value
-//!    that `V` holds on entry to `N`. Formally: a node `M` such
-//!    that there exists a path `P` from `N` to `M` where `P` does not
-//!    write `V`. If the `reader` is `None`, then the current
-//!    value will never be read (the variable is dead, essentially).
-//!
-//! - `writer`: the `LiveNode` ID of some node which will write the
-//!    variable `V` and which is reachable from `N`. Formally: a node `M`
-//!    such that there exists a path `P` from `N` to `M` and `M` writes
-//!    `V`. If the `writer` is `None`, then there is no writer
-//!    of `V` that follows `N`.
-//!
-//! - `used`: a boolean value indicating whether `V` is *used*. We
-//!   distinguish a *read* from a *use* in that a *use* is some read that
-//!   is not just used to generate a new value. For example, `x += 1` is
-//!   a read but not a use. This is used to generate better warnings.
-//!
-//! ## Special nodes and variables
-//!
-//! We generate various special nodes for various, well, special purposes.
-//! These are described in the `Liveness` struct.
-
-use std::io;
-use std::io::prelude::*;
-use std::rc::Rc;
-
-use rustc_data_structures::fx::FxIndexMap;
-use rustc_hir as hir;
-use rustc_hir::attrs::AttributeKind;
-use rustc_hir::def::*;
-use rustc_hir::def_id::LocalDefId;
-use rustc_hir::intravisit::{self, Visitor};
-use rustc_hir::{Expr, HirId, HirIdMap, HirIdSet, find_attr};
-use rustc_index::IndexVec;
-use rustc_middle::query::Providers;
-use rustc_middle::span_bug;
-use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::{self, RootVariableMinCaptureList, Ty, TyCtxt};
-use rustc_session::lint;
-use rustc_span::edit_distance::find_best_match_for_name;
-use rustc_span::{BytePos, Span, Symbol};
-use tracing::{debug, instrument};
-
-use self::LiveNodeKind::*;
-use self::VarKind::*;
-use crate::errors;
-
-mod rwu_table;
-
-rustc_index::newtype_index! {
-    #[debug_format = "v({})"]
-    pub struct Variable {}
-}
-
-rustc_index::newtype_index! {
-    #[debug_format = "ln({})"]
-    pub struct LiveNode {}
-}
-
-#[derive(Copy, Clone, PartialEq, Debug)]
-enum LiveNodeKind {
-    UpvarNode(Span),
-    ExprNode(Span, HirId),
-    VarDefNode(Span, HirId),
-    ClosureNode,
-    ExitNode,
-}
-
-fn live_node_kind_to_string(lnk: LiveNodeKind, tcx: TyCtxt<'_>) -> String {
-    let sm = tcx.sess.source_map();
-    match lnk {
-        UpvarNode(s) => format!("Upvar node [{}]", sm.span_to_diagnostic_string(s)),
-        ExprNode(s, _) => format!("Expr node [{}]", sm.span_to_diagnostic_string(s)),
-        VarDefNode(s, _) => format!("Var def node [{}]", sm.span_to_diagnostic_string(s)),
-        ClosureNode => "Closure node".to_owned(),
-        ExitNode => "Exit node".to_owned(),
-    }
-}
-
-fn check_liveness(tcx: TyCtxt<'_>, def_id: LocalDefId) {
-    // Don't run unused pass for #[derive()]
-    let parent = tcx.local_parent(def_id);
-    if let DefKind::Impl { .. } = tcx.def_kind(parent)
-        && find_attr!(tcx.get_all_attrs(parent), AttributeKind::AutomaticallyDerived(..))
-    {
-        return;
-    }
-
-    // Don't run unused pass for #[naked]
-    if find_attr!(tcx.get_all_attrs(def_id.to_def_id()), AttributeKind::Naked(..)) {
-        return;
-    }
-
-    let mut maps = IrMaps::new(tcx);
-    let body = tcx.hir_body_owned_by(def_id);
-    let hir_id = tcx.hir_body_owner(body.id());
-
-    if let Some(upvars) = tcx.upvars_mentioned(def_id) {
-        for &var_hir_id in upvars.keys() {
-            let var_name = tcx.hir_name(var_hir_id);
-            maps.add_variable(Upvar(var_hir_id, var_name));
-        }
-    }
-
-    // gather up the various local variables, significant expressions,
-    // and so forth:
-    maps.visit_body(&body);
-
-    // compute liveness
-    let mut lsets = Liveness::new(&mut maps, def_id);
-    let entry_ln = lsets.compute(&body, hir_id);
-    lsets.log_liveness(entry_ln, body.id().hir_id);
-
-    // check for various error conditions
-    lsets.visit_body(&body);
-    lsets.warn_about_unused_upvars(entry_ln);
-    lsets.warn_about_unused_args(&body, entry_ln);
-}
-
-pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { check_liveness, ..*providers };
-}
-
-// ______________________________________________________________________
-// Creating ir_maps
-//
-// This is the first pass and the one that drives the main
-// computation. It walks up and down the IR once. On the way down,
-// we count for each function the number of variables as well as
-// liveness nodes. A liveness node is basically an expression or
-// capture clause that does something of interest: either it has
-// interesting control flow or it uses/defines a local variable.
-//
-// On the way back up, at each function node we create liveness sets
-// (we now know precisely how big to make our various vectors and so
-// forth) and then do the data-flow propagation to compute the set
-// of live variables at each program point.
-//
-// Finally, we run back over the IR one last time and, using the
-// computed liveness, check various safety conditions. For example,
-// there must be no live nodes at the definition site for a variable
-// unless it has an initializer. Similarly, each non-mutable local
-// variable must not be assigned if there is some successor
-// assignment. And so forth.
-
-struct CaptureInfo {
-    ln: LiveNode,
-    var_hid: HirId,
-}
-
-#[derive(Copy, Clone, Debug)]
-struct LocalInfo {
-    id: HirId,
-    name: Symbol,
-    is_shorthand: bool,
-}
-
-#[derive(Copy, Clone, Debug)]
-enum VarKind {
-    Param(HirId, Symbol),
-    Local(LocalInfo),
-    Upvar(HirId, Symbol),
-}
-
-struct CollectLitsVisitor<'tcx> {
-    lit_exprs: Vec<&'tcx hir::Expr<'tcx>>,
-}
-
-impl<'tcx> Visitor<'tcx> for CollectLitsVisitor<'tcx> {
-    fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
-        if let hir::ExprKind::Lit(_) = expr.kind {
-            self.lit_exprs.push(expr);
-        }
-        intravisit::walk_expr(self, expr);
-    }
-}
-
-struct IrMaps<'tcx> {
-    tcx: TyCtxt<'tcx>,
-    live_node_map: HirIdMap<LiveNode>,
-    variable_map: HirIdMap<Variable>,
-    capture_info_map: HirIdMap<Rc<Vec<CaptureInfo>>>,
-    var_kinds: IndexVec<Variable, VarKind>,
-    lnks: IndexVec<LiveNode, LiveNodeKind>,
-}
-
-impl<'tcx> IrMaps<'tcx> {
-    fn new(tcx: TyCtxt<'tcx>) -> IrMaps<'tcx> {
-        IrMaps {
-            tcx,
-            live_node_map: HirIdMap::default(),
-            variable_map: HirIdMap::default(),
-            capture_info_map: Default::default(),
-            var_kinds: IndexVec::new(),
-            lnks: IndexVec::new(),
-        }
-    }
-
-    fn add_live_node(&mut self, lnk: LiveNodeKind) -> LiveNode {
-        let ln = self.lnks.push(lnk);
-
-        debug!("{:?} is of kind {}", ln, live_node_kind_to_string(lnk, self.tcx));
-
-        ln
-    }
-
-    fn add_live_node_for_node(&mut self, hir_id: HirId, lnk: LiveNodeKind) {
-        let ln = self.add_live_node(lnk);
-        self.live_node_map.insert(hir_id, ln);
-
-        debug!("{:?} is node {:?}", ln, hir_id);
-    }
-
-    fn add_variable(&mut self, vk: VarKind) -> Variable {
-        let v = self.var_kinds.push(vk);
-
-        match vk {
-            Local(LocalInfo { id: node_id, .. }) | Param(node_id, _) | Upvar(node_id, _) => {
-                self.variable_map.insert(node_id, v);
-            }
-        }
-
-        debug!("{:?} is {:?}", v, vk);
-
-        v
-    }
-
-    fn variable(&self, hir_id: HirId, span: Span) -> Variable {
-        match self.variable_map.get(&hir_id) {
-            Some(&var) => var,
-            None => {
-                span_bug!(span, "no variable registered for id {:?}", hir_id);
-            }
-        }
-    }
-
-    fn variable_name(&self, var: Variable) -> Symbol {
-        match self.var_kinds[var] {
-            Local(LocalInfo { name, .. }) | Param(_, name) | Upvar(_, name) => name,
-        }
-    }
-
-    fn variable_is_shorthand(&self, var: Variable) -> bool {
-        match self.var_kinds[var] {
-            Local(LocalInfo { is_shorthand, .. }) => is_shorthand,
-            Param(..) | Upvar(..) => false,
-        }
-    }
-
-    fn set_captures(&mut self, hir_id: HirId, cs: Vec<CaptureInfo>) {
-        self.capture_info_map.insert(hir_id, Rc::new(cs));
-    }
-
-    fn collect_shorthand_field_ids(&self, pat: &hir::Pat<'tcx>) -> HirIdSet {
-        // For struct patterns, take note of which fields used shorthand
-        // (`x` rather than `x: x`).
-        let mut shorthand_field_ids = HirIdSet::default();
-
-        pat.walk_always(|pat| {
-            if let hir::PatKind::Struct(_, fields, _) = pat.kind {
-                let short = fields.iter().filter(|f| f.is_shorthand);
-                shorthand_field_ids.extend(short.map(|f| f.pat.hir_id));
-            }
-        });
-
-        shorthand_field_ids
-    }
-
-    fn add_from_pat(&mut self, pat: &hir::Pat<'tcx>) {
-        let shorthand_field_ids = self.collect_shorthand_field_ids(pat);
-
-        pat.each_binding(|_, hir_id, _, ident| {
-            self.add_live_node_for_node(hir_id, VarDefNode(ident.span, hir_id));
-            self.add_variable(Local(LocalInfo {
-                id: hir_id,
-                name: ident.name,
-                is_shorthand: shorthand_field_ids.contains(&hir_id),
-            }));
-        });
-    }
-}
-
-impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
-    fn visit_local(&mut self, local: &'tcx hir::LetStmt<'tcx>) {
-        self.add_from_pat(local.pat);
-        if local.els.is_some() {
-            self.add_live_node_for_node(local.hir_id, ExprNode(local.span, local.hir_id));
-        }
-        intravisit::walk_local(self, local);
-    }
-
-    fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) {
-        self.add_from_pat(&arm.pat);
-        intravisit::walk_arm(self, arm);
-    }
-
-    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
-        let shorthand_field_ids = self.collect_shorthand_field_ids(param.pat);
-        param.pat.each_binding(|_bm, hir_id, _x, ident| {
-            let var = match param.pat.kind {
-                rustc_hir::PatKind::Struct(..) => Local(LocalInfo {
-                    id: hir_id,
-                    name: ident.name,
-                    is_shorthand: shorthand_field_ids.contains(&hir_id),
-                }),
-                _ => Param(hir_id, ident.name),
-            };
-            self.add_variable(var);
-        });
-        intravisit::walk_param(self, param);
-    }
-
-    fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
-        match expr.kind {
-            // live nodes required for uses or definitions of variables:
-            hir::ExprKind::Path(hir::QPath::Resolved(_, path)) => {
-                debug!("expr {}: path that leads to {:?}", expr.hir_id, path.res);
-                if let Res::Local(_var_hir_id) = path.res {
-                    self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id));
-                }
-            }
-            hir::ExprKind::Closure(closure) => {
-                // Interesting control flow (for loops can contain labeled
-                // breaks or continues)
-                self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id));
-
-                // Make a live_node for each mentioned variable, with the span
-                // being the location that the variable is used. This results
-                // in better error messages than just pointing at the closure
-                // construction site.
-                let mut call_caps = Vec::new();
-                if let Some(upvars) = self.tcx.upvars_mentioned(closure.def_id) {
-                    call_caps.extend(upvars.keys().map(|var_id| {
-                        let upvar = upvars[var_id];
-                        let upvar_ln = self.add_live_node(UpvarNode(upvar.span));
-                        CaptureInfo { ln: upvar_ln, var_hid: *var_id }
-                    }));
-                }
-                self.set_captures(expr.hir_id, call_caps);
-            }
-
-            hir::ExprKind::Let(let_expr) => {
-                self.add_from_pat(let_expr.pat);
-            }
-
-            // live nodes required for interesting control flow:
-            hir::ExprKind::If(..)
-            | hir::ExprKind::Match(..)
-            | hir::ExprKind::Loop(..)
-            | hir::ExprKind::Yield(..) => {
-                self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id));
-            }
-            hir::ExprKind::Binary(op, ..) if op.node.is_lazy() => {
-                self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id));
-            }
-
-            // Inline assembly may contain labels.
-            hir::ExprKind::InlineAsm(asm) if asm.contains_label() => {
-                self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id));
-                intravisit::walk_expr(self, expr);
-            }
-
-            // otherwise, live nodes are not required:
-            hir::ExprKind::Index(..)
-            | hir::ExprKind::Field(..)
-            | hir::ExprKind::Array(..)
-            | hir::ExprKind::Call(..)
-            | hir::ExprKind::MethodCall(..)
-            | hir::ExprKind::Use(..)
-            | hir::ExprKind::Tup(..)
-            | hir::ExprKind::Binary(..)
-            | hir::ExprKind::AddrOf(..)
-            | hir::ExprKind::Cast(..)
-            | hir::ExprKind::DropTemps(..)
-            | hir::ExprKind::Unary(..)
-            | hir::ExprKind::Break(..)
-            | hir::ExprKind::Continue(_)
-            | hir::ExprKind::Lit(_)
-            | hir::ExprKind::ConstBlock(..)
-            | hir::ExprKind::Ret(..)
-            | hir::ExprKind::Become(..)
-            | hir::ExprKind::Block(..)
-            | hir::ExprKind::Assign(..)
-            | hir::ExprKind::AssignOp(..)
-            | hir::ExprKind::Struct(..)
-            | hir::ExprKind::Repeat(..)
-            | hir::ExprKind::InlineAsm(..)
-            | hir::ExprKind::OffsetOf(..)
-            | hir::ExprKind::Type(..)
-            | hir::ExprKind::UnsafeBinderCast(..)
-            | hir::ExprKind::Err(_)
-            | hir::ExprKind::Path(hir::QPath::TypeRelative(..))
-            | hir::ExprKind::Path(hir::QPath::LangItem(..)) => {}
-        }
-        intravisit::walk_expr(self, expr);
-    }
-}
-
-// ______________________________________________________________________
-// Computing liveness sets
-//
-// Actually we compute just a bit more than just liveness, but we use
-// the same basic propagation framework in all cases.
-
-const ACC_READ: u32 = 1;
-const ACC_WRITE: u32 = 2;
-const ACC_USE: u32 = 4;
-
-struct Liveness<'a, 'tcx> {
-    ir: &'a mut IrMaps<'tcx>,
-    typeck_results: &'a ty::TypeckResults<'tcx>,
-    typing_env: ty::TypingEnv<'tcx>,
-    closure_min_captures: Option<&'tcx RootVariableMinCaptureList<'tcx>>,
-    successors: IndexVec<LiveNode, Option<LiveNode>>,
-    rwu_table: rwu_table::RWUTable,
-
-    /// A live node representing a point of execution before closure entry &
-    /// after closure exit. Used to calculate liveness of captured variables
-    /// through calls to the same closure. Used for Fn & FnMut closures only.
-    closure_ln: LiveNode,
-    /// A live node representing every 'exit' from the function, whether it be
-    /// by explicit return, panic, or other means.
-    exit_ln: LiveNode,
-
-    // mappings from loop node ID to LiveNode
-    // ("break" label should map to loop node ID,
-    // it probably doesn't now)
-    break_ln: HirIdMap<LiveNode>,
-    cont_ln: HirIdMap<LiveNode>,
-}
-
-impl<'a, 'tcx> Liveness<'a, 'tcx> {
-    fn new(ir: &'a mut IrMaps<'tcx>, body_owner: LocalDefId) -> Liveness<'a, 'tcx> {
-        let typeck_results = ir.tcx.typeck(body_owner);
-        // Liveness linting runs after building the THIR. We make several assumptions based on
-        // typeck succeeding, e.g. that breaks and continues are well-formed.
-        assert!(typeck_results.tainted_by_errors.is_none());
-        // FIXME(#132279): we're in a body here.
-        let typing_env = ty::TypingEnv::non_body_analysis(ir.tcx, body_owner);
-        let closure_min_captures = typeck_results.closure_min_captures.get(&body_owner);
-        let closure_ln = ir.add_live_node(ClosureNode);
-        let exit_ln = ir.add_live_node(ExitNode);
-
-        let num_live_nodes = ir.lnks.len();
-        let num_vars = ir.var_kinds.len();
-
-        Liveness {
-            ir,
-            typeck_results,
-            typing_env,
-            closure_min_captures,
-            successors: IndexVec::from_elem_n(None, num_live_nodes),
-            rwu_table: rwu_table::RWUTable::new(num_live_nodes, num_vars),
-            closure_ln,
-            exit_ln,
-            break_ln: Default::default(),
-            cont_ln: Default::default(),
-        }
-    }
-
-    fn live_node(&self, hir_id: HirId, span: Span) -> LiveNode {
-        match self.ir.live_node_map.get(&hir_id) {
-            Some(&ln) => ln,
-            None => {
-                // This must be a mismatch between the ir_map construction
-                // above and the propagation code below; the two sets of
-                // code have to agree about which AST nodes are worth
-                // creating liveness nodes for.
-                span_bug!(span, "no live node registered for node {:?}", hir_id);
-            }
-        }
-    }
-
-    fn variable(&self, hir_id: HirId, span: Span) -> Variable {
-        self.ir.variable(hir_id, span)
-    }
-
-    fn define_bindings_in_pat(&mut self, pat: &hir::Pat<'_>, mut succ: LiveNode) -> LiveNode {
-        // In an or-pattern, only consider the first non-never pattern; any later patterns
-        // must have the same bindings, and we also consider that pattern
-        // to be the "authoritative" set of ids.
-        pat.each_binding_or_first(&mut |_, hir_id, pat_sp, ident| {
-            let ln = self.live_node(hir_id, pat_sp);
-            let var = self.variable(hir_id, ident.span);
-            self.init_from_succ(ln, succ);
-            self.define(ln, var);
-            succ = ln;
-        });
-        succ
-    }
-
-    fn live_on_entry(&self, ln: LiveNode, var: Variable) -> bool {
-        self.rwu_table.get_reader(ln, var)
-    }
-
-    // Is this variable live on entry to any of its successor nodes?
-    fn live_on_exit(&self, ln: LiveNode, var: Variable) -> bool {
-        let successor = self.successors[ln].unwrap();
-        self.live_on_entry(successor, var)
-    }
-
-    fn used_on_entry(&self, ln: LiveNode, var: Variable) -> bool {
-        self.rwu_table.get_used(ln, var)
-    }
-
-    fn assigned_on_entry(&self, ln: LiveNode, var: Variable) -> bool {
-        self.rwu_table.get_writer(ln, var)
-    }
-
-    fn assigned_on_exit(&self, ln: LiveNode, var: Variable) -> bool {
-        match self.successors[ln] {
-            Some(successor) => self.assigned_on_entry(successor, var),
-            None => {
-                self.ir.tcx.dcx().delayed_bug("no successor");
-                true
-            }
-        }
-    }
-
-    fn write_vars<F>(&self, wr: &mut dyn Write, mut test: F) -> io::Result<()>
-    where
-        F: FnMut(Variable) -> bool,
-    {
-        for var in self.ir.var_kinds.indices() {
-            if test(var) {
-                write!(wr, " {var:?}")?;
-            }
-        }
-        Ok(())
-    }
-
-    #[allow(unused_must_use)]
-    fn ln_str(&self, ln: LiveNode) -> String {
-        let mut wr = Vec::new();
-        {
-            let wr = &mut wr as &mut dyn Write;
-            write!(wr, "[{:?} of kind {:?} reads", ln, self.ir.lnks[ln]);
-            self.write_vars(wr, |var| self.rwu_table.get_reader(ln, var));
-            write!(wr, "  writes");
-            self.write_vars(wr, |var| self.rwu_table.get_writer(ln, var));
-            write!(wr, "  uses");
-            self.write_vars(wr, |var| self.rwu_table.get_used(ln, var));
-
-            write!(wr, "  precedes {:?}]", self.successors[ln]);
-        }
-        String::from_utf8(wr).unwrap()
-    }
-
-    fn log_liveness(&self, entry_ln: LiveNode, hir_id: HirId) {
-        // hack to skip the loop unless debug! is enabled:
-        debug!(
-            "^^ liveness computation results for body {} (entry={:?})",
-            {
-                for ln_idx in self.ir.lnks.indices() {
-                    debug!("{:?}", self.ln_str(ln_idx));
-                }
-                hir_id
-            },
-            entry_ln
-        );
-    }
-
-    fn init_empty(&mut self, ln: LiveNode, succ_ln: LiveNode) {
-        self.successors[ln] = Some(succ_ln);
-
-        // It is not necessary to initialize the RWUs here because they are all
-        // empty when created, and the sets only grow during iterations.
-    }
-
-    fn init_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode) {
-        // more efficient version of init_empty() / merge_from_succ()
-        self.successors[ln] = Some(succ_ln);
-        self.rwu_table.copy(ln, succ_ln);
-        debug!("init_from_succ(ln={}, succ={})", self.ln_str(ln), self.ln_str(succ_ln));
-    }
-
-    fn merge_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode) -> bool {
-        if ln == succ_ln {
-            return false;
-        }
-
-        let changed = self.rwu_table.union(ln, succ_ln);
-        debug!("merge_from_succ(ln={:?}, succ={}, changed={})", ln, self.ln_str(succ_ln), changed);
-        changed
-    }
-
-    // Indicates that a local variable was *defined*; we know that no
-    // uses of the variable can precede the definition (resolve checks
-    // this) so we just clear out all the data.
-    fn define(&mut self, writer: LiveNode, var: Variable) {
-        let used = self.rwu_table.get_used(writer, var);
-        self.rwu_table.set(writer, var, rwu_table::RWU { reader: false, writer: false, used });
-        debug!("{:?} defines {:?}: {}", writer, var, self.ln_str(writer));
-    }
-
-    // Either read, write, or both depending on the acc bitset
-    fn acc(&mut self, ln: LiveNode, var: Variable, acc: u32) {
-        debug!("{:?} accesses[{:x}] {:?}: {}", ln, acc, var, self.ln_str(ln));
-
-        let mut rwu = self.rwu_table.get(ln, var);
-
-        if (acc & ACC_WRITE) != 0 {
-            rwu.reader = false;
-            rwu.writer = true;
-        }
-
-        // Important: if we both read/write, must do read second
-        // or else the write will override.
-        if (acc & ACC_READ) != 0 {
-            rwu.reader = true;
-        }
-
-        if (acc & ACC_USE) != 0 {
-            rwu.used = true;
-        }
-
-        self.rwu_table.set(ln, var, rwu);
-    }
-
-    fn compute(&mut self, body: &hir::Body<'_>, hir_id: HirId) -> LiveNode {
-        debug!("compute: for body {:?}", body.id().hir_id);
-
-        // # Liveness of captured variables
-        //
-        // When computing the liveness for captured variables we take into
-        // account how variable is captured (ByRef vs ByValue) and what is the
-        // closure kind (Coroutine / FnOnce vs Fn / FnMut).
-        //
-        // Variables captured by reference are assumed to be used on the exit
-        // from the closure.
-        //
-        // In FnOnce closures, variables captured by value are known to be dead
-        // on exit since it is impossible to call the closure again.
-        //
-        // In Fn / FnMut closures, variables captured by value are live on exit
-        // if they are live on the entry to the closure, since only the closure
-        // itself can access them on subsequent calls.
-
-        if let Some(closure_min_captures) = self.closure_min_captures {
-            // Mark upvars captured by reference as used after closure exits.
-            for (&var_hir_id, min_capture_list) in closure_min_captures {
-                for captured_place in min_capture_list {
-                    match captured_place.info.capture_kind {
-                        ty::UpvarCapture::ByRef(_) => {
-                            let var = self.variable(
-                                var_hir_id,
-                                captured_place.get_capture_kind_span(self.ir.tcx),
-                            );
-                            self.acc(self.exit_ln, var, ACC_READ | ACC_USE);
-                        }
-                        ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => {}
-                    }
-                }
-            }
-        }
-
-        let succ = self.propagate_through_expr(body.value, self.exit_ln);
-
-        if self.closure_min_captures.is_none() {
-            // Either not a closure, or closure without any captured variables.
-            // No need to determine liveness of captured variables, since there
-            // are none.
-            return succ;
-        }
-
-        let ty = self.typeck_results.node_type(hir_id);
-        match ty.kind() {
-            ty::Closure(_def_id, args) => match args.as_closure().kind() {
-                ty::ClosureKind::Fn => {}
-                ty::ClosureKind::FnMut => {}
-                ty::ClosureKind::FnOnce => return succ,
-            },
-            ty::CoroutineClosure(_def_id, args) => match args.as_coroutine_closure().kind() {
-                ty::ClosureKind::Fn => {}
-                ty::ClosureKind::FnMut => {}
-                ty::ClosureKind::FnOnce => return succ,
-            },
-            ty::Coroutine(..) => return succ,
-            _ => {
-                span_bug!(
-                    body.value.span,
-                    "{} has upvars so it should have a closure type: {:?}",
-                    hir_id,
-                    ty
-                );
-            }
-        };
-
-        // Propagate through calls to the closure.
-        loop {
-            self.init_from_succ(self.closure_ln, succ);
-            for param in body.params {
-                param.pat.each_binding(|_bm, hir_id, _x, ident| {
-                    let var = self.variable(hir_id, ident.span);
-                    self.define(self.closure_ln, var);
-                })
-            }
-
-            if !self.merge_from_succ(self.exit_ln, self.closure_ln) {
-                break;
-            }
-            assert_eq!(succ, self.propagate_through_expr(body.value, self.exit_ln));
-        }
-
-        succ
-    }
-
-    fn propagate_through_block(&mut self, blk: &hir::Block<'_>, succ: LiveNode) -> LiveNode {
-        if blk.targeted_by_break {
-            self.break_ln.insert(blk.hir_id, succ);
-        }
-        let succ = self.propagate_through_opt_expr(blk.expr, succ);
-        blk.stmts.iter().rev().fold(succ, |succ, stmt| self.propagate_through_stmt(stmt, succ))
-    }
-
-    fn propagate_through_stmt(&mut self, stmt: &hir::Stmt<'_>, succ: LiveNode) -> LiveNode {
-        match stmt.kind {
-            hir::StmtKind::Let(local) => {
-                // Note: we mark the variable as defined regardless of whether
-                // there is an initializer. Initially I had thought to only mark
-                // the live variable as defined if it was initialized, and then we
-                // could check for uninit variables just by scanning what is live
-                // at the start of the function. But that doesn't work so well for
-                // immutable variables defined in a loop:
-                //     loop { let x; x = 5; }
-                // because the "assignment" loops back around and generates an error.
-                //
-                // So now we just check that variables defined w/o an
-                // initializer are not live at the point of their
-                // initialization, which is mildly more complex than checking
-                // once at the func header but otherwise equivalent.
-
-                if let Some(els) = local.els {
-                    // Eventually, `let pat: ty = init else { els };` is mostly equivalent to
-                    // `let (bindings, ...) = match init { pat => (bindings, ...), _ => els };`
-                    // except that extended lifetime applies at the `init` location.
-                    //
-                    //       (e)
-                    //        |
-                    //        v
-                    //      (expr)
-                    //      /   \
-                    //     |     |
-                    //     v     v
-                    // bindings  els
-                    //     |
-                    //     v
-                    // ( succ )
-                    //
-                    if let Some(init) = local.init {
-                        let else_ln = self.propagate_through_block(els, succ);
-                        let ln = self.live_node(local.hir_id, local.span);
-                        self.init_from_succ(ln, succ);
-                        self.merge_from_succ(ln, else_ln);
-                        let succ = self.propagate_through_expr(init, ln);
-                        self.define_bindings_in_pat(local.pat, succ)
-                    } else {
-                        span_bug!(
-                            stmt.span,
-                            "variable is uninitialized but an unexpected else branch is found"
-                        )
-                    }
-                } else {
-                    let succ = self.propagate_through_opt_expr(local.init, succ);
-                    self.define_bindings_in_pat(local.pat, succ)
-                }
-            }
-            hir::StmtKind::Item(..) => succ,
-            hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
-                self.propagate_through_expr(expr, succ)
-            }
-        }
-    }
-
-    fn propagate_through_exprs(&mut self, exprs: &[Expr<'_>], succ: LiveNode) -> LiveNode {
-        exprs.iter().rev().fold(succ, |succ, expr| self.propagate_through_expr(expr, succ))
-    }
-
-    fn propagate_through_opt_expr(
-        &mut self,
-        opt_expr: Option<&Expr<'_>>,
-        succ: LiveNode,
-    ) -> LiveNode {
-        opt_expr.map_or(succ, |expr| self.propagate_through_expr(expr, succ))
-    }
-
-    fn propagate_through_expr(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode {
-        debug!("propagate_through_expr: {:?}", expr);
-
-        match expr.kind {
-            // Interesting cases with control flow or which gen/kill
-            hir::ExprKind::Path(hir::QPath::Resolved(_, path)) => {
-                self.access_path(expr.hir_id, path, succ, ACC_READ | ACC_USE)
-            }
-
-            hir::ExprKind::Field(ref e, _) => self.propagate_through_expr(e, succ),
-
-            hir::ExprKind::Closure { .. } => {
-                debug!("{:?} is an ExprKind::Closure", expr);
-
-                // the construction of a closure itself is not important,
-                // but we have to consider the closed over variables.
-                let caps = self
-                    .ir
-                    .capture_info_map
-                    .get(&expr.hir_id)
-                    .cloned()
-                    .unwrap_or_else(|| span_bug!(expr.span, "no registered caps"));
-
-                caps.iter().rev().fold(succ, |succ, cap| {
-                    self.init_from_succ(cap.ln, succ);
-                    let var = self.variable(cap.var_hid, expr.span);
-                    self.acc(cap.ln, var, ACC_READ | ACC_USE);
-                    cap.ln
-                })
-            }
-
-            hir::ExprKind::Let(let_expr) => {
-                let succ = self.propagate_through_expr(let_expr.init, succ);
-                self.define_bindings_in_pat(let_expr.pat, succ)
-            }
-
-            // Note that labels have been resolved, so we don't need to look
-            // at the label ident
-            hir::ExprKind::Loop(ref blk, ..) => self.propagate_through_loop(expr, blk, succ),
-
-            hir::ExprKind::Yield(e, ..) => {
-                let yield_ln = self.live_node(expr.hir_id, expr.span);
-                self.init_from_succ(yield_ln, succ);
-                self.merge_from_succ(yield_ln, self.exit_ln);
-                self.propagate_through_expr(e, yield_ln)
-            }
-
-            hir::ExprKind::If(ref cond, ref then, ref else_opt) => {
-                //
-                //     (cond)
-                //       |
-                //       v
-                //     (expr)
-                //     /   \
-                //    |     |
-                //    v     v
-                //  (then)(els)
-                //    |     |
-                //    v     v
-                //   (  succ  )
-                //
-                let else_ln = self.propagate_through_opt_expr(else_opt.as_deref(), succ);
-                let then_ln = self.propagate_through_expr(then, succ);
-                let ln = self.live_node(expr.hir_id, expr.span);
-                self.init_from_succ(ln, else_ln);
-                self.merge_from_succ(ln, then_ln);
-                self.propagate_through_expr(cond, ln)
-            }
-
-            hir::ExprKind::Match(ref e, arms, _) => {
-                //
-                //      (e)
-                //       |
-                //       v
-                //     (expr)
-                //     / | \
-                //    |  |  |
-                //    v  v  v
-                //   (..arms..)
-                //    |  |  |
-                //    v  v  v
-                //   (  succ  )
-                //
-                //
-                let ln = self.live_node(expr.hir_id, expr.span);
-                self.init_empty(ln, succ);
-                for arm in arms {
-                    let body_succ = self.propagate_through_expr(arm.body, succ);
-
-                    let guard_succ = arm
-                        .guard
-                        .as_ref()
-                        .map_or(body_succ, |g| self.propagate_through_expr(g, body_succ));
-                    let arm_succ = self.define_bindings_in_pat(&arm.pat, guard_succ);
-                    self.merge_from_succ(ln, arm_succ);
-                }
-                self.propagate_through_expr(e, ln)
-            }
-
-            hir::ExprKind::Ret(ref o_e) => {
-                // Ignore succ and subst exit_ln.
-                self.propagate_through_opt_expr(o_e.as_deref(), self.exit_ln)
-            }
-
-            hir::ExprKind::Become(e) => {
-                // Ignore succ and subst exit_ln.
-                self.propagate_through_expr(e, self.exit_ln)
-            }
-
-            hir::ExprKind::Break(label, ref opt_expr) => {
-                // Find which label this break jumps to
-                let target = match label.target_id {
-                    Ok(hir_id) => self.break_ln.get(&hir_id),
-                    Err(err) => span_bug!(expr.span, "loop scope error: {}", err),
-                }
-                .cloned();
-
-                // Now that we know the label we're going to,
-                // look it up in the break loop nodes table
-
-                match target {
-                    Some(b) => self.propagate_through_opt_expr(opt_expr.as_deref(), b),
-                    None => span_bug!(expr.span, "`break` to unknown label"),
-                }
-            }
-
-            hir::ExprKind::Continue(label) => {
-                // Find which label this expr continues to
-                let sc = label
-                    .target_id
-                    .unwrap_or_else(|err| span_bug!(expr.span, "loop scope error: {}", err));
-
-                // Now that we know the label we're going to,
-                // look it up in the continue loop nodes table
-                self.cont_ln.get(&sc).cloned().unwrap_or_else(|| {
-                    // Liveness linting happens after building the THIR. Bad labels should already
-                    // have been caught.
-                    span_bug!(expr.span, "continue to unknown label");
-                })
-            }
-
-            hir::ExprKind::Assign(ref l, ref r, _) => {
-                // see comment on places in
-                // propagate_through_place_components()
-                let succ = self.write_place(l, succ, ACC_WRITE);
-                let succ = self.propagate_through_place_components(l, succ);
-                self.propagate_through_expr(r, succ)
-            }
-
-            hir::ExprKind::AssignOp(_, ref l, ref r) => {
-                // an overloaded assign op is like a method call
-                if self.typeck_results.is_method_call(expr) {
-                    let succ = self.propagate_through_expr(l, succ);
-                    self.propagate_through_expr(r, succ)
-                } else {
-                    // see comment on places in
-                    // propagate_through_place_components()
-                    let succ = self.write_place(l, succ, ACC_WRITE | ACC_READ);
-                    let succ = self.propagate_through_expr(r, succ);
-                    self.propagate_through_place_components(l, succ)
-                }
-            }
-
-            // Uninteresting cases: just propagate in rev exec order
-            hir::ExprKind::Array(exprs) => self.propagate_through_exprs(exprs, succ),
-
-            hir::ExprKind::Struct(_, fields, ref with_expr) => {
-                let succ = match with_expr {
-                    hir::StructTailExpr::Base(base) => {
-                        self.propagate_through_opt_expr(Some(base), succ)
-                    }
-                    hir::StructTailExpr::None | hir::StructTailExpr::DefaultFields(_) => succ,
-                };
-                fields
-                    .iter()
-                    .rev()
-                    .fold(succ, |succ, field| self.propagate_through_expr(field.expr, succ))
-            }
-
-            hir::ExprKind::Call(ref f, args) => {
-                let is_ctor = |f: &Expr<'_>| matches!(f.kind, hir::ExprKind::Path(hir::QPath::Resolved(_, path)) if matches!(path.res, rustc_hir::def::Res::Def(rustc_hir::def::DefKind::Ctor(_, _), _)));
-                let succ =
-                    if !is_ctor(f) { self.check_is_ty_uninhabited(expr, succ) } else { succ };
-
-                let succ = self.propagate_through_exprs(args, succ);
-                self.propagate_through_expr(f, succ)
-            }
-
-            hir::ExprKind::MethodCall(.., receiver, args, _) => {
-                let succ = self.check_is_ty_uninhabited(expr, succ);
-                let succ = self.propagate_through_exprs(args, succ);
-                self.propagate_through_expr(receiver, succ)
-            }
-
-            hir::ExprKind::Use(expr, _) => {
-                let succ = self.check_is_ty_uninhabited(expr, succ);
-                self.propagate_through_expr(expr, succ)
-            }
-
-            hir::ExprKind::Tup(exprs) => self.propagate_through_exprs(exprs, succ),
-
-            hir::ExprKind::Binary(op, ref l, ref r) if op.node.is_lazy() => {
-                let r_succ = self.propagate_through_expr(r, succ);
-
-                let ln = self.live_node(expr.hir_id, expr.span);
-                self.init_from_succ(ln, succ);
-                self.merge_from_succ(ln, r_succ);
-
-                self.propagate_through_expr(l, ln)
-            }
-
-            hir::ExprKind::Index(ref l, ref r, _) | hir::ExprKind::Binary(_, ref l, ref r) => {
-                let r_succ = self.propagate_through_expr(r, succ);
-                self.propagate_through_expr(l, r_succ)
-            }
-
-            hir::ExprKind::AddrOf(_, _, ref e)
-            | hir::ExprKind::Cast(ref e, _)
-            | hir::ExprKind::Type(ref e, _)
-            | hir::ExprKind::UnsafeBinderCast(_, ref e, _)
-            | hir::ExprKind::DropTemps(ref e)
-            | hir::ExprKind::Unary(_, ref e)
-            | hir::ExprKind::Repeat(ref e, _) => self.propagate_through_expr(e, succ),
-
-            hir::ExprKind::InlineAsm(asm) => {
-                //
-                //     (inputs)
-                //        |
-                //        v
-                //     (outputs)
-                //    /         \
-                //    |         |
-                //    v         v
-                // (labels)(fallthrough)
-                //    |         |
-                //    v         v
-                // ( succ / exit_ln )
-
-                // Handle non-returning asm
-                let mut succ =
-                    if self.typeck_results.expr_ty(expr).is_never() { self.exit_ln } else { succ };
-
-                // Do a first pass for labels only
-                if asm.contains_label() {
-                    let ln = self.live_node(expr.hir_id, expr.span);
-                    self.init_from_succ(ln, succ);
-                    for (op, _op_sp) in asm.operands.iter().rev() {
-                        match op {
-                            hir::InlineAsmOperand::Label { block } => {
-                                let label_ln = self.propagate_through_block(block, succ);
-                                self.merge_from_succ(ln, label_ln);
-                            }
-                            hir::InlineAsmOperand::In { .. }
-                            | hir::InlineAsmOperand::Out { .. }
-                            | hir::InlineAsmOperand::InOut { .. }
-                            | hir::InlineAsmOperand::SplitInOut { .. }
-                            | hir::InlineAsmOperand::Const { .. }
-                            | hir::InlineAsmOperand::SymFn { .. }
-                            | hir::InlineAsmOperand::SymStatic { .. } => {}
-                        }
-                    }
-                    succ = ln;
-                }
-
-                // Do a second pass for writing outputs only
-                for (op, _op_sp) in asm.operands.iter().rev() {
-                    match op {
-                        hir::InlineAsmOperand::In { .. }
-                        | hir::InlineAsmOperand::Const { .. }
-                        | hir::InlineAsmOperand::SymFn { .. }
-                        | hir::InlineAsmOperand::SymStatic { .. }
-                        | hir::InlineAsmOperand::Label { .. } => {}
-                        hir::InlineAsmOperand::Out { expr, .. } => {
-                            if let Some(expr) = expr {
-                                succ = self.write_place(expr, succ, ACC_WRITE);
-                            }
-                        }
-                        hir::InlineAsmOperand::InOut { expr, .. } => {
-                            succ = self.write_place(expr, succ, ACC_READ | ACC_WRITE | ACC_USE);
-                        }
-                        hir::InlineAsmOperand::SplitInOut { out_expr, .. } => {
-                            if let Some(expr) = out_expr {
-                                succ = self.write_place(expr, succ, ACC_WRITE);
-                            }
-                        }
-                    }
-                }
-
-                // Then do a third pass for inputs
-                for (op, _op_sp) in asm.operands.iter().rev() {
-                    match op {
-                        hir::InlineAsmOperand::In { expr, .. } => {
-                            succ = self.propagate_through_expr(expr, succ)
-                        }
-                        hir::InlineAsmOperand::Out { expr, .. } => {
-                            if let Some(expr) = expr {
-                                succ = self.propagate_through_place_components(expr, succ);
-                            }
-                        }
-                        hir::InlineAsmOperand::InOut { expr, .. } => {
-                            succ = self.propagate_through_place_components(expr, succ);
-                        }
-                        hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
-                            if let Some(expr) = out_expr {
-                                succ = self.propagate_through_place_components(expr, succ);
-                            }
-                            succ = self.propagate_through_expr(in_expr, succ);
-                        }
-                        hir::InlineAsmOperand::Const { .. }
-                        | hir::InlineAsmOperand::SymFn { .. }
-                        | hir::InlineAsmOperand::SymStatic { .. }
-                        | hir::InlineAsmOperand::Label { .. } => {}
-                    }
-                }
-                succ
-            }
-
-            hir::ExprKind::Lit(..)
-            | hir::ExprKind::ConstBlock(..)
-            | hir::ExprKind::Err(_)
-            | hir::ExprKind::Path(hir::QPath::TypeRelative(..))
-            | hir::ExprKind::Path(hir::QPath::LangItem(..))
-            | hir::ExprKind::OffsetOf(..) => succ,
-
-            // Note that labels have been resolved, so we don't need to look
-            // at the label ident
-            hir::ExprKind::Block(ref blk, _) => self.propagate_through_block(blk, succ),
-        }
-    }
-
-    fn propagate_through_place_components(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode {
-        // # Places
-        //
-        // In general, the full flow graph structure for an
-        // assignment/move/etc can be handled in one of two ways,
-        // depending on whether what is being assigned is a "tracked
-        // value" or not. A tracked value is basically a local
-        // variable or argument.
-        //
-        // The two kinds of graphs are:
-        //
-        //    Tracked place          Untracked place
-        // ----------------------++-----------------------
-        //                       ||
-        //         |             ||           |
-        //         v             ||           v
-        //     (rvalue)          ||       (rvalue)
-        //         |             ||           |
-        //         v             ||           v
-        // (write of place)      ||   (place components)
-        //         |             ||           |
-        //         v             ||           v
-        //      (succ)           ||        (succ)
-        //                       ||
-        // ----------------------++-----------------------
-        //
-        // I will cover the two cases in turn:
-        //
-        // # Tracked places
-        //
-        // A tracked place is a local variable/argument `x`. In
-        // these cases, the link_node where the write occurs is linked
-        // to node id of `x`. The `write_place()` routine generates
-        // the contents of this node. There are no subcomponents to
-        // consider.
-        //
-        // # Non-tracked places
-        //
-        // These are places like `x[5]` or `x.f`. In that case, we
-        // basically ignore the value which is written to but generate
-        // reads for the components---`x` in these two examples. The
-        // components reads are generated by
-        // `propagate_through_place_components()` (this fn).
-        //
-        // # Illegal places
-        //
-        // It is still possible to observe assignments to non-places;
-        // these errors are detected in the later pass borrowck. We
-        // just ignore such cases and treat them as reads.
-
-        match expr.kind {
-            hir::ExprKind::Path(_) => succ,
-            hir::ExprKind::Field(ref e, _) => self.propagate_through_expr(e, succ),
-            _ => self.propagate_through_expr(expr, succ),
-        }
-    }
-
-    // see comment on propagate_through_place()
-    fn write_place(&mut self, expr: &Expr<'_>, succ: LiveNode, acc: u32) -> LiveNode {
-        match expr.kind {
-            hir::ExprKind::Path(hir::QPath::Resolved(_, path)) => {
-                self.access_path(expr.hir_id, path, succ, acc)
-            }
-
-            // We do not track other places, so just propagate through
-            // to their subcomponents. Also, it may happen that
-            // non-places occur here, because those are detected in the
-            // later pass borrowck.
-            _ => succ,
-        }
-    }
-
-    fn access_var(
-        &mut self,
-        hir_id: HirId,
-        var_hid: HirId,
-        succ: LiveNode,
-        acc: u32,
-        span: Span,
-    ) -> LiveNode {
-        let ln = self.live_node(hir_id, span);
-        if acc != 0 {
-            self.init_from_succ(ln, succ);
-            let var = self.variable(var_hid, span);
-            self.acc(ln, var, acc);
-        }
-        ln
-    }
-
-    fn access_path(
-        &mut self,
-        hir_id: HirId,
-        path: &hir::Path<'_>,
-        succ: LiveNode,
-        acc: u32,
-    ) -> LiveNode {
-        match path.res {
-            Res::Local(hid) => self.access_var(hir_id, hid, succ, acc, path.span),
-            _ => succ,
-        }
-    }
-
-    fn propagate_through_loop(
-        &mut self,
-        expr: &Expr<'_>,
-        body: &hir::Block<'_>,
-        succ: LiveNode,
-    ) -> LiveNode {
-        /*
-        We model control flow like this:
-
-              (expr) <-+
-                |      |
-                v      |
-              (body) --+
-
-        Note that a `continue` expression targeting the `loop` will have a successor of `expr`.
-        Meanwhile, a `break` expression will have a successor of `succ`.
-        */
-
-        // first iteration:
-        let ln = self.live_node(expr.hir_id, expr.span);
-        self.init_empty(ln, succ);
-        debug!("propagate_through_loop: using id for loop body {} {:?}", expr.hir_id, body);
-
-        self.break_ln.insert(expr.hir_id, succ);
-
-        self.cont_ln.insert(expr.hir_id, ln);
-
-        let body_ln = self.propagate_through_block(body, ln);
-
-        // repeat until fixed point is reached:
-        while self.merge_from_succ(ln, body_ln) {
-            assert_eq!(body_ln, self.propagate_through_block(body, ln));
-        }
-
-        ln
-    }
-
-    fn check_is_ty_uninhabited(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode {
-        let ty = self.typeck_results.expr_ty(expr);
-        let m = self.ir.tcx.parent_module(expr.hir_id).to_def_id();
-        if ty.is_inhabited_from(self.ir.tcx, m, self.typing_env) {
-            return succ;
-        }
-        match self.ir.lnks[succ] {
-            LiveNodeKind::ExprNode(succ_span, succ_id) => {
-                self.warn_about_unreachable(expr.span, ty, succ_span, succ_id, "expression");
-            }
-            LiveNodeKind::VarDefNode(succ_span, succ_id) => {
-                self.warn_about_unreachable(expr.span, ty, succ_span, succ_id, "definition");
-            }
-            _ => {}
-        };
-        self.exit_ln
-    }
-
-    fn warn_about_unreachable<'desc>(
-        &mut self,
-        orig_span: Span,
-        orig_ty: Ty<'tcx>,
-        expr_span: Span,
-        expr_id: HirId,
-        descr: &'desc str,
-    ) {
-        if !orig_ty.is_never() {
-            // Unreachable code warnings are already emitted during type checking.
-            // However, during type checking, full type information is being
-            // calculated but not yet available, so the check for diverging
-            // expressions due to uninhabited result types is pretty crude and
-            // only checks whether ty.is_never(). Here, we have full type
-            // information available and can issue warnings for less obviously
-            // uninhabited types (e.g. empty enums). The check above is used so
-            // that we do not emit the same warning twice if the uninhabited type
-            // is indeed `!`.
-
-            self.ir.tcx.emit_node_span_lint(
-                lint::builtin::UNREACHABLE_CODE,
-                expr_id,
-                expr_span,
-                errors::UnreachableDueToUninhabited {
-                    expr: expr_span,
-                    orig: orig_span,
-                    descr,
-                    ty: orig_ty,
-                },
-            );
-        }
-    }
-}
-
-// _______________________________________________________________________
-// Checking for error conditions
-
-impl<'a, 'tcx> Visitor<'tcx> for Liveness<'a, 'tcx> {
-    fn visit_local(&mut self, local: &'tcx hir::LetStmt<'tcx>) {
-        self.check_unused_vars_in_pat(local.pat, None, None, |spans, hir_id, ln, var| {
-            if local.init.is_some() {
-                self.warn_about_dead_assign(spans, hir_id, ln, var, None);
-            }
-        });
-
-        intravisit::walk_local(self, local);
-    }
-
-    fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) {
-        check_expr(self, ex);
-        intravisit::walk_expr(self, ex);
-    }
-
-    fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) {
-        self.check_unused_vars_in_pat(arm.pat, None, None, |_, _, _, _| {});
-        intravisit::walk_arm(self, arm);
-    }
-}
-
-fn check_expr<'tcx>(this: &mut Liveness<'_, 'tcx>, expr: &'tcx Expr<'tcx>) {
-    match expr.kind {
-        hir::ExprKind::Assign(ref l, ..) => {
-            this.check_place(l);
-        }
-
-        hir::ExprKind::AssignOp(_, ref l, _) => {
-            if !this.typeck_results.is_method_call(expr) {
-                this.check_place(l);
-            }
-        }
-
-        hir::ExprKind::InlineAsm(asm) => {
-            for (op, _op_sp) in asm.operands {
-                match op {
-                    hir::InlineAsmOperand::Out { expr, .. } => {
-                        if let Some(expr) = expr {
-                            this.check_place(expr);
-                        }
-                    }
-                    hir::InlineAsmOperand::InOut { expr, .. } => {
-                        this.check_place(expr);
-                    }
-                    hir::InlineAsmOperand::SplitInOut { out_expr, .. } => {
-                        if let Some(out_expr) = out_expr {
-                            this.check_place(out_expr);
-                        }
-                    }
-                    _ => {}
-                }
-            }
-        }
-
-        hir::ExprKind::Let(let_expr) => {
-            this.check_unused_vars_in_pat(let_expr.pat, None, None, |_, _, _, _| {});
-        }
-
-        // no correctness conditions related to liveness
-        hir::ExprKind::Call(..)
-        | hir::ExprKind::MethodCall(..)
-        | hir::ExprKind::Use(..)
-        | hir::ExprKind::Match(..)
-        | hir::ExprKind::Loop(..)
-        | hir::ExprKind::Index(..)
-        | hir::ExprKind::Field(..)
-        | hir::ExprKind::Array(..)
-        | hir::ExprKind::Tup(..)
-        | hir::ExprKind::Binary(..)
-        | hir::ExprKind::Cast(..)
-        | hir::ExprKind::If(..)
-        | hir::ExprKind::DropTemps(..)
-        | hir::ExprKind::Unary(..)
-        | hir::ExprKind::Ret(..)
-        | hir::ExprKind::Become(..)
-        | hir::ExprKind::Break(..)
-        | hir::ExprKind::Continue(..)
-        | hir::ExprKind::Lit(_)
-        | hir::ExprKind::ConstBlock(..)
-        | hir::ExprKind::Block(..)
-        | hir::ExprKind::AddrOf(..)
-        | hir::ExprKind::OffsetOf(..)
-        | hir::ExprKind::Struct(..)
-        | hir::ExprKind::Repeat(..)
-        | hir::ExprKind::Closure { .. }
-        | hir::ExprKind::Path(_)
-        | hir::ExprKind::Yield(..)
-        | hir::ExprKind::Type(..)
-        | hir::ExprKind::UnsafeBinderCast(..)
-        | hir::ExprKind::Err(_) => {}
-    }
-}
-
-impl<'tcx> Liveness<'_, 'tcx> {
-    fn check_place(&mut self, expr: &'tcx Expr<'tcx>) {
-        match expr.kind {
-            hir::ExprKind::Path(hir::QPath::Resolved(_, path)) => {
-                if let Res::Local(var_hid) = path.res {
-                    // Assignment to an immutable variable or argument: only legal
-                    // if there is no later assignment. If this local is actually
-                    // mutable, then check for a reassignment to flag the mutability
-                    // as being used.
-                    let ln = self.live_node(expr.hir_id, expr.span);
-                    let var = self.variable(var_hid, expr.span);
-                    let sugg = self.annotate_mut_binding_to_immutable_binding(var_hid, expr);
-                    self.warn_about_dead_assign(vec![expr.span], expr.hir_id, ln, var, sugg);
-                }
-            }
-            _ => {
-                // For other kinds of places, no checks are required,
-                // and any embedded expressions are actually rvalues
-                intravisit::walk_expr(self, expr);
-            }
-        }
-    }
-
-    fn should_warn(&self, var: Variable) -> Option<String> {
-        let name = self.ir.variable_name(var);
-        let name = name.as_str();
-        if name.as_bytes()[0] == b'_' {
-            return None;
-        }
-        Some(name.to_owned())
-    }
-
-    fn warn_about_unused_upvars(&self, entry_ln: LiveNode) {
-        let Some(closure_min_captures) = self.closure_min_captures else {
-            return;
-        };
-
-        // If closure_min_captures is Some(), upvars must be Some() too.
-        for (&var_hir_id, min_capture_list) in closure_min_captures {
-            for captured_place in min_capture_list {
-                match captured_place.info.capture_kind {
-                    ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => {}
-                    ty::UpvarCapture::ByRef(..) => continue,
-                };
-                let span = captured_place.get_capture_kind_span(self.ir.tcx);
-                let var = self.variable(var_hir_id, span);
-                if self.used_on_entry(entry_ln, var) {
-                    if !self.live_on_entry(entry_ln, var) {
-                        if let Some(name) = self.should_warn(var) {
-                            self.ir.tcx.emit_node_span_lint(
-                                lint::builtin::UNUSED_ASSIGNMENTS,
-                                var_hir_id,
-                                vec![span],
-                                errors::UnusedCaptureMaybeCaptureRef { name },
-                            );
-                        }
-                    }
-                } else if let Some(name) = self.should_warn(var) {
-                    self.ir.tcx.emit_node_span_lint(
-                        lint::builtin::UNUSED_VARIABLES,
-                        var_hir_id,
-                        vec![span],
-                        errors::UnusedVarMaybeCaptureRef { name },
-                    );
-                }
-            }
-        }
-    }
-
-    fn warn_about_unused_args(&self, body: &hir::Body<'_>, entry_ln: LiveNode) {
-        if let Some(intrinsic) = self.ir.tcx.intrinsic(self.ir.tcx.hir_body_owner_def_id(body.id()))
-        {
-            if intrinsic.must_be_overridden {
-                return;
-            }
-        }
-
-        for p in body.params {
-            self.check_unused_vars_in_pat(
-                p.pat,
-                Some(entry_ln),
-                Some(body),
-                |spans, hir_id, ln, var| {
-                    if !self.live_on_entry(ln, var)
-                        && let Some(name) = self.should_warn(var)
-                    {
-                        self.ir.tcx.emit_node_span_lint(
-                            lint::builtin::UNUSED_ASSIGNMENTS,
-                            hir_id,
-                            spans,
-                            errors::UnusedAssignPassed { name },
-                        );
-                    }
-                },
-            );
-        }
-    }
-
-    fn check_unused_vars_in_pat(
-        &self,
-        pat: &hir::Pat<'_>,
-        entry_ln: Option<LiveNode>,
-        opt_body: Option<&hir::Body<'_>>,
-        on_used_on_entry: impl Fn(Vec<Span>, HirId, LiveNode, Variable),
-    ) {
-        // In an or-pattern, only consider the variable; any later patterns must have the same
-        // bindings, and we also consider the first pattern to be the "authoritative" set of ids.
-        // However, we should take the ids and spans of variables with the same name from the later
-        // patterns so the suggestions to prefix with underscores will apply to those too.
-        let mut vars: FxIndexMap<Symbol, (LiveNode, Variable, Vec<(HirId, Span, Span)>)> =
-            <_>::default();
-
-        pat.each_binding(|_, hir_id, pat_sp, ident| {
-            let ln = entry_ln.unwrap_or_else(|| self.live_node(hir_id, pat_sp));
-            let var = self.variable(hir_id, ident.span);
-            let id_and_sp = (hir_id, pat_sp, ident.span);
-            vars.entry(self.ir.variable_name(var))
-                .and_modify(|(.., hir_ids_and_spans)| hir_ids_and_spans.push(id_and_sp))
-                .or_insert_with(|| (ln, var, vec![id_and_sp]));
-        });
-
-        let can_remove = match pat.kind {
-            hir::PatKind::Struct(_, fields, Some(_)) => {
-                // if all fields are shorthand, remove the struct field, otherwise, mark with _ as prefix
-                fields.iter().all(|f| f.is_shorthand)
-            }
-            _ => false,
-        };
-
-        for (_, (ln, var, hir_ids_and_spans)) in vars {
-            if self.used_on_entry(ln, var) {
-                let id = hir_ids_and_spans[0].0;
-                let spans =
-                    hir_ids_and_spans.into_iter().map(|(_, _, ident_span)| ident_span).collect();
-                on_used_on_entry(spans, id, ln, var);
-            } else {
-                self.report_unused(hir_ids_and_spans, ln, var, can_remove, pat, opt_body);
-            }
-        }
-    }
-
-    /// Detect the following case
-    ///
-    /// ```text
-    /// fn change_object(mut a: &Ty) {
-    ///     let a = Ty::new();
-    ///     b = &a;
-    /// }
-    /// ```
-    ///
-    /// where the user likely meant to modify the value behind there reference, use `a` as an out
-    /// parameter, instead of mutating the local binding. When encountering this we suggest:
-    ///
-    /// ```text
-    /// fn change_object(a: &'_ mut Ty) {
-    ///     let a = Ty::new();
-    ///     *b = a;
-    /// }
-    /// ```
-    fn annotate_mut_binding_to_immutable_binding(
-        &self,
-        var_hid: HirId,
-        expr: &'tcx Expr<'tcx>,
-    ) -> Option<errors::UnusedAssignSuggestion> {
-        if let hir::Node::Expr(parent) = self.ir.tcx.parent_hir_node(expr.hir_id)
-            && let hir::ExprKind::Assign(_, rhs, _) = parent.kind
-            && let hir::ExprKind::AddrOf(borrow_kind, _mut, inner) = rhs.kind
-            && let hir::BorrowKind::Ref = borrow_kind
-            && let hir::Node::Pat(pat) = self.ir.tcx.hir_node(var_hid)
-            && let hir::Node::Param(hir::Param { ty_span, .. }) =
-                self.ir.tcx.parent_hir_node(pat.hir_id)
-            && let item_id = self.ir.tcx.hir_get_parent_item(pat.hir_id)
-            && let item = self.ir.tcx.hir_owner_node(item_id)
-            && let Some(fn_decl) = item.fn_decl()
-            && let hir::PatKind::Binding(hir::BindingMode::MUT, _hir_id, ident, _) = pat.kind
-            && let Some((lt, mut_ty)) = fn_decl
-                .inputs
-                .iter()
-                .filter_map(|ty| {
-                    if ty.span == *ty_span
-                        && let hir::TyKind::Ref(lt, mut_ty) = ty.kind
-                    {
-                        Some((lt, mut_ty))
-                    } else {
-                        None
-                    }
-                })
-                .next()
-        {
-            let ty_span = if mut_ty.mutbl.is_mut() {
-                // Leave `&'name mut Ty` and `&mut Ty` as they are (#136028).
-                None
-            } else {
-                // `&'name Ty` -> `&'name mut Ty` or `&Ty` -> `&mut Ty`
-                Some(mut_ty.ty.span.shrink_to_lo())
-            };
-            let pre = if lt.ident.span.is_empty() { "" } else { " " };
-            Some(errors::UnusedAssignSuggestion {
-                ty_span,
-                pre,
-                ty_ref_span: pat.span.until(ident.span),
-                ident_span: expr.span.shrink_to_lo(),
-                expr_ref_span: rhs.span.until(inner.span),
-            })
-        } else {
-            None
-        }
-    }
-
-    #[instrument(skip(self), level = "INFO")]
-    fn report_unused(
-        &self,
-        hir_ids_and_spans: Vec<(HirId, Span, Span)>,
-        ln: LiveNode,
-        var: Variable,
-        can_remove: bool,
-        pat: &hir::Pat<'_>,
-        opt_body: Option<&hir::Body<'_>>,
-    ) {
-        let first_hir_id = hir_ids_and_spans[0].0;
-        if let Some(name) = self.should_warn(var).filter(|name| name != "self") {
-            // annoying: for parameters in funcs like `fn(x: i32)
-            // {ret}`, there is only one node, so asking about
-            // assigned_on_exit() is not meaningful.
-            let is_assigned =
-                if ln == self.exit_ln { false } else { self.assigned_on_exit(ln, var) };
-
-            let mut typo = None;
-            let filtered_hir_ids_and_spans = hir_ids_and_spans.iter().filter(|(hir_id, ..)| {
-                !matches!(self.ir.tcx.parent_hir_node(*hir_id), hir::Node::Param(_))
-            });
-            for (hir_id, _, span) in filtered_hir_ids_and_spans.clone() {
-                let ty = self.typeck_results.node_type(*hir_id);
-                if let ty::Adt(adt, _) = ty.peel_refs().kind() {
-                    let name = Symbol::intern(&name);
-                    let adt_def = self.ir.tcx.adt_def(adt.did());
-                    let variant_names: Vec<_> = adt_def
-                        .variants()
-                        .iter()
-                        .filter(|v| matches!(v.ctor, Some((CtorKind::Const, _))))
-                        .map(|v| v.name)
-                        .collect();
-                    if let Some(name) = find_best_match_for_name(&variant_names, name, None)
-                        && let Some(variant) = adt_def.variants().iter().find(|v| {
-                            v.name == name && matches!(v.ctor, Some((CtorKind::Const, _)))
-                        })
-                    {
-                        typo = Some(errors::PatternTypo {
-                            span: *span,
-                            code: with_no_trimmed_paths!(self.ir.tcx.def_path_str(variant.def_id)),
-                            kind: self.ir.tcx.def_descr(variant.def_id).to_string(),
-                            item_name: variant.name.to_string(),
-                        });
-                    }
-                }
-            }
-            if typo.is_none() {
-                for (hir_id, _, span) in filtered_hir_ids_and_spans {
-                    let ty = self.typeck_results.node_type(*hir_id);
-                    // Look for consts of the same type with similar names as well, not just unit
-                    // structs and variants.
-                    for def_id in self.ir.tcx.hir_body_owners() {
-                        if let DefKind::Const = self.ir.tcx.def_kind(def_id)
-                            && self.ir.tcx.type_of(def_id).instantiate_identity() == ty
-                        {
-                            typo = Some(errors::PatternTypo {
-                                span: *span,
-                                code: with_no_trimmed_paths!(self.ir.tcx.def_path_str(def_id)),
-                                kind: "constant".to_string(),
-                                item_name: self.ir.tcx.item_name(def_id).to_string(),
-                            });
-                        }
-                    }
-                }
-            }
-            if is_assigned {
-                self.ir.tcx.emit_node_span_lint(
-                    lint::builtin::UNUSED_VARIABLES,
-                    first_hir_id,
-                    hir_ids_and_spans
-                        .into_iter()
-                        .map(|(_, _, ident_span)| ident_span)
-                        .collect::<Vec<_>>(),
-                    errors::UnusedVarAssignedOnly { name, typo },
-                )
-            } else if can_remove {
-                let spans = hir_ids_and_spans
-                    .iter()
-                    .map(|(_, pat_span, _)| {
-                        let span = self
-                            .ir
-                            .tcx
-                            .sess
-                            .source_map()
-                            .span_extend_to_next_char(*pat_span, ',', true);
-                        span.with_hi(BytePos(span.hi().0 + 1))
-                    })
-                    .collect();
-                self.ir.tcx.emit_node_span_lint(
-                    lint::builtin::UNUSED_VARIABLES,
-                    first_hir_id,
-                    hir_ids_and_spans.iter().map(|(_, pat_span, _)| *pat_span).collect::<Vec<_>>(),
-                    errors::UnusedVarRemoveField {
-                        name,
-                        sugg: errors::UnusedVarRemoveFieldSugg { spans },
-                    },
-                );
-            } else {
-                let (shorthands, non_shorthands): (Vec<_>, Vec<_>) =
-                    hir_ids_and_spans.iter().copied().partition(|(hir_id, _, ident_span)| {
-                        let var = self.variable(*hir_id, *ident_span);
-                        self.ir.variable_is_shorthand(var)
-                    });
-
-                // If we have both shorthand and non-shorthand, prefer the "try ignoring
-                // the field" message, and suggest `_` for the non-shorthands. If we only
-                // have non-shorthand, then prefix with an underscore instead.
-                if !shorthands.is_empty() {
-                    let shorthands =
-                        shorthands.into_iter().map(|(_, pat_span, _)| pat_span).collect();
-                    let non_shorthands =
-                        non_shorthands.into_iter().map(|(_, pat_span, _)| pat_span).collect();
-
-                    self.ir.tcx.emit_node_span_lint(
-                        lint::builtin::UNUSED_VARIABLES,
-                        first_hir_id,
-                        hir_ids_and_spans
-                            .iter()
-                            .map(|(_, pat_span, _)| *pat_span)
-                            .collect::<Vec<_>>(),
-                        errors::UnusedVarTryIgnore {
-                            name: name.clone(),
-                            sugg: errors::UnusedVarTryIgnoreSugg {
-                                shorthands,
-                                non_shorthands,
-                                name,
-                            },
-                        },
-                    );
-                } else {
-                    // #117284, when `pat_span` and `ident_span` have different contexts
-                    // we can't provide a good suggestion, instead we pointed out the spans from macro
-                    let from_macro = non_shorthands
-                        .iter()
-                        .find(|(_, pat_span, ident_span)| {
-                            !pat_span.eq_ctxt(*ident_span) && pat_span.from_expansion()
-                        })
-                        .map(|(_, pat_span, _)| *pat_span);
-                    let non_shorthands = non_shorthands
-                        .into_iter()
-                        .map(|(_, _, ident_span)| ident_span)
-                        .collect::<Vec<_>>();
-
-                    let suggestions = self.string_interp_suggestions(&name, opt_body);
-                    let sugg = if let Some(span) = from_macro {
-                        errors::UnusedVariableSugg::NoSugg { span, name: name.clone() }
-                    } else {
-                        errors::UnusedVariableSugg::TryPrefixSugg {
-                            spans: non_shorthands,
-                            name: name.clone(),
-                        }
-                    };
-
-                    self.ir.tcx.emit_node_span_lint(
-                        lint::builtin::UNUSED_VARIABLES,
-                        first_hir_id,
-                        hir_ids_and_spans
-                            .iter()
-                            .map(|(_, _, ident_span)| *ident_span)
-                            .collect::<Vec<_>>(),
-                        errors::UnusedVariableTryPrefix {
-                            label: if !suggestions.is_empty() { Some(pat.span) } else { None },
-                            name,
-                            sugg,
-                            string_interp: suggestions,
-                            typo,
-                        },
-                    );
-                }
-            }
-        }
-    }
-
-    fn string_interp_suggestions(
-        &self,
-        name: &str,
-        opt_body: Option<&hir::Body<'_>>,
-    ) -> Vec<errors::UnusedVariableStringInterp> {
-        let mut suggs = Vec::new();
-        let Some(opt_body) = opt_body else {
-            return suggs;
-        };
-        let mut visitor = CollectLitsVisitor { lit_exprs: vec![] };
-        intravisit::walk_body(&mut visitor, opt_body);
-        for lit_expr in visitor.lit_exprs {
-            let hir::ExprKind::Lit(litx) = &lit_expr.kind else { continue };
-            let rustc_ast::LitKind::Str(syb, _) = litx.node else {
-                continue;
-            };
-            let name_str: &str = syb.as_str();
-            let name_pa = format!("{{{name}}}");
-            if name_str.contains(&name_pa) {
-                suggs.push(errors::UnusedVariableStringInterp {
-                    lit: lit_expr.span,
-                    lo: lit_expr.span.shrink_to_lo(),
-                    hi: lit_expr.span.shrink_to_hi(),
-                });
-            }
-        }
-        suggs
-    }
-
-    fn warn_about_dead_assign(
-        &self,
-        spans: Vec<Span>,
-        hir_id: HirId,
-        ln: LiveNode,
-        var: Variable,
-        suggestion: Option<errors::UnusedAssignSuggestion>,
-    ) {
-        if !self.live_on_exit(ln, var)
-            && let Some(name) = self.should_warn(var)
-        {
-            let help = suggestion.is_none();
-            self.ir.tcx.emit_node_span_lint(
-                lint::builtin::UNUSED_ASSIGNMENTS,
-                hir_id,
-                spans,
-                errors::UnusedAssign { name, suggestion, help },
-            );
-        }
-    }
-}

compiler/rustc_passes/src/liveness/rwu_table.rs

@@ -1,146 +0,0 @@
-use std::iter;
-
-use crate::liveness::{LiveNode, Variable};
-
-#[derive(Clone, Copy)]
-pub(super) struct RWU {
-    pub(super) reader: bool,
-    pub(super) writer: bool,
-    pub(super) used: bool,
-}
-
-/// Conceptually, this is like a `Vec<Vec<RWU>>`. But the number of
-/// RWU's can get very large, so it uses a more compact representation.
-pub(super) struct RWUTable {
-    /// Total number of live nodes.
-    live_nodes: usize,
-    /// Total number of variables.
-    vars: usize,
-
-    /// A compressed representation of `RWU`s.
-    ///
-    /// Each word represents 2 different `RWU`s packed together. Each packed RWU
-    /// is stored in 4 bits: a reader bit, a writer bit, a used bit and a
-    /// padding bit.
-    ///
-    /// The data for each live node is contiguous and starts at a word boundary,
-    /// so there might be an unused space left.
-    words: Vec<u8>,
-    /// Number of words per each live node.
-    live_node_words: usize,
-}
-
-impl RWUTable {
-    const RWU_READER: u8 = 0b0001;
-    const RWU_WRITER: u8 = 0b0010;
-    const RWU_USED: u8 = 0b0100;
-    const RWU_MASK: u8 = 0b1111;
-
-    /// Size of packed RWU in bits.
-    const RWU_BITS: usize = 4;
-    /// Size of a word in bits.
-    const WORD_BITS: usize = size_of::<u8>() * 8;
-    /// Number of packed RWUs that fit into a single word.
-    const WORD_RWU_COUNT: usize = Self::WORD_BITS / Self::RWU_BITS;
-
-    pub(super) fn new(live_nodes: usize, vars: usize) -> RWUTable {
-        let live_node_words = vars.div_ceil(Self::WORD_RWU_COUNT);
-        Self { live_nodes, vars, live_node_words, words: vec![0u8; live_node_words * live_nodes] }
-    }
-
-    fn word_and_shift(&self, ln: LiveNode, var: Variable) -> (usize, u32) {
-        assert!(ln.index() < self.live_nodes);
-        assert!(var.index() < self.vars);
-
-        let var = var.index();
-        let word = var / Self::WORD_RWU_COUNT;
-        let shift = Self::RWU_BITS * (var % Self::WORD_RWU_COUNT);
-        (ln.index() * self.live_node_words + word, shift as u32)
-    }
-
-    fn pick2_rows_mut(&mut self, a: LiveNode, b: LiveNode) -> (&mut [u8], &mut [u8]) {
-        assert!(a.index() < self.live_nodes);
-        assert!(b.index() < self.live_nodes);
-        assert!(a != b);
-
-        let a_start = a.index() * self.live_node_words;
-        let b_start = b.index() * self.live_node_words;
-
-        unsafe {
-            let ptr = self.words.as_mut_ptr();
-            (
-                std::slice::from_raw_parts_mut(ptr.add(a_start), self.live_node_words),
-                std::slice::from_raw_parts_mut(ptr.add(b_start), self.live_node_words),
-            )
-        }
-    }
-
-    pub(super) fn copy(&mut self, dst: LiveNode, src: LiveNode) {
-        if dst == src {
-            return;
-        }
-
-        let (dst_row, src_row) = self.pick2_rows_mut(dst, src);
-        dst_row.copy_from_slice(src_row);
-    }
-
-    /// Sets `dst` to the union of `dst` and `src`, returns true if `dst` was
-    /// changed.
-    pub(super) fn union(&mut self, dst: LiveNode, src: LiveNode) -> bool {
-        if dst == src {
-            return false;
-        }
-
-        let mut changed = false;
-        let (dst_row, src_row) = self.pick2_rows_mut(dst, src);
-        for (dst_word, src_word) in iter::zip(dst_row, &*src_row) {
-            let old = *dst_word;
-            let new = *dst_word | src_word;
-            *dst_word = new;
-            changed |= old != new;
-        }
-        changed
-    }
-
-    pub(super) fn get_reader(&self, ln: LiveNode, var: Variable) -> bool {
-        let (word, shift) = self.word_and_shift(ln, var);
-        (self.words[word] >> shift) & Self::RWU_READER != 0
-    }
-
-    pub(super) fn get_writer(&self, ln: LiveNode, var: Variable) -> bool {
-        let (word, shift) = self.word_and_shift(ln, var);
-        (self.words[word] >> shift) & Self::RWU_WRITER != 0
-    }
-
-    pub(super) fn get_used(&self, ln: LiveNode, var: Variable) -> bool {
-        let (word, shift) = self.word_and_shift(ln, var);
-        (self.words[word] >> shift) & Self::RWU_USED != 0
-    }
-
-    pub(super) fn get(&self, ln: LiveNode, var: Variable) -> RWU {
-        let (word, shift) = self.word_and_shift(ln, var);
-        let rwu_packed = self.words[word] >> shift;
-        RWU {
-            reader: rwu_packed & Self::RWU_READER != 0,
-            writer: rwu_packed & Self::RWU_WRITER != 0,
-            used: rwu_packed & Self::RWU_USED != 0,
-        }
-    }
-
-    pub(super) fn set(&mut self, ln: LiveNode, var: Variable, rwu: RWU) {
-        let mut packed = 0;
-        if rwu.reader {
-            packed |= Self::RWU_READER;
-        }
-        if rwu.writer {
-            packed |= Self::RWU_WRITER;
-        }
-        if rwu.used {
-            packed |= Self::RWU_USED;
-        }
-
-        let (word, shift) = self.word_and_shift(ln, var);
-        let word = &mut self.words[word];
-        *word = (*word & !(Self::RWU_MASK << shift)) | (packed << shift)
-    }
-}

library/std/src/sync/poison.rs

@@ -60,6 +60,9 @@
 //!   while it is locked exclusively (write mode). If a panic occurs in any reader,
 //!   then the lock will not be poisoned.
 
+// If we are not unwinding, `PoisonError` is uninhabited.
+#![cfg_attr(not(panic = "unwind"), expect(unreachable_code))]
+
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::condvar::Condvar;
 #[unstable(feature = "mapped_lock_guards", issue = "117108")]

src/tools/clippy/tests/ui/needless_match.fixed

@@ -1,7 +1,7 @@
 #![warn(clippy::needless_match)]
 #![allow(clippy::manual_map)]
 #![allow(dead_code)]
-
+#![allow(unused)]
 #[derive(Clone, Copy)]
 enum Simple {
     A,

src/tools/clippy/tests/ui/needless_match.rs

@@ -1,7 +1,7 @@
 #![warn(clippy::needless_match)]
 #![allow(clippy::manual_map)]
 #![allow(dead_code)]
-
+#![allow(unused)]
 #[derive(Clone, Copy)]
 enum Simple {
     A,

src/tools/clippy/tests/ui/useless_conversion.fixed

@@ -1,5 +1,5 @@
 #![deny(clippy::useless_conversion)]
-#![allow(clippy::needless_if, clippy::unnecessary_wraps)]
+#![allow(clippy::needless_if, clippy::unnecessary_wraps, unused)]
 // FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
 #![allow(static_mut_refs)]
 

src/tools/clippy/tests/ui/useless_conversion.rs

@@ -1,5 +1,5 @@
 #![deny(clippy::useless_conversion)]
-#![allow(clippy::needless_if, clippy::unnecessary_wraps)]
+#![allow(clippy::needless_if, clippy::unnecessary_wraps, unused)]
 // FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
 #![allow(static_mut_refs)]
 

src/tools/miri/tests/fail/function_calls/arg_inplace_locals_alias.rs

@@ -4,7 +4,10 @@
 //@[tree]compile-flags: -Zmiri-tree-borrows
 // Validation forces more things into memory, which we can't have here.
 //@compile-flags: -Zmiri-disable-validation
+
 #![feature(custom_mir, core_intrinsics)]
+#![allow(unused)]
+
 use std::intrinsics::mir::*;
 
 pub struct S(i32);

src/tools/miri/tests/fail/function_calls/arg_inplace_observe_after.rs

@@ -22,6 +22,7 @@ fn main() {
     }
 }
 
+#[expect(unused_variables, unused_assignments)]
 pub fn change_arg(mut x: S) {
     x.0 = 0;
 }

src/tools/miri/tests/fail/function_calls/arg_inplace_observe_during.rs

@@ -23,6 +23,7 @@ fn main() {
     }
 }
 
+#[expect(unused_variables, unused_assignments)]
 pub fn change_arg(mut x: S, ptr: *mut S) {
     x.0 = 0;
     // If `x` got passed in-place, we'd see the write through `ptr`!

src/tools/miri/tests/pass/align_repeat_into_well_aligned_array.rs

@@ -2,6 +2,7 @@
 
 use std::mem::size_of;
 
+#[expect(unused_variables, unused_assignments)]
 fn main() {
     let mut a = Params::new();
     // The array itself here happens to be quite well-aligned, but not all its elements have that

src/tools/rust-analyzer/crates/ide-db/src/imports/merge_imports.rs

@@ -405,6 +405,8 @@ fn recursive_normalize(use_tree: &ast::UseTree, style: NormalizationStyle) -> Op
                 } else {
                     ted::replace_with_many(subtree.syntax(), elements);
                 }
+                // Silence unused assignment warning on `modified`.
+                let _ = modified;
                 modified = true;
             } else {
                 modified |= recursive_normalize(&subtree, NormalizationStyle::Default).is_some();

src/tools/rust-analyzer/crates/test-fixture/src/lib.rs

@@ -383,6 +383,8 @@ pub fn parse_with_proc_macros(
             }
         }
 
+        let _ = file_id;
+
         let root = match current_source_root_kind {
             SourceRootKind::Local => SourceRoot::new_local(mem::take(&mut file_set)),
             SourceRootKind::Library => SourceRoot::new_library(mem::take(&mut file_set)),

tests/ui/asm/x86_64/goto.rs

@@ -69,6 +69,7 @@ fn goto_out_jump() {
 fn goto_out_jump_noreturn() {
     unsafe {
         let mut value = false;
+        //~^ WARN value assigned to `value` is never read
         let mut out: usize;
         asm!(
             "lea {}, [{} + 1]",

tests/ui/asm/x86_64/goto.stderr

@@ -1,5 +1,5 @@
 warning: unreachable statement
-  --> $DIR/goto.rs:144:9
+  --> $DIR/goto.rs:145:9
    |
 LL | /         asm!(
 LL | |             "jmp {}",
@@ -13,10 +13,19 @@ LL |           unreachable!();
    |           ^^^^^^^^^^^^^^ unreachable statement
    |
 note: the lint level is defined here
-  --> $DIR/goto.rs:134:8
+  --> $DIR/goto.rs:135:8
    |
 LL | #[warn(unreachable_code)]
    |        ^^^^^^^^^^^^^^^^
 
-warning: 1 warning emitted
+warning: value assigned to `value` is never read
+  --> $DIR/goto.rs:71:25
+   |
+LL |         let mut value = false;
+   |                         ^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+   = note: `#[warn(unused_assignments)]` (part of `#[warn(unused)]`) on by default
+
+warning: 2 warnings emitted
 

tests/ui/async-await/async-closures/precise-captures.rs

@@ -10,6 +10,7 @@
 //   in <https://github.com/rust-lang/rust/pull/123350>.
 
 #![allow(unused_mut)]
+#![allow(unused_assignments)]
 
 extern crate block_on;
 

tests/ui/borrowck/borrowck-assign-to-subfield.rs

@@ -1,5 +1,6 @@
 //@ run-pass
 
+#[allow(unused)]
 pub fn main() {
     struct A {
         a: isize,

tests/ui/closures/2229_closure_analysis/diagnostics/liveness.rs

@@ -13,13 +13,11 @@ struct Point {
 
 pub fn f() {
     let mut a = 1;
-    let mut c = Point{ x:1, y:0 };
+    let mut c = Point { x: 1, y: 0 };
 
     // Captured by value, but variable is dead on entry.
     (move || {
-        // This will not trigger a warning for unused variable as
-        // c.x will be treated as a Non-tracked place
-        c.x = 1;
+        c.x = 1; //~ WARN value captured by `c.x` is never read
         println!("{}", c.x);
         a = 1; //~ WARN value captured by `a` is never read
         println!("{}", a);
@@ -27,10 +25,10 @@ pub fn f() {
 
     // Read and written to, but never actually used.
     (move || {
-        // This will not trigger a warning for unused variable as
-        // c.x will be treated as a Non-tracked place
-        c.x += 1;
-        a += 1; //~ WARN unused variable: `a`
+        c.x += 1; //~  WARN value captured by `c.x` is never read
+                  //~| WARN value assigned to `c.x` is never read
+        a += 1; //~  WARN value captured by `a` is never read
+                //~| WARN value assigned to `a` is never read
     })();
 
     (move || {
@@ -45,10 +43,7 @@ pub fn f() {
     let b = Box::new(42);
     (move || {
         println!("{}", c.x);
-        // Never read because this is FnOnce closure.
-        // This will not trigger a warning for unused variable as
-        // c.x will be treated as a Non-tracked place
-        c.x += 1;
+        c.x += 1; //~ WARN value assigned to `c.x` is never read
         println!("{}", a);
         a += 1; //~ WARN value assigned to `a` is never read
         drop(b);
@@ -56,35 +51,32 @@ pub fn f() {
 }
 
 #[derive(Debug)]
-struct MyStruct<'a>  {
-    x: Option<& 'a str>,
+struct MyStruct<'a> {
+    x: Option<&'a str>,
     y: i32,
 }
 
 pub fn nested() {
-    let mut a : Option<& str>;
+    let mut a: Option<&str>;
     a = None;
-    let mut b : Option<& str>;
+    let mut b: Option<&str>;
     b = None;
-    let mut d = MyStruct{ x: None, y: 1};
-    let mut e = MyStruct{ x: None, y: 1};
+    let mut d = MyStruct { x: None, y: 1 };
+    let mut e = MyStruct { x: None, y: 1 };
     (|| {
         (|| {
-            // This will not trigger a warning for unused variable as
-            // d.x will be treated as a Non-tracked place
-            d.x = Some("d1");
+            d.x = Some("d1"); //~ WARN value assigned to `d.x` is never read
             d.x = Some("d2");
             a = Some("d1"); //~ WARN value assigned to `a` is never read
             a = Some("d2");
         })();
         (move || {
-            // This will not trigger a warning for unused variable as
-            //e.x will be treated as a Non-tracked place
-            e.x = Some("e1");
-            e.x = Some("e2");
-            b = Some("e1"); //~ WARN value assigned to `b` is never read
-                            //~| WARN unused variable: `b`
-            b = Some("e2"); //~ WARN value assigned to `b` is never read
+            e.x = Some("e1"); //~  WARN value captured by `e.x` is never read
+                              //~| WARN value assigned to `e.x` is never read
+            e.x = Some("e2"); //~  WARN value assigned to `e.x` is never read
+            b = Some("e1"); //~  WARN value captured by `b` is never read
+                            //~| WARN value assigned to `b` is never read
+            b = Some("e2"); //~  WARN value assigned to `b` is never read
         })();
     })();
 }

tests/ui/closures/2229_closure_analysis/diagnostics/liveness.stderr

@@ -1,10 +1,10 @@
-warning: value captured by `a` is never read
-  --> $DIR/liveness.rs:24:9
+warning: value assigned to `c.x` is never read
+  --> $DIR/liveness.rs:46:9
    |
-LL |         a = 1;
-   |         ^
+LL |         c.x += 1;
+   |         ^^^^^^^^
    |
-   = help: did you mean to capture by reference instead?
+   = help: maybe it is overwritten before being read?
 note: the lint level is defined here
   --> $DIR/liveness.rs:5:9
    |
@@ -12,54 +12,125 @@ LL | #![warn(unused)]
    |         ^^^^^^
    = note: `#[warn(unused_assignments)]` implied by `#[warn(unused)]`
 
-warning: unused variable: `a`
-  --> $DIR/liveness.rs:33:9
+warning: value assigned to `a` is never read
+  --> $DIR/liveness.rs:48:9
+   |
+LL |         a += 1;
+   |         ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value captured by `c.x` is never read
+  --> $DIR/liveness.rs:28:9
+   |
+LL |         c.x += 1;
+   |         ^^^
+   |
+   = help: did you mean to capture by reference instead?
+
+warning: value assigned to `c.x` is never read
+  --> $DIR/liveness.rs:28:9
+   |
+LL |         c.x += 1;
+   |         ^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value captured by `a` is never read
+  --> $DIR/liveness.rs:30:9
    |
 LL |         a += 1;
    |         ^
    |
    = help: did you mean to capture by reference instead?
-   = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
 
 warning: value assigned to `a` is never read
-  --> $DIR/liveness.rs:53:9
+  --> $DIR/liveness.rs:30:9
    |
 LL |         a += 1;
-   |         ^
+   |         ^^^^^^
    |
    = help: maybe it is overwritten before being read?
 
-warning: value assigned to `a` is never read
+warning: value captured by `c.x` is never read
+  --> $DIR/liveness.rs:20:9
+   |
+LL |         c.x = 1;
+   |         ^^^
+   |
+   = help: did you mean to capture by reference instead?
+
+warning: value captured by `a` is never read
+  --> $DIR/liveness.rs:22:9
+   |
+LL |         a = 1;
+   |         ^
+   |
+   = help: did you mean to capture by reference instead?
+
+warning: value captured by `e.x` is never read
+  --> $DIR/liveness.rs:74:13
+   |
+LL |             e.x = Some("e1");
+   |             ^^^
+   |
+   = help: did you mean to capture by reference instead?
+
+warning: value assigned to `e.x` is never read
+  --> $DIR/liveness.rs:74:13
+   |
+LL |             e.x = Some("e1");
+   |             ^^^^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `e.x` is never read
+  --> $DIR/liveness.rs:76:13
+   |
+LL |             e.x = Some("e2");
+   |             ^^^^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value captured by `b` is never read
   --> $DIR/liveness.rs:77:13
    |
-LL |             a = Some("d1");
-   |             ^
-   |
-   = help: maybe it is overwritten before being read?
-
-warning: value assigned to `b` is never read
-  --> $DIR/liveness.rs:85:13
-   |
-LL |             b = Some("e1");
-   |             ^
-   |
-   = help: maybe it is overwritten before being read?
-
-warning: value assigned to `b` is never read
-  --> $DIR/liveness.rs:87:13
-   |
-LL |             b = Some("e2");
-   |             ^
-   |
-   = help: maybe it is overwritten before being read?
-
-warning: unused variable: `b`
-  --> $DIR/liveness.rs:85:13
-   |
 LL |             b = Some("e1");
    |             ^
    |
    = help: did you mean to capture by reference instead?
 
-warning: 7 warnings emitted
+warning: value assigned to `b` is never read
+  --> $DIR/liveness.rs:77:13
+   |
+LL |             b = Some("e1");
+   |             ^^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `b` is never read
+  --> $DIR/liveness.rs:79:13
+   |
+LL |             b = Some("e2");
+   |             ^^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `d.x` is never read
+  --> $DIR/liveness.rs:68:13
+   |
+LL |             d.x = Some("d1");
+   |             ^^^^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `a` is never read
+  --> $DIR/liveness.rs:70:13
+   |
+LL |             a = Some("d1");
+   |             ^^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: 16 warnings emitted
 

tests/ui/closures/2229_closure_analysis/diagnostics/liveness_unintentional_copy.rs

@@ -12,14 +12,16 @@ struct MyStruct {
 
 pub fn unintentional_copy_one() {
     let mut a = 1;
-    let mut last = MyStruct{ a: 1, b: 1};
+    //~^ WARN unused variable: `a`
+    let mut last = MyStruct { a: 1, b: 1 };
+    //~^ WARN unused variable: `last`
     let mut f = move |s| {
-        // This will not trigger a warning for unused variable
-        // as last.a will be treated as a Non-tracked place
         last.a = s;
+        //~^ WARN value captured by `last.a` is never read
+        //~| WARN value assigned to `last.a` is never read
         a = s;
-        //~^ WARN value assigned to `a` is never read
-        //~| WARN unused variable: `a`
+        //~^ WARN value captured by `a` is never read
+        //~| WARN value assigned to `a` is never read
     };
     f(2);
     f(3);
@@ -28,12 +30,16 @@ pub fn unintentional_copy_one() {
 
 pub fn unintentional_copy_two() {
     let mut a = 1;
-    let mut sum = MyStruct{ a: 1, b: 0};
+    //~^ WARN unused variable: `a`
+    let mut sum = MyStruct { a: 1, b: 0 };
+    //~^ WARN unused variable: `sum`
     (1..10).for_each(move |x| {
-        // This will not trigger a warning for unused variable
-        // as sum.b will be treated as a Non-tracked place
         sum.b += x;
-        a += x; //~ WARN unused variable: `a`
+        //~^ WARN value captured by `sum.b` is never read
+        //~| WARN value assigned to `sum.b` is never read
+        a += x;
+        //~^ WARN value captured by `a` is never read
+        //~| WARN value assigned to `a` is never read
     });
 }
 

tests/ui/closures/2229_closure_analysis/diagnostics/liveness_unintentional_copy.stderr

@@ -1,10 +1,10 @@
-warning: value assigned to `a` is never read
-  --> $DIR/liveness_unintentional_copy.rs:20:9
+warning: value captured by `last.a` is never read
+  --> $DIR/liveness_unintentional_copy.rs:19:9
    |
-LL |         a = s;
-   |         ^
+LL |         last.a = s;
+   |         ^^^^^^
    |
-   = help: maybe it is overwritten before being read?
+   = help: did you mean to capture by reference instead?
 note: the lint level is defined here
   --> $DIR/liveness_unintentional_copy.rs:4:9
    |
@@ -12,22 +12,87 @@ LL | #![warn(unused)]
    |         ^^^^^^
    = note: `#[warn(unused_assignments)]` implied by `#[warn(unused)]`
 
-warning: unused variable: `a`
-  --> $DIR/liveness_unintentional_copy.rs:20:9
+warning: value assigned to `last.a` is never read
+  --> $DIR/liveness_unintentional_copy.rs:19:9
+   |
+LL |         last.a = s;
+   |         ^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value captured by `a` is never read
+  --> $DIR/liveness_unintentional_copy.rs:22:9
    |
 LL |         a = s;
    |         ^
    |
    = help: did you mean to capture by reference instead?
-   = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
+
+warning: value assigned to `a` is never read
+  --> $DIR/liveness_unintentional_copy.rs:22:9
+   |
+LL |         a = s;
+   |         ^^^^^
+   |
+   = help: maybe it is overwritten before being read?
 
 warning: unused variable: `a`
-  --> $DIR/liveness_unintentional_copy.rs:36:9
+  --> $DIR/liveness_unintentional_copy.rs:14:9
+   |
+LL |     let mut a = 1;
+   |         ^^^^^ help: if this is intentional, prefix it with an underscore: `_a`
+   |
+   = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
+
+warning: unused variable: `last`
+  --> $DIR/liveness_unintentional_copy.rs:16:9
+   |
+LL |     let mut last = MyStruct { a: 1, b: 1 };
+   |         ^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_last`
+
+warning: value captured by `sum.b` is never read
+  --> $DIR/liveness_unintentional_copy.rs:37:9
+   |
+LL |         sum.b += x;
+   |         ^^^^^
+   |
+   = help: did you mean to capture by reference instead?
+
+warning: value assigned to `sum.b` is never read
+  --> $DIR/liveness_unintentional_copy.rs:37:9
+   |
+LL |         sum.b += x;
+   |         ^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value captured by `a` is never read
+  --> $DIR/liveness_unintentional_copy.rs:40:9
    |
 LL |         a += x;
    |         ^
    |
    = help: did you mean to capture by reference instead?
 
-warning: 3 warnings emitted
+warning: value assigned to `a` is never read
+  --> $DIR/liveness_unintentional_copy.rs:40:9
+   |
+LL |         a += x;
+   |         ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: unused variable: `a`
+  --> $DIR/liveness_unintentional_copy.rs:32:9
+   |
+LL |     let mut a = 1;
+   |         ^^^^^ help: if this is intentional, prefix it with an underscore: `_a`
+
+warning: unused variable: `sum`
+  --> $DIR/liveness_unintentional_copy.rs:34:9
+   |
+LL |     let mut sum = MyStruct { a: 1, b: 0 };
+   |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_sum`
+
+warning: 12 warnings emitted
 

tests/ui/closures/2229_closure_analysis/run_pass/destructure-pattern-closure-within-closure.stderr

@@ -1,8 +1,8 @@
-warning: unused variable: `g2`
-  --> $DIR/destructure-pattern-closure-within-closure.rs:10:17
+warning: unused variable: `t2`
+  --> $DIR/destructure-pattern-closure-within-closure.rs:13:21
    |
-LL |         let (_, g2) = g;
-   |                 ^^ help: if this is intentional, prefix it with an underscore: `_g2`
+LL |             let (_, t2) = t;
+   |                     ^^ help: if this is intentional, prefix it with an underscore: `_t2`
    |
 note: the lint level is defined here
   --> $DIR/destructure-pattern-closure-within-closure.rs:3:9
@@ -11,11 +11,11 @@ LL | #![warn(unused)]
    |         ^^^^^^
    = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
 
-warning: unused variable: `t2`
-  --> $DIR/destructure-pattern-closure-within-closure.rs:13:21
+warning: unused variable: `g2`
+  --> $DIR/destructure-pattern-closure-within-closure.rs:10:17
    |
-LL |             let (_, t2) = t;
-   |                     ^^ help: if this is intentional, prefix it with an underscore: `_t2`
+LL |         let (_, g2) = g;
+   |                 ^^ help: if this is intentional, prefix it with an underscore: `_g2`
 
 warning: 2 warnings emitted
 

tests/ui/closures/moved-upvar-mut-rebind-11958.rs

@@ -7,7 +7,8 @@
 
 pub fn main() {
     let mut x = 1;
+    //~^ WARN unused variable: `x`
     let _thunk = Box::new(move|| { x = 2; });
-    //~^ WARN value assigned to `x` is never read
-    //~| WARN unused variable: `x`
+    //~^ WARN value captured by `x` is never read
+    //~| WARN value assigned to `x` is never read
 }

tests/ui/closures/moved-upvar-mut-rebind-11958.stderr

@@ -1,20 +1,27 @@
-warning: value assigned to `x` is never read
-  --> $DIR/moved-upvar-mut-rebind-11958.rs:10:36
-   |
-LL |     let _thunk = Box::new(move|| { x = 2; });
-   |                                    ^
-   |
-   = help: maybe it is overwritten before being read?
-   = note: `#[warn(unused_assignments)]` (part of `#[warn(unused)]`) on by default
-
-warning: unused variable: `x`
-  --> $DIR/moved-upvar-mut-rebind-11958.rs:10:36
+warning: value captured by `x` is never read
+  --> $DIR/moved-upvar-mut-rebind-11958.rs:11:36
    |
 LL |     let _thunk = Box::new(move|| { x = 2; });
    |                                    ^
    |
    = help: did you mean to capture by reference instead?
+   = note: `#[warn(unused_assignments)]` (part of `#[warn(unused)]`) on by default
+
+warning: value assigned to `x` is never read
+  --> $DIR/moved-upvar-mut-rebind-11958.rs:11:36
+   |
+LL |     let _thunk = Box::new(move|| { x = 2; });
+   |                                    ^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: unused variable: `x`
+  --> $DIR/moved-upvar-mut-rebind-11958.rs:9:9
+   |
+LL |     let mut x = 1;
+   |         ^^^^^ help: if this is intentional, prefix it with an underscore: `_x`
+   |
    = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default
 
-warning: 2 warnings emitted
+warning: 3 warnings emitted
 

tests/ui/const-generics/defaults/trait_object_lt_defaults.rs

@@ -1,6 +1,6 @@
 //@ aux-build:trait_object_lt_defaults_lib.rs
 //@ run-pass
-#![allow(dead_code)]
+#![allow(dead_code, unused)]
 extern crate trait_object_lt_defaults_lib;
 
 // Tests that `A<'a, 3, dyn Test>` is short for `A<'a, 3, dyn Test + 'a>`

tests/ui/drop/or-pattern-drop-order.rs

@@ -25,7 +25,7 @@ fn assert_drop_order(expected_drops: impl IntoIterator<Item = u32>, f: impl Fn(&
     assert_eq!(order, correct_order);
 }
 
-#[expect(unused_variables, unused_assignments, irrefutable_let_patterns)]
+#[expect(unused_variables, irrefutable_let_patterns)]
 fn main() {
     // When bindings are declared with `let pat;`, they're visited in left-to-right order, using the
     // order given by the first occurrence of each variable. They're later dropped in reverse.

tests/ui/dropck/dropck-empty-array.rs

@@ -1,6 +1,7 @@
 //@ run-pass
 
-#[allow(dead_code)]
+#![allow(dead_code, unused_variables, unused_assignments)]
+
 struct Struct<'s>(&'s str);
 
 impl<'s> Drop for Struct<'s> {

tests/ui/enum-discriminant/issue-46519.rs

@@ -7,6 +7,7 @@
 #[should_panic(expected = "creating inhabited type")]
 fn test() {
     FontLanguageOverride::system_font(SystemFont::new());
+    //~^ WARNING unreachable expression
 }
 
 pub enum FontLanguageOverride {

tests/ui/enum-discriminant/issue-46519.stderr

@@ -0,0 +1,18 @@
+warning: unreachable expression
+  --> $DIR/issue-46519.rs:9:5
+   |
+LL |     FontLanguageOverride::system_font(SystemFont::new());
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-----------------^
+   |     |                                 |
+   |     |                                 any code following this expression is unreachable
+   |     unreachable expression
+   |
+note: this expression has type `SystemFont`, which is uninhabited
+  --> $DIR/issue-46519.rs:9:39
+   |
+LL |     FontLanguageOverride::system_font(SystemFont::new());
+   |                                       ^^^^^^^^^^^^^^^^^
+   = note: `#[warn(unreachable_code)]` (part of `#[warn(unused)]`) on by default
+
+warning: 1 warning emitted
+

tests/ui/fn/mut-arg-of-borrowed-type-meant-to-be-arg-of-mut-borrow.stderr

@@ -14,25 +14,6 @@ LL |    let object2 = Object;
 LL ~    *object = object2;
    |
 
-error: value assigned to `object` is never read
-  --> $DIR/mut-arg-of-borrowed-type-meant-to-be-arg-of-mut-borrow.rs:14:4
-   |
-LL |    object = &object2;
-   |    ^^^^^^
-   |
-note: the lint level is defined here
-  --> $DIR/mut-arg-of-borrowed-type-meant-to-be-arg-of-mut-borrow.rs:2:9
-   |
-LL | #![deny(unused_assignments)]
-   |         ^^^^^^^^^^^^^^^^^^
-help: you might have meant to mutate the pointed at value being passed in, instead of changing the reference in the local binding
-   |
-LL ~ fn change_object2(object: &mut Object) {
-LL |
-LL |    let object2 = Object;
-LL ~    *object = object2;
-   |
-
 error[E0597]: `object2` does not live long enough
   --> $DIR/mut-arg-of-borrowed-type-meant-to-be-arg-of-mut-borrow.rs:14:13
    |
@@ -51,17 +32,22 @@ LL | }
    | - `object2` dropped here while still borrowed
 
 error: value assigned to `object` is never read
-  --> $DIR/mut-arg-of-borrowed-type-meant-to-be-arg-of-mut-borrow.rs:22:5
+  --> $DIR/mut-arg-of-borrowed-type-meant-to-be-arg-of-mut-borrow.rs:14:4
    |
-LL |     object = &mut object2;
-   |     ^^^^^^
+LL |    object = &object2;
+   |    ^^^^^^^^^^^^^^^^^
    |
+note: the lint level is defined here
+  --> $DIR/mut-arg-of-borrowed-type-meant-to-be-arg-of-mut-borrow.rs:2:9
+   |
+LL | #![deny(unused_assignments)]
+   |         ^^^^^^^^^^^^^^^^^^
 help: you might have meant to mutate the pointed at value being passed in, instead of changing the reference in the local binding
    |
-LL ~ fn change_object3(object: &mut Object) {
+LL ~ fn change_object2(object: &mut Object) {
 LL |
-LL |     let object2 = Object;
-LL ~     *object = object2;
+LL |    let object2 = Object;
+LL ~    *object = object2;
    |
 
 error[E0596]: cannot borrow `object2` as mutable, as it is not declared as mutable
@@ -75,6 +61,20 @@ help: consider changing this to be mutable
 LL |     let mut object2 = Object;
    |         +++
 
+error: value assigned to `object` is never read
+  --> $DIR/mut-arg-of-borrowed-type-meant-to-be-arg-of-mut-borrow.rs:22:5
+   |
+LL |     object = &mut object2;
+   |     ^^^^^^^^^^^^^^^^^^^^^
+   |
+help: you might have meant to mutate the pointed at value being passed in, instead of changing the reference in the local binding
+   |
+LL ~ fn change_object3(object: &mut Object) {
+LL |
+LL |     let object2 = Object;
+LL ~     *object = object2;
+   |
+
 error: aborting due to 5 previous errors
 
 Some errors have detailed explanations: E0308, E0596, E0597.

tests/ui/intrinsics/panic-uninitialized-zeroed.rs

@@ -7,7 +7,7 @@
 //@ ignore-backends: gcc
 //@ edition:2024
 
-#![allow(deprecated, invalid_value)]
+#![allow(deprecated, invalid_value, unreachable_code)]
 #![feature(never_type, rustc_private)]
 
 use std::{

tests/ui/issues/issue-19367.rs

@@ -1,4 +1,7 @@
 //@ run-pass
+
+#![allow(unused_assignments)]
+
 struct S {
     o: Option<String>
 }

tests/ui/lint/dead-code/issue-85071-2.rs

@@ -17,6 +17,6 @@ fn main() {
     let s = S;
     let x = s.f();
     //~^ WARNING: unused variable: `x`
+    //~| WARNING: unreachable definition
     let _y = x;
-    //~^ WARNING: unreachable definition
 }

tests/ui/lint/dead-code/issue-85071-2.stderr

@@ -1,11 +1,10 @@
 warning: unreachable definition
-  --> $DIR/issue-85071-2.rs:20:9
+  --> $DIR/issue-85071-2.rs:18:9
    |
 LL |     let x = s.f();
-   |             ----- any code following this expression is unreachable
-LL |
-LL |     let _y = x;
-   |         ^^ unreachable definition
+   |         ^   ----- any code following this expression is unreachable
+   |         |
+   |         unreachable definition
    |
 note: this expression has type `Foo`, which is uninhabited
   --> $DIR/issue-85071-2.rs:18:13

tests/ui/lint/dead-code/issue-85071.rs

@@ -14,6 +14,6 @@ fn f() -> Foo {todo!()}
 fn main() {
     let x = f();
     //~^ WARNING: unused variable: `x`
+    //~| WARNING: unreachable definition
     let _ = x;
-    //~^ WARNING: unreachable expression
 }

tests/ui/lint/dead-code/issue-85071.stderr

@@ -1,11 +1,10 @@
-warning: unreachable expression
-  --> $DIR/issue-85071.rs:17:13
+warning: unreachable definition
+  --> $DIR/issue-85071.rs:15:9
    |
 LL |     let x = f();
-   |             --- any code following this expression is unreachable
-LL |
-LL |     let _ = x;
-   |             ^ unreachable expression
+   |         ^   --- any code following this expression is unreachable
+   |         |
+   |         unreachable definition
    |
 note: this expression has type `Foo`, which is uninhabited
   --> $DIR/issue-85071.rs:15:13

tests/ui/lint/future-incompat-json-test.stderr

@@ -1,4 +1,4 @@
-{"$message_type":"future_incompat","future_incompat_report":[{"diagnostic":{"$message_type":"diagnostic","message":"unused variable: `x`","code":{"code":"unused_variables","explanation":null},"level":"warning","spans":[{"file_name":"$DIR/future-incompat-json-test.rs","byte_start":340,"byte_end":341,"line_start":9,"line_end":9,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"    let x = 1;","highlight_start":9,"highlight_end":10}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"if this is intentional, prefix it with an underscore","code":null,"level":"help","spans":[{"file_name":"$DIR/future-incompat-json-test.rs","byte_start":340,"byte_end":341,"line_start":9,"line_end":9,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"    let x = 1;","highlight_start":9,"highlight_end":10}],"label":null,"suggested_replacement":"_x","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"warning: unused variable: `x`
+{"$message_type":"future_incompat","future_incompat_report":[{"diagnostic":{"$message_type":"diagnostic","message":"unused variable: `x`","code":{"code":"unused_variables","explanation":null},"level":"warning","spans":[{"file_name":"$DIR/future-incompat-json-test.rs","byte_start":340,"byte_end":341,"line_start":9,"line_end":9,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"    let x = 1;","highlight_start":9,"highlight_end":10}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"if this is intentional, prefix it with an underscore","code":null,"level":"help","spans":[{"file_name":"$DIR/future-incompat-json-test.rs","byte_start":340,"byte_end":341,"line_start":9,"line_end":9,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"    let x = 1;","highlight_start":9,"highlight_end":10}],"label":null,"suggested_replacement":"_x","suggestion_applicability":"MachineApplicable","expansion":null}],"children":[],"rendered":null}],"rendered":"warning: unused variable: `x`
   --> $DIR/future-incompat-json-test.rs:9:9
    |
 LL |     let x = 1;

tests/ui/lint/issue-49588-non-shorthand-field-patterns-in-pattern-macro.rs

@@ -13,4 +13,5 @@ macro_rules! pat {
 
 fn main() {
     let pat!(value) = Value { value: () };
+    //~^ WARN value assigned to `value` is never read
 }

tests/ui/lint/issue-49588-non-shorthand-field-patterns-in-pattern-macro.stderr

@@ -0,0 +1,11 @@
+warning: value assigned to `value` is never read
+  --> $DIR/issue-49588-non-shorthand-field-patterns-in-pattern-macro.rs:15:14
+   |
+LL |     let pat!(value) = Value { value: () };
+   |              ^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+   = note: `#[warn(unused_assignments)]` (part of `#[warn(unused)]`) on by default
+
+warning: 1 warning emitted
+

tests/ui/lint/non-snake-case/lint-uppercase-variables.stderr

@@ -24,14 +24,14 @@ note: the lint level is defined here
 LL | #![warn(unused)]
    |         ^^^^^^
    = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
-help: if this is intentional, prefix it with an underscore
-   |
-LL |         _Foo => {}
-   |         +
 help: you might have meant to pattern match on the similarly named variant `Foo`
    |
 LL |         foo::Foo::Foo => {}
    |         ++++++++++
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         _Foo => {}
+   |         +
 
 warning: unused variable: `Foo`
   --> $DIR/lint-uppercase-variables.rs:28:9
@@ -39,14 +39,14 @@ warning: unused variable: `Foo`
 LL |     let Foo = foo::Foo::Foo;
    |         ^^^
    |
-help: if this is intentional, prefix it with an underscore
-   |
-LL |     let _Foo = foo::Foo::Foo;
-   |         +
 help: you might have meant to pattern match on the similarly named variant `Foo`
    |
 LL |     let foo::Foo::Foo = foo::Foo::Foo;
    |         ++++++++++
+help: if this is intentional, prefix it with an underscore
+   |
+LL |     let _Foo = foo::Foo::Foo;
+   |         +
 
 error[E0170]: pattern binding `Foo` is named the same as one of the variants of the type `foo::Foo`
   --> $DIR/lint-uppercase-variables.rs:33:17

tests/ui/lint/rfc-2383-lint-reason/expect_lint_from_macro.stderr

@@ -2,11 +2,19 @@ warning: unused variable: `x`
   --> $DIR/expect_lint_from_macro.rs:7:13
    |
 LL |         let x = 0;
-   |             ^ help: if this is intentional, prefix it with an underscore: `_x`
+   |             ^
 ...
 LL |     trigger_unused_variables_macro!();
    |     --------------------------------- in this macro invocation
    |
+help: `x` is captured in macro and introduced a unused variable
+  --> $DIR/expect_lint_from_macro.rs:7:13
+   |
+LL |         let x = 0;
+   |             ^
+...
+LL |     trigger_unused_variables_macro!();
+   |     --------------------------------- in this macro invocation
 note: the lint level is defined here
   --> $DIR/expect_lint_from_macro.rs:3:9
    |
@@ -18,11 +26,19 @@ warning: unused variable: `x`
   --> $DIR/expect_lint_from_macro.rs:7:13
    |
 LL |         let x = 0;
-   |             ^ help: if this is intentional, prefix it with an underscore: `_x`
+   |             ^
 ...
 LL |     trigger_unused_variables_macro!();
    |     --------------------------------- in this macro invocation
    |
+help: `x` is captured in macro and introduced a unused variable
+  --> $DIR/expect_lint_from_macro.rs:7:13
+   |
+LL |         let x = 0;
+   |             ^
+...
+LL |     trigger_unused_variables_macro!();
+   |     --------------------------------- in this macro invocation
    = note: this warning originates in the macro `trigger_unused_variables_macro` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 warning: 2 warnings emitted

tests/ui/lint/rfc-2383-lint-reason/force_warn_expected_lints_fulfilled.stderr

@@ -14,12 +14,6 @@ LL |     let x = 2;
    |
    = note: requested on the command line with `--force-warn unused-variables`
 
-warning: unused variable: `fox_name`
-  --> $DIR/force_warn_expected_lints_fulfilled.rs:26:9
-   |
-LL |     let fox_name = "Sir Nibbles";
-   |         ^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_fox_name`
-
 warning: variable does not need to be mutable
   --> $DIR/force_warn_expected_lints_fulfilled.rs:30:9
    |
@@ -30,6 +24,12 @@ LL |     let mut what_does_the_fox_say = "*ding* *deng* *dung*";
    |
    = note: requested on the command line with `--force-warn unused-mut`
 
+warning: unused variable: `fox_name`
+  --> $DIR/force_warn_expected_lints_fulfilled.rs:26:9
+   |
+LL |     let fox_name = "Sir Nibbles";
+   |         ^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_fox_name`
+
 warning: unused variable: `this_should_fulfill_the_expectation`
   --> $DIR/force_warn_expected_lints_fulfilled.rs:41:9
    |

tests/ui/lint/unused/issue-117284-arg-in-macro.rs

@@ -1,7 +1,7 @@
 #![deny(unused_variables)]
 macro_rules! make_var {
     ($struct:ident, $var:ident) => {
-        let $var = $struct.$var;
+        let $var = $struct.$var; //~ ERROR unused variable: `var`
     };
 }
 
@@ -12,6 +12,6 @@ struct MyStruct {
 
 fn main() {
     let s = MyStruct { var: 42 };
-    make_var!(s, var); //~ ERROR unused variable: `var`
+    make_var!(s, var);
     let a = 1; //~ ERROR unused variable: `a`
 }

tests/ui/lint/unused/issue-117284-arg-in-macro.stderr

@@ -1,8 +1,11 @@
 error: unused variable: `var`
-  --> $DIR/issue-117284-arg-in-macro.rs:15:18
+  --> $DIR/issue-117284-arg-in-macro.rs:4:13
    |
+LL |         let $var = $struct.$var;
+   |             ^^^^
+...
 LL |     make_var!(s, var);
-   |                  ^^^
+   |     ----------------- in this macro invocation
    |
 help: `var` is captured in macro and introduced a unused variable
   --> $DIR/issue-117284-arg-in-macro.rs:4:13

tests/ui/lint/unused/issue-47390-unused-variable-in-struct-pattern.stderr

@@ -1,27 +1,45 @@
-warning: unused variable: `i_think_continually`
-  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:26:9
+warning: variable does not need to be mutable
+  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:33:9
    |
-LL |     let i_think_continually = 2;
-   |         ^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_i_think_continually`
+LL |     let mut mut_unused_var = 1;
+   |         ----^^^^^^^^^^^^^^
+   |         |
+   |         help: remove this `mut`
    |
 note: the lint level is defined here
   --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:5:9
    |
 LL | #![warn(unused)] // UI tests pass `-A unused` (#43896)
    |         ^^^^^^
+   = note: `#[warn(unused_mut)]` implied by `#[warn(unused)]`
+
+warning: variable does not need to be mutable
+  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:37:10
+   |
+LL |     let (mut var, unused_var) = (1, 2);
+   |          ----^^^
+   |          |
+   |          help: remove this `mut`
+
+warning: unused variable: `i_think_continually`
+  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:26:9
+   |
+LL |     let i_think_continually = 2;
+   |         ^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_i_think_continually`
+   |
    = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
 
 warning: unused variable: `mut_unused_var`
-  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:33:13
+  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:33:9
    |
 LL |     let mut mut_unused_var = 1;
-   |             ^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_mut_unused_var`
+   |         ^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_mut_unused_var`
 
 warning: unused variable: `var`
-  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:37:14
+  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:37:10
    |
 LL |     let (mut var, unused_var) = (1, 2);
-   |              ^^^ help: if this is intentional, prefix it with an underscore: `_var`
+   |          ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_var`
 
 warning: unused variable: `unused_var`
   --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:37:19
@@ -36,22 +54,13 @@ LL |     if let SoulHistory { corridors_of_light,
    |                          ^^^^^^^^^^^^^^^^^^ help: try ignoring the field: `corridors_of_light: _`
 
 warning: variable `hours_are_suns` is assigned to, but never used
-  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:46:30
+  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:46:26
    |
 LL |                          mut hours_are_suns,
-   |                              ^^^^^^^^^^^^^^
+   |                          ^^^^^^^^^^^^^^^^^^
    |
    = note: consider using `_hours_are_suns` instead
 
-warning: value assigned to `hours_are_suns` is never read
-  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:48:9
-   |
-LL |         hours_are_suns = false;
-   |         ^^^^^^^^^^^^^^
-   |
-   = help: maybe it is overwritten before being read?
-   = note: `#[warn(unused_assignments)]` implied by `#[warn(unused)]`
-
 warning: unused variable: `fire`
   --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:52:32
    |
@@ -94,23 +103,14 @@ warning: unused variable: `case`
 LL |         Tuple(Large::Suit { case }, ()) => {}
    |                             ^^^^ help: try ignoring the field: `case: _`
 
-warning: variable does not need to be mutable
-  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:33:9
+warning: value assigned to `hours_are_suns` is never read
+  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:48:9
    |
-LL |     let mut mut_unused_var = 1;
-   |         ----^^^^^^^^^^^^^^
-   |         |
-   |         help: remove this `mut`
+LL |         hours_are_suns = false;
+   |         ^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: `#[warn(unused_mut)]` implied by `#[warn(unused)]`
-
-warning: variable does not need to be mutable
-  --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:37:10
-   |
-LL |     let (mut var, unused_var) = (1, 2);
-   |          ----^^^
-   |          |
-   |          help: remove this `mut`
+   = help: maybe it is overwritten before being read?
+   = note: `#[warn(unused_assignments)]` implied by `#[warn(unused)]`
 
 warning: 16 warnings emitted
 

tests/ui/lint/unused/issue-54180-unused-ref-field.stderr

@@ -11,6 +11,12 @@ LL | #![deny(unused)]
    |         ^^^^^^
    = note: `#[deny(unused_variables)]` implied by `#[deny(unused)]`
 
+error: unused variable: `x`
+  --> $DIR/issue-54180-unused-ref-field.rs:29:45
+   |
+LL |     let _: i32 = points.iter().map(|Point { x, y }| y).sum();
+   |                                             ^ help: try ignoring the field: `x: _`
+
 error: unused variable: `f1`
   --> $DIR/issue-54180-unused-ref-field.rs:26:13
    |
@@ -23,11 +29,5 @@ error: unused variable: `x`
 LL |         Point { y, ref mut x } => y,
    |                    ^^^^^^^^^ help: try ignoring the field: `x: _`
 
-error: unused variable: `x`
-  --> $DIR/issue-54180-unused-ref-field.rs:29:45
-   |
-LL |     let _: i32 = points.iter().map(|Point { x, y }| y).sum();
-   |                                             ^ help: try ignoring the field: `x: _`
-
 error: aborting due to 4 previous errors
 

tests/ui/lint/unused/lint-unused-variables.stderr

@@ -10,24 +10,18 @@ note: the lint level is defined here
 LL | #![deny(unused_variables)]
    |         ^^^^^^^^^^^^^^^^
 
-error: unused variable: `a`
-  --> $DIR/lint-unused-variables.rs:21:9
-   |
-LL |         a: i32,
-   |         ^ help: if this is intentional, prefix it with an underscore: `_a`
-
-error: unused variable: `a`
-  --> $DIR/lint-unused-variables.rs:67:9
-   |
-LL |         a: i32,
-   |         ^ help: if this is intentional, prefix it with an underscore: `_a`
-
 error: unused variable: `b`
   --> $DIR/lint-unused-variables.rs:13:5
    |
 LL |     b: i32,
    |     ^ help: if this is intentional, prefix it with an underscore: `_b`
 
+error: unused variable: `a`
+  --> $DIR/lint-unused-variables.rs:21:9
+   |
+LL |         a: i32,
+   |         ^ help: if this is intentional, prefix it with an underscore: `_a`
+
 error: unused variable: `b`
   --> $DIR/lint-unused-variables.rs:28:9
    |
@@ -70,5 +64,11 @@ error: unused variable: `b`
 LL |         b: i32,
    |         ^ help: if this is intentional, prefix it with an underscore: `_b`
 
+error: unused variable: `a`
+  --> $DIR/lint-unused-variables.rs:67:9
+   |
+LL |         a: i32,
+   |         ^ help: if this is intentional, prefix it with an underscore: `_a`
+
 error: aborting due to 11 previous errors
 

tests/ui/liveness/liveness-asm.stderr

@@ -1,8 +1,8 @@
 warning: value assigned to `src` is never read
-  --> $DIR/liveness-asm.rs:14:32
+  --> $DIR/liveness-asm.rs:14:5
    |
 LL |     asm!("/*{0}*/", inout(reg) src);
-   |                                ^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: maybe it is overwritten before being read?
 note: the lint level is defined here
@@ -12,10 +12,10 @@ LL | #![warn(unused_assignments)]
    |         ^^^^^^^^^^^^^^^^^^
 
 warning: value assigned to `src` is never read
-  --> $DIR/liveness-asm.rs:24:39
+  --> $DIR/liveness-asm.rs:24:5
    |
 LL |     asm!("/*{0}*/", inout(reg) src => src);
-   |                                       ^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: maybe it is overwritten before being read?
 

tests/ui/liveness/liveness-consts.rs

@@ -4,16 +4,18 @@
 
 pub static A: i32 = {
     let mut i = 0;
-    let mut a = 0; //~ WARN variable `a` is assigned to, but never used
+    let mut a = 0;
+    //~^ WARN variable `a` is assigned to, but never used
     while i < 10 {
         i += 1;
         a += 1;
+        //~^ WARN value assigned to `a` is never read
     }
     i
 };
 
 pub const B: u32 = {
-    let mut b = 1;
+    let mut b = 1; //~ WARN value assigned to `b` is never read
     b += 1; //~ WARN value assigned to `b` is never read
     b = 42;
     b

tests/ui/liveness/liveness-consts.stderr

@@ -1,5 +1,5 @@
 warning: unused variable: `e`
-  --> $DIR/liveness-consts.rs:24:13
+  --> $DIR/liveness-consts.rs:26:13
    |
 LL |         let e = 1;
    |             ^ help: if this is intentional, prefix it with an underscore: `_e`
@@ -12,53 +12,69 @@ LL | #![warn(unused)]
    = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
 
 warning: unused variable: `s`
-  --> $DIR/liveness-consts.rs:33:24
+  --> $DIR/liveness-consts.rs:35:24
    |
 LL | pub fn f(x: [u8; { let s = 17; 100 }]) -> [u8;  { let z = 18; 100 }] {
    |                        ^ help: if this is intentional, prefix it with an underscore: `_s`
 
 warning: unused variable: `z`
-  --> $DIR/liveness-consts.rs:33:55
+  --> $DIR/liveness-consts.rs:35:55
    |
 LL | pub fn f(x: [u8; { let s = 17; 100 }]) -> [u8;  { let z = 18; 100 }] {
    |                                                       ^ help: if this is intentional, prefix it with an underscore: `_z`
 
 warning: variable `a` is assigned to, but never used
-  --> $DIR/liveness-consts.rs:7:13
+  --> $DIR/liveness-consts.rs:7:9
    |
 LL |     let mut a = 0;
-   |             ^
+   |         ^^^^^
    |
    = note: consider using `_a` instead
 
-warning: value assigned to `b` is never read
-  --> $DIR/liveness-consts.rs:17:5
+warning: value assigned to `a` is never read
+  --> $DIR/liveness-consts.rs:11:9
    |
-LL |     b += 1;
-   |     ^
+LL |         a += 1;
+   |         ^^^^^^
    |
    = help: maybe it is overwritten before being read?
    = note: `#[warn(unused_assignments)]` implied by `#[warn(unused)]`
 
+warning: value assigned to `b` is never read
+  --> $DIR/liveness-consts.rs:18:17
+   |
+LL |     let mut b = 1;
+   |                 ^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `b` is never read
+  --> $DIR/liveness-consts.rs:19:5
+   |
+LL |     b += 1;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
 warning: unused variable: `z`
-  --> $DIR/liveness-consts.rs:60:13
+  --> $DIR/liveness-consts.rs:62:13
    |
 LL |         let z = 42;
    |             ^ help: if this is intentional, prefix it with an underscore: `_z`
 
 warning: value assigned to `t` is never read
-  --> $DIR/liveness-consts.rs:42:9
+  --> $DIR/liveness-consts.rs:44:9
    |
 LL |         t = t + t;
-   |         ^
+   |         ^^^^^^^^^
    |
    = help: maybe it is overwritten before being read?
 
 warning: unused variable: `w`
-  --> $DIR/liveness-consts.rs:49:13
+  --> $DIR/liveness-consts.rs:51:13
    |
 LL |         let w = 10;
    |             ^ help: if this is intentional, prefix it with an underscore: `_w`
 
-warning: 8 warnings emitted
+warning: 10 warnings emitted
 

tests/ui/liveness/liveness-dead.stderr

@@ -1,8 +1,8 @@
 error: value assigned to `x` is never read
-  --> $DIR/liveness-dead.rs:9:13
+  --> $DIR/liveness-dead.rs:9:24
    |
 LL |     let mut x: isize = 3;
-   |             ^
+   |                        ^
    |
    = help: maybe it is overwritten before being read?
 note: the lint level is defined here
@@ -15,15 +15,15 @@ error: value assigned to `x` is never read
   --> $DIR/liveness-dead.rs:17:5
    |
 LL |     x = 4;
-   |     ^
+   |     ^^^^^
    |
    = help: maybe it is overwritten before being read?
 
 error: value passed to `x` is never read
-  --> $DIR/liveness-dead.rs:20:11
+  --> $DIR/liveness-dead.rs:20:7
    |
 LL | fn f4(mut x: i32) {
-   |           ^
+   |       ^^^^^
    |
    = help: maybe it is overwritten before being read?
 
@@ -31,7 +31,7 @@ error: value assigned to `x` is never read
   --> $DIR/liveness-dead.rs:27:5
    |
 LL |     x = 4;
-   |     ^
+   |     ^^^^^
    |
    = help: maybe it is overwritten before being read?
 

tests/ui/liveness/liveness-unused.rs

@@ -39,6 +39,7 @@ fn f3b() {
     //~^ ERROR variable `z` is assigned to, but never used
     loop {
         z += 4;
+        //~^ ERROR value assigned to `z` is never read
     }
 }
 
@@ -46,6 +47,7 @@ fn f3b() {
 fn f3c() {
     let mut z = 3;
     loop { z += 4; }
+    //~^ ERROR value assigned to `z` is never read
 }
 
 #[allow(unused_variables)]
@@ -55,6 +57,16 @@ fn f3d() {
     x += 4;
 }
 
+fn f3e() {
+    let a = 13;
+    let mut z = 3;
+    //~^ ERROR variable `z` is assigned to, but never used
+    loop {
+        z += a;
+        //~^ ERROR value assigned to `z` is never read
+    }
+}
+
 fn f4() {
     match Some(3) {
       Some(i) => {
@@ -68,7 +80,15 @@ enum tri {
     a(isize), b(isize), c(isize)
 }
 
-fn f4b() -> isize {
+fn f4b() {
+    match tri::a(3) {
+      tri::a(i) | tri::b(i) | tri::c(i) => {
+          //~^ ERROR unused variable: `i`
+      }
+    }
+}
+
+fn f4c() -> isize {
     match tri::a(3) {
       tri::a(i) | tri::b(i) | tri::c(i) => {
         i
@@ -76,6 +96,13 @@ fn f4b() -> isize {
     }
 }
 
+fn f4d() {
+    match tri::a(3) {
+      tri::a(i) | tri::b(i) | tri::c(i) if i == 0 => {}
+      _ => {}
+    }
+}
+
 fn f5a() {
     for x in 1..10 { }
     //~^ ERROR unused variable: `x`
@@ -138,10 +165,92 @@ fn f7() {
     drop(a);
 }
 
+fn f8(a: u32) {
+    let _ = a;
+}
+
+fn f9() {
+    let mut a = 10;
+    //~^ ERROR variable `a` is assigned to, but never used
+    let b = 13;
+    let c = 13;
+    let d = 13;
+    let e = 13;
+    let f = 13;
+    let g = 13;
+    let h = 13;
+
+    a += b;
+    //~^ ERROR value assigned to `a` is never read
+    a -= c;
+    //~^ ERROR value assigned to `a` is never read
+    a *= d;
+    //~^ ERROR value assigned to `a` is never read
+    a /= e;
+    //~^ ERROR value assigned to `a` is never read
+    a |= f;
+    //~^ ERROR value assigned to `a` is never read
+    a &= g;
+    //~^ ERROR value assigned to `a` is never read
+    a %= h;
+    //~^ ERROR value assigned to `a` is never read
+}
+
+fn f9b() {
+    let mut a = 10;
+    let b = 13;
+    let c = 13;
+    let d = 13;
+    let e = 13;
+    let f = 13;
+    let g = 13;
+    let h = 13;
+
+    a += b;
+    a -= c;
+    a *= d;
+    a /= e;
+    a |= f;
+    a &= g;
+    a %= h;
+
+    let _ = a;
+}
+
+fn f9c() {
+    let mut a = 10.;
+    //~^ ERROR variable `a` is assigned to, but never used
+    let b = 13.;
+    let c = 13.;
+    let d = 13.;
+    let e = 13.;
+    let f = 13.;
+
+    a += b;
+    //~^ ERROR value assigned to `a` is never read
+    a -= c;
+    //~^ ERROR value assigned to `a` is never read
+    a *= d;
+    //~^ ERROR value assigned to `a` is never read
+    a /= e;
+    //~^ ERROR value assigned to `a` is never read
+    a %= f;
+    //~^ ERROR value assigned to `a` is never read
+}
+
+fn f10<T>(mut a: T, b: T) {
+    //~^ ERROR variable `a` is assigned to, but never used
+    a = b;
+    //~^ ERROR value assigned to `a` is never read
+}
+
+fn f10b<T>(mut a: Box<T>, b: Box<T>) {
+    a = b;
+}
+
 // unused params warnings are not needed for intrinsic functions without bodies
 #[rustc_intrinsic]
 unsafe fn simd_shuffle<T, I, U>(a: T, b: T, i: I) -> U;
 
-
 fn main() {
 }

tests/ui/liveness/liveness-unused.stderr

@@ -1,5 +1,5 @@
 warning: unreachable statement
-  --> $DIR/liveness-unused.rs:93:9
+  --> $DIR/liveness-unused.rs:120:9
    |
 LL |         continue;
    |         -------- any code following this expression is unreachable
@@ -44,10 +44,10 @@ LL |     let x = 3;
    |         ^ help: if this is intentional, prefix it with an underscore: `_x`
 
 error: variable `x` is assigned to, but never used
-  --> $DIR/liveness-unused.rs:31:13
+  --> $DIR/liveness-unused.rs:31:9
    |
 LL |     let mut x = 3;
-   |             ^
+   |         ^^^^^
    |
    = note: consider using `_x` instead
 
@@ -55,7 +55,7 @@ error: value assigned to `x` is never read
   --> $DIR/liveness-unused.rs:33:5
    |
 LL |     x += 4;
-   |     ^
+   |     ^^^^^^
    |
    = help: maybe it is overwritten before being read?
 note: the lint level is defined here
@@ -65,39 +65,82 @@ LL | #![deny(unused_assignments)]
    |         ^^^^^^^^^^^^^^^^^^
 
 error: variable `z` is assigned to, but never used
-  --> $DIR/liveness-unused.rs:38:13
+  --> $DIR/liveness-unused.rs:38:9
    |
 LL |     let mut z = 3;
-   |             ^
+   |         ^^^^^
    |
    = note: consider using `_z` instead
 
+error: value assigned to `z` is never read
+  --> $DIR/liveness-unused.rs:41:9
+   |
+LL |         z += 4;
+   |         ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `z` is never read
+  --> $DIR/liveness-unused.rs:49:12
+   |
+LL |     loop { z += 4; }
+   |            ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: variable `z` is assigned to, but never used
+  --> $DIR/liveness-unused.rs:62:9
+   |
+LL |     let mut z = 3;
+   |         ^^^^^
+   |
+   = note: consider using `_z` instead
+
+error: value assigned to `z` is never read
+  --> $DIR/liveness-unused.rs:65:9
+   |
+LL |         z += a;
+   |         ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
 error: unused variable: `i`
-  --> $DIR/liveness-unused.rs:60:12
+  --> $DIR/liveness-unused.rs:72:12
    |
 LL |       Some(i) => {
    |            ^ help: if this is intentional, prefix it with an underscore: `_i`
 
+error: unused variable: `i`
+  --> $DIR/liveness-unused.rs:85:14
+   |
+LL |       tri::a(i) | tri::b(i) | tri::c(i) => {
+   |              ^           ^           ^
+   |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |       tri::a(_i) | tri::b(_i) | tri::c(_i) => {
+   |              +            +            +
+
 error: unused variable: `x`
-  --> $DIR/liveness-unused.rs:80:9
+  --> $DIR/liveness-unused.rs:107:9
    |
 LL |     for x in 1..10 { }
    |         ^ help: if this is intentional, prefix it with an underscore: `_x`
 
 error: unused variable: `x`
-  --> $DIR/liveness-unused.rs:85:10
+  --> $DIR/liveness-unused.rs:112:10
    |
 LL |     for (x, _) in [1, 2, 3].iter().enumerate() { }
    |          ^ help: if this is intentional, prefix it with an underscore: `_x`
 
 error: unused variable: `x`
-  --> $DIR/liveness-unused.rs:90:13
+  --> $DIR/liveness-unused.rs:117:13
    |
 LL |     for (_, x) in [1, 2, 3].iter().enumerate() {
    |             ^ help: if this is intentional, prefix it with an underscore: `_x`
 
 error: variable `x` is assigned to, but never used
-  --> $DIR/liveness-unused.rs:113:9
+  --> $DIR/liveness-unused.rs:140:9
    |
 LL |     let x;
    |         ^
@@ -105,12 +148,140 @@ LL |     let x;
    = note: consider using `_x` instead
 
 error: value assigned to `x` is never read
-  --> $DIR/liveness-unused.rs:117:9
+  --> $DIR/liveness-unused.rs:144:9
    |
 LL |         x = 0;
-   |         ^
+   |         ^^^^^
    |
    = help: maybe it is overwritten before being read?
 
-error: aborting due to 13 previous errors; 1 warning emitted
+error: variable `a` is assigned to, but never used
+  --> $DIR/liveness-unused.rs:173:9
+   |
+LL |     let mut a = 10;
+   |         ^^^^^
+   |
+   = note: consider using `_a` instead
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:183:5
+   |
+LL |     a += b;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:185:5
+   |
+LL |     a -= c;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:187:5
+   |
+LL |     a *= d;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:189:5
+   |
+LL |     a /= e;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:191:5
+   |
+LL |     a |= f;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:193:5
+   |
+LL |     a &= g;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:195:5
+   |
+LL |     a %= h;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: variable `a` is assigned to, but never used
+  --> $DIR/liveness-unused.rs:221:9
+   |
+LL |     let mut a = 10.;
+   |         ^^^^^
+   |
+   = note: consider using `_a` instead
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:229:5
+   |
+LL |     a += b;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:231:5
+   |
+LL |     a -= c;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:233:5
+   |
+LL |     a *= d;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:235:5
+   |
+LL |     a /= e;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:237:5
+   |
+LL |     a %= f;
+   |     ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: variable `a` is assigned to, but never used
+  --> $DIR/liveness-unused.rs:241:11
+   |
+LL | fn f10<T>(mut a: T, b: T) {
+   |           ^^^^^
+   |
+   = note: consider using `_a` instead
+
+error: value assigned to `a` is never read
+  --> $DIR/liveness-unused.rs:243:5
+   |
+LL |     a = b;
+   |     ^
+   |
+   = help: maybe it is overwritten before being read?
+
+error: aborting due to 34 previous errors; 1 warning emitted
 

tests/ui/liveness/liveness-upvars.rs

@@ -7,8 +7,8 @@
 pub fn unintentional_copy_one() {
     let mut last = None;
     let mut f = move |s| {
-        last = Some(s); //~  WARN value assigned to `last` is never read
-                        //~| WARN unused variable: `last`
+        last = Some(s); //~  WARN value captured by `last` is never read
+                        //~| WARN value assigned to `last` is never read
     };
     f("a");
     f("b");
@@ -19,7 +19,9 @@ pub fn unintentional_copy_one() {
 pub fn unintentional_copy_two() {
     let mut sum = 0;
     (1..10).for_each(move |x| {
-        sum += x; //~ WARN unused variable: `sum`
+        sum += x;
+        //~^ WARN value captured by `sum` is never read
+        //~| WARN value assigned to `sum` is never read
     });
     dbg!(sum);
 }
@@ -39,11 +41,14 @@ pub fn f() {
 
     // Read and written to, but never actually used.
     let _ = move || {
-        c += 1; //~ WARN unused variable: `c`
+        c += 1;
+        //~^ WARN value captured by `c` is never read
+        //~|  WARN value assigned to `c` is never read
     };
     let _ = async move {
-        c += 1; //~  WARN value assigned to `c` is never read
-                //~| WARN unused variable: `c`
+        c += 1;
+        //~^ WARN value captured by `c` is never read
+        //~|  WARN value assigned to `c` is never read
     };
 
     let _ = move || {
@@ -74,8 +79,8 @@ pub fn nested() {
             d = Some("d2");
         };
         let _ = move || {
-            e = Some("e1"); //~  WARN value assigned to `e` is never read
-                            //~| WARN unused variable: `e`
+            e = Some("e1"); //~  WARN value captured by `e` is never read
+                            //~| WARN value assigned to `e` is never read
             e = Some("e2"); //~  WARN value assigned to `e` is never read
         };
     };
@@ -84,7 +89,8 @@ pub fn nested() {
 pub fn g<T: Default>(mut v: T) {
     let _ = |r| {
         if r {
-            v = T::default(); //~ WARN value assigned to `v` is never read
+            v = T::default();
+            //~^ WARN value assigned to `v` is never read
         } else {
             drop(v);
         }
@@ -96,8 +102,8 @@ pub fn h<T: Copy + Default + std::fmt::Debug>() {
     let _ = move |b| {
         loop {
             if b {
-                z = T::default(); //~  WARN value assigned to `z` is never read
-                                  //~| WARN unused variable: `z`
+                z = T::default(); //~  WARN value captured by `z` is never read
+                                  //~| WARN value assigned to `z` is never read
             } else {
                 return;
             }
@@ -123,7 +129,7 @@ pub fn async_coroutine() {
 
     let _ = async move {
         state = 4;  //~  WARN value assigned to `state` is never read
-                    //~| WARN unused variable: `state`
+                    //~| WARN value captured by `state` is never read
         yield_now().await;
         state = 5;  //~ WARN value assigned to `state` is never read
     };
@@ -141,4 +147,21 @@ pub fn coroutine() {
     };
 }
 
+pub fn panics() {
+    use std::panic::{AssertUnwindSafe, catch_unwind, resume_unwind};
+
+    let mut panic = true;
+
+    // `a` can be called again, even if it has panicked at an earlier run.
+    let mut a = || {
+        if panic {
+            panic = false;
+            resume_unwind(Box::new(()))
+        }
+    };
+
+    catch_unwind(AssertUnwindSafe(|| a())).ok();
+    a();
+}
+
 fn main() {}

tests/ui/liveness/liveness-upvars.stderr

@@ -1,10 +1,10 @@
-warning: value assigned to `last` is never read
+warning: value captured by `last` is never read
   --> $DIR/liveness-upvars.rs:10:9
    |
 LL |         last = Some(s);
    |         ^^^^
    |
-   = help: maybe it is overwritten before being read?
+   = help: did you mean to capture by reference instead?
 note: the lint level is defined here
   --> $DIR/liveness-upvars.rs:4:9
    |
@@ -12,16 +12,15 @@ LL | #![warn(unused)]
    |         ^^^^^^
    = note: `#[warn(unused_assignments)]` implied by `#[warn(unused)]`
 
-warning: unused variable: `last`
+warning: value assigned to `last` is never read
   --> $DIR/liveness-upvars.rs:10:9
    |
 LL |         last = Some(s);
-   |         ^^^^
+   |         ^^^^^^^^^^^^^^
    |
-   = help: did you mean to capture by reference instead?
-   = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
+   = help: maybe it is overwritten before being read?
 
-warning: unused variable: `sum`
+warning: value captured by `sum` is never read
   --> $DIR/liveness-upvars.rs:22:9
    |
 LL |         sum += x;
@@ -29,8 +28,64 @@ LL |         sum += x;
    |
    = help: did you mean to capture by reference instead?
 
+warning: value assigned to `sum` is never read
+  --> $DIR/liveness-upvars.rs:22:9
+   |
+LL |         sum += x;
+   |         ^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `c` is never read
+  --> $DIR/liveness-upvars.rs:69:9
+   |
+LL |         c += 1;
+   |         ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `c` is never read
+  --> $DIR/liveness-upvars.rs:63:9
+   |
+LL |         c += 1;
+   |         ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
 warning: value captured by `c` is never read
-  --> $DIR/liveness-upvars.rs:32:9
+  --> $DIR/liveness-upvars.rs:49:9
+   |
+LL |         c += 1;
+   |         ^
+   |
+   = help: did you mean to capture by reference instead?
+
+warning: value assigned to `c` is never read
+  --> $DIR/liveness-upvars.rs:49:9
+   |
+LL |         c += 1;
+   |         ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value captured by `c` is never read
+  --> $DIR/liveness-upvars.rs:44:9
+   |
+LL |         c += 1;
+   |         ^
+   |
+   = help: did you mean to capture by reference instead?
+
+warning: value assigned to `c` is never read
+  --> $DIR/liveness-upvars.rs:44:9
+   |
+LL |         c += 1;
+   |         ^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value captured by `c` is never read
+  --> $DIR/liveness-upvars.rs:38:9
    |
 LL |         c = 1;
    |         ^
@@ -38,148 +93,108 @@ LL |         c = 1;
    = help: did you mean to capture by reference instead?
 
 warning: value captured by `c` is never read
-  --> $DIR/liveness-upvars.rs:36:9
+  --> $DIR/liveness-upvars.rs:34:9
    |
 LL |         c = 1;
    |         ^
    |
    = help: did you mean to capture by reference instead?
 
-warning: unused variable: `c`
-  --> $DIR/liveness-upvars.rs:42:9
+warning: value captured by `e` is never read
+  --> $DIR/liveness-upvars.rs:82:13
    |
-LL |         c += 1;
-   |         ^
+LL |             e = Some("e1");
+   |             ^
    |
    = help: did you mean to capture by reference instead?
 
-warning: value assigned to `c` is never read
-  --> $DIR/liveness-upvars.rs:45:9
+warning: value assigned to `e` is never read
+  --> $DIR/liveness-upvars.rs:82:13
    |
-LL |         c += 1;
-   |         ^
+LL |             e = Some("e1");
+   |             ^^^^^^^^^^^^^^
    |
    = help: maybe it is overwritten before being read?
 
-warning: unused variable: `c`
-  --> $DIR/liveness-upvars.rs:45:9
+warning: value assigned to `e` is never read
+  --> $DIR/liveness-upvars.rs:84:13
    |
-LL |         c += 1;
-   |         ^
-   |
-   = help: did you mean to capture by reference instead?
-
-warning: value assigned to `c` is never read
-  --> $DIR/liveness-upvars.rs:58:9
-   |
-LL |         c += 1;
-   |         ^
-   |
-   = help: maybe it is overwritten before being read?
-
-warning: value assigned to `c` is never read
-  --> $DIR/liveness-upvars.rs:64:9
-   |
-LL |         c += 1;
-   |         ^
+LL |             e = Some("e2");
+   |             ^^^^^^^^^^^^^^
    |
    = help: maybe it is overwritten before being read?
 
 warning: value assigned to `d` is never read
-  --> $DIR/liveness-upvars.rs:73:13
+  --> $DIR/liveness-upvars.rs:78:13
    |
 LL |             d = Some("d1");
-   |             ^
+   |             ^^^^^^^^^^^^^^
    |
    = help: maybe it is overwritten before being read?
 
-warning: value assigned to `e` is never read
-  --> $DIR/liveness-upvars.rs:77:13
-   |
-LL |             e = Some("e1");
-   |             ^
-   |
-   = help: maybe it is overwritten before being read?
-
-warning: value assigned to `e` is never read
-  --> $DIR/liveness-upvars.rs:79:13
-   |
-LL |             e = Some("e2");
-   |             ^
-   |
-   = help: maybe it is overwritten before being read?
-
-warning: unused variable: `e`
-  --> $DIR/liveness-upvars.rs:77:13
-   |
-LL |             e = Some("e1");
-   |             ^
-   |
-   = help: did you mean to capture by reference instead?
-
 warning: value assigned to `v` is never read
-  --> $DIR/liveness-upvars.rs:87:13
+  --> $DIR/liveness-upvars.rs:92:13
    |
 LL |             v = T::default();
    |             ^
    |
    = help: maybe it is overwritten before being read?
 
-warning: value assigned to `z` is never read
-  --> $DIR/liveness-upvars.rs:99:17
-   |
-LL |                 z = T::default();
-   |                 ^
-   |
-   = help: maybe it is overwritten before being read?
-
-warning: unused variable: `z`
-  --> $DIR/liveness-upvars.rs:99:17
+warning: value captured by `z` is never read
+  --> $DIR/liveness-upvars.rs:105:17
    |
 LL |                 z = T::default();
    |                 ^
    |
    = help: did you mean to capture by reference instead?
 
-warning: value assigned to `state` is never read
-  --> $DIR/liveness-upvars.rs:125:9
+warning: value assigned to `z` is never read
+  --> $DIR/liveness-upvars.rs:105:17
+   |
+LL |                 z = T::default();
+   |                 ^^^^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value captured by `state` is never read
+  --> $DIR/liveness-upvars.rs:131:9
    |
 LL |         state = 4;
    |         ^^^^^
    |
+   = help: did you mean to capture by reference instead?
+
+warning: value assigned to `state` is never read
+  --> $DIR/liveness-upvars.rs:131:9
+   |
+LL |         state = 4;
+   |         ^^^^^^^^^
+   |
    = help: maybe it is overwritten before being read?
 
 warning: value assigned to `state` is never read
-  --> $DIR/liveness-upvars.rs:128:9
+  --> $DIR/liveness-upvars.rs:134:9
    |
 LL |         state = 5;
-   |         ^^^^^
+   |         ^^^^^^^^^
    |
    = help: maybe it is overwritten before being read?
 
-warning: unused variable: `state`
-  --> $DIR/liveness-upvars.rs:125:9
-   |
-LL |         state = 4;
-   |         ^^^^^
-   |
-   = help: did you mean to capture by reference instead?
-
 warning: value assigned to `s` is never read
-  --> $DIR/liveness-upvars.rs:137:9
+  --> $DIR/liveness-upvars.rs:143:9
    |
 LL |         s = 1;
-   |         ^
+   |         ^^^^^
    |
    = help: maybe it is overwritten before being read?
 
 warning: value assigned to `s` is never read
-  --> $DIR/liveness-upvars.rs:139:9
+  --> $DIR/liveness-upvars.rs:145:9
    |
 LL |         s = yield ();
-   |         ^
+   |         ^^^^^^^^^^^^
    |
    = help: maybe it is overwritten before being read?
 
-warning: 22 warnings emitted
+warning: 24 warnings emitted
 

tests/ui/object-lifetime/object-lifetime-default-default-to-static.rs

@@ -3,7 +3,7 @@
 // fields and fn arguments.
 
 
-#![allow(dead_code)]
+#![allow(dead_code, unused)]
 
 trait Test {
     fn foo(&self) { }

tests/ui/object-lifetime/object-lifetime-default-from-ref-struct.rs

@@ -3,7 +3,7 @@
 // lifetime bound.
 
 
-#![allow(dead_code)]
+#![allow(dead_code, unused)]
 
 use std::fmt::Display;
 

tests/ui/object-lifetime/object-lifetime-default-from-rptr-box.rs

@@ -3,7 +3,7 @@
 // through the `Box` struct.
 
 
-#![allow(dead_code)]
+#![allow(dead_code, unused)]
 
 trait Test {
     fn foo(&self) { }

tests/ui/object-lifetime/object-lifetime-default-from-rptr-mut.rs

@@ -3,7 +3,7 @@
 // lifetime bound.
 
 
-#![allow(dead_code)]
+#![allow(dead_code, unused)]
 
 trait Test {
     fn foo(&self) { }

tests/ui/object-lifetime/object-lifetime-default-from-rptr-struct.rs

@@ -3,7 +3,7 @@
 // through the `MyBox` struct.
 
 
-#![allow(dead_code)]
+#![allow(dead_code, unused)]
 
 trait Test {
     fn foo(&self) { }

tests/ui/object-lifetime/object-lifetime-default-from-rptr.rs

@@ -3,7 +3,7 @@
 // lifetime bound.
 
 
-#![allow(dead_code)]
+#![allow(dead_code, unused)]
 
 use std::fmt::Display;
 

tests/ui/object-lifetime/object-lifetime-default-inferred.rs

@@ -3,7 +3,7 @@
 // valid.
 
 
-#![allow(dead_code)]
+#![allow(dead_code, unused)]
 
 trait Test {
     fn foo(&self) { }

tests/ui/or-patterns/binding-typo-2.rs

@@ -16,8 +16,8 @@ fn foo(x: (Lol, Lol)) {
         //~| HELP: you might have meant to use the similarly named previously used binding `Bar`
         //~| NOTE: pattern doesn't bind `Ban`
         //~| NOTE: variable not in all patterns
-        //~| ERROR: variable `Ban` is assigned to, but never used
-        //~| NOTE: consider using `_Ban` instead
+        //~| ERROR: unused variable: `Ban`
+        //~| HELP: if this is intentional, prefix it with an underscore
         //~| HELP: you might have meant to pattern match on the similarly named
         _ => {}
     }
@@ -27,8 +27,8 @@ fn foo(x: (Lol, Lol)) {
         //~| HELP: you might have meant to use the similarly named unit variant `Bar`
         //~| NOTE: pattern doesn't bind `Ban`
         //~| NOTE: variable not in all patterns
-        //~| ERROR: variable `Ban` is assigned to, but never used
-        //~| NOTE: consider using `_Ban` instead
+        //~| ERROR: unused variable: `Ban`
+        //~| HELP: if this is intentional, prefix it with an underscore
         //~| HELP: you might have meant to pattern match on the similarly named
         _ => {}
     }
@@ -73,8 +73,8 @@ fn bar(x: (Lol, Lol)) {
         //~| HELP: you might have meant to use the similarly named constant `Bat`
         //~| NOTE: pattern doesn't bind `Ban`
         //~| NOTE: variable not in all patterns
-        //~| ERROR: variable `Ban` is assigned to, but never used
-        //~| NOTE: consider using `_Ban` instead
+        //~| ERROR: unused variable: `Ban`
+        //~| HELP: if this is intentional, prefix it with an underscore
         //~| HELP: you might have meant to pattern match on the similarly named
         _ => {}
     }
@@ -89,8 +89,8 @@ fn baz(x: (Lol, Lol)) {
         //~| HELP: you might have meant to use the similarly named constant `Bat`
         //~| NOTE: pattern doesn't bind `Ban`
         //~| NOTE: variable not in all patterns
-        //~| ERROR: variable `Ban` is assigned to, but never used
-        //~| NOTE: consider using `_Ban` instead
+        //~| ERROR: unused variable: `Ban`
+        //~| HELP: if this is intentional, prefix it with an underscore
         //~| HELP: you might have meant to pattern match on the similarly named
         _ => {}
     }

tests/ui/or-patterns/binding-typo-2.stderr

@@ -97,13 +97,12 @@ LL -         (Foo, _) | (Ban, Foo) => {}
 LL +         (Foo, _) | (Bat, Foo) => {}
    |
 
-error: variable `Ban` is assigned to, but never used
+error: unused variable: `Ban`
   --> $DIR/binding-typo-2.rs:14:23
    |
 LL |         (Foo, Bar) | (Ban, Foo) => {}
    |                       ^^^
    |
-   = note: consider using `_Ban` instead
 note: the lint level is defined here
   --> $DIR/binding-typo-2.rs:2:9
    |
@@ -114,19 +113,26 @@ help: you might have meant to pattern match on the similarly named variant `Bar`
 LL -         (Foo, Bar) | (Ban, Foo) => {}
 LL +         (Foo, Bar) | (Lol::Bar, Foo) => {}
    |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         (Foo, Bar) | (_Ban, Foo) => {}
+   |                       +
 
-error: variable `Ban` is assigned to, but never used
+error: unused variable: `Ban`
   --> $DIR/binding-typo-2.rs:25:21
    |
 LL |         (Foo, _) | (Ban, Foo) => {}
    |                     ^^^
    |
-   = note: consider using `_Ban` instead
 help: you might have meant to pattern match on the similarly named variant `Bar`
    |
 LL -         (Foo, _) | (Ban, Foo) => {}
 LL +         (Foo, _) | (Lol::Bar, Foo) => {}
    |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         (Foo, _) | (_Ban, Foo) => {}
+   |                     +
 
 error: unused variable: `Non`
   --> $DIR/binding-typo-2.rs:37:9
@@ -134,15 +140,15 @@ error: unused variable: `Non`
 LL |         Non => {}
    |         ^^^
    |
-help: if this is intentional, prefix it with an underscore
-   |
-LL |         _Non => {}
-   |         +
 help: you might have meant to pattern match on the similarly named variant `None`
    |
 LL -         Non => {}
 LL +         std::prelude::v1::None => {}
    |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         _Non => {}
+   |         +
 
 error: unused variable: `Non`
   --> $DIR/binding-typo-2.rs:44:9
@@ -150,15 +156,15 @@ error: unused variable: `Non`
 LL |         Non | None => {}
    |         ^^^
    |
-help: if this is intentional, prefix it with an underscore
-   |
-LL |         _Non | None => {}
-   |         +
 help: you might have meant to pattern match on the similarly named variant `None`
    |
 LL -         Non | None => {}
 LL +         std::prelude::v1::None | None => {}
    |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         _Non | None => {}
+   |         +
 
 error: unused variable: `Non`
   --> $DIR/binding-typo-2.rs:54:9
@@ -166,41 +172,47 @@ error: unused variable: `Non`
 LL |         Non | Some(_) => {}
    |         ^^^
    |
-help: if this is intentional, prefix it with an underscore
-   |
-LL |         _Non | Some(_) => {}
-   |         +
 help: you might have meant to pattern match on the similarly named variant `None`
    |
 LL -         Non | Some(_) => {}
 LL +         std::prelude::v1::None | Some(_) => {}
    |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         _Non | Some(_) => {}
+   |         +
 
-error: variable `Ban` is assigned to, but never used
+error: unused variable: `Ban`
   --> $DIR/binding-typo-2.rs:69:21
    |
 LL |         (Foo, _) | (Ban, Foo) => {}
    |                     ^^^
    |
-   = note: consider using `_Ban` instead
 help: you might have meant to pattern match on the similarly named variant `Bar`
    |
 LL -         (Foo, _) | (Ban, Foo) => {}
 LL +         (Foo, _) | (Lol::Bar, Foo) => {}
    |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         (Foo, _) | (_Ban, Foo) => {}
+   |                     +
 
-error: variable `Ban` is assigned to, but never used
+error: unused variable: `Ban`
   --> $DIR/binding-typo-2.rs:86:21
    |
 LL |         (Foo, _) | (Ban, Foo) => {}
    |                     ^^^
    |
-   = note: consider using `_Ban` instead
 help: you might have meant to pattern match on the similarly named variant `Bar`
    |
 LL -         (Foo, _) | (Ban, Foo) => {}
 LL +         (Foo, _) | (Lol::Bar, Foo) => {}
    |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         (Foo, _) | (_Ban, Foo) => {}
+   |                     +
 
 error: unused variable: `Ban`
   --> $DIR/binding-typo-2.rs:98:10
@@ -208,15 +220,15 @@ error: unused variable: `Ban`
 LL |         (Ban, _) => {}
    |          ^^^
    |
-help: if this is intentional, prefix it with an underscore
-   |
-LL |         (_Ban, _) => {}
-   |          +
 help: you might have meant to pattern match on the similarly named variant `Bar`
    |
 LL -         (Ban, _) => {}
 LL +         (Lol::Bar, _) => {}
    |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         (_Ban, _) => {}
+   |          +
 
 error: unused variable: `Ban`
   --> $DIR/binding-typo-2.rs:104:9
@@ -224,15 +236,15 @@ error: unused variable: `Ban`
 LL |         Ban => {}
    |         ^^^
    |
-help: if this is intentional, prefix it with an underscore
-   |
-LL |         _Ban => {}
-   |         +
 help: you might have meant to pattern match on the similarly named struct `Bay`
    |
 LL -         Ban => {}
 LL +         Bay => {}
    |
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         _Ban => {}
+   |         +
 
 error: unused variable: `Batery`
   --> $DIR/binding-typo-2.rs:110:9
@@ -240,14 +252,14 @@ error: unused variable: `Batery`
 LL |         Batery => {}
    |         ^^^^^^
    |
-help: if this is intentional, prefix it with an underscore
-   |
-LL |         _Batery => {}
-   |         +
 help: you might have meant to pattern match on the similarly named constant `Battery`
    |
 LL |         Battery => {}
    |            +
+help: if this is intentional, prefix it with an underscore
+   |
+LL |         _Batery => {}
+   |         +
 
 error: aborting due to 16 previous errors
 

tests/ui/packed/packed-struct-drop-aligned.rs

@@ -1,6 +1,8 @@
 //@ run-pass
 #![feature(coroutines, stmt_expr_attributes)]
 #![feature(coroutine_trait)]
+#![allow(unused_assignments, unused_variables)]
+
 use std::cell::Cell;
 use std::mem;
 use std::ops::Coroutine;

tests/ui/parser/intersection-patterns-1.fixed

@@ -9,6 +9,7 @@
 //@ run-rustfix
 
 #![allow(unused_variables)]
+#![allow(unused_assignments)]
 
 fn main() {
     let s: Option<u8> = None;

tests/ui/parser/intersection-patterns-1.rs

@@ -9,6 +9,7 @@
 //@ run-rustfix
 
 #![allow(unused_variables)]
+#![allow(unused_assignments)]
 
 fn main() {
     let s: Option<u8> = None;

tests/ui/parser/intersection-patterns-1.stderr

@@ -1,5 +1,5 @@
 error: pattern on wrong side of `@`
-  --> $DIR/intersection-patterns-1.rs:17:9
+  --> $DIR/intersection-patterns-1.rs:18:9
    |
 LL |         Some(x) @ y => {}
    |         -------^^^-
@@ -14,7 +14,7 @@ LL +         y @ Some(x) => {}
    |
 
 error: pattern on wrong side of `@`
-  --> $DIR/intersection-patterns-1.rs:27:9
+  --> $DIR/intersection-patterns-1.rs:28:9
    |
 LL |         1 ..= 5 @ e => {}
    |         -------^^^-

tests/ui/pattern/bindings-after-at/bind-by-copy.rs

@@ -1,5 +1,6 @@
 //@ run-pass
 #![allow(unused)]
+#![warn(unused_assignments)]
 
 // Test copy
 
@@ -34,10 +35,12 @@ pub fn main() {
     let mut x@B {b, ..} = B {a: 10, b: C {c: 20}};
     assert_eq!(x.a, 10);
     x.b.c = 30;
+    //~^ WARN value assigned to `x` is never read
     assert_eq!(b.c, 20);
     let mut y@D {d, ..} = D {a: 10, d: C {c: 20}};
     assert_eq!(y.a, 10);
     y.d.c = 30;
+    //~^ WARN value assigned to `y` is never read
     assert_eq!(d.c, 20);
 
     match (E::E { a: 10, e: C { c: 20 } }) {
@@ -50,7 +53,9 @@ pub fn main() {
     }
     match (E::E { a: 10, e: C { c: 20 } }) {
         mut x @ E::E{ a, e: C { mut c } } => {
+            //~^ WARN value assigned to `a` is never read
             x = E::NotE;
+            //~^ WARN value assigned to `x` is never read
             c += 30;
             assert_eq!(c, 50);
         }

tests/ui/pattern/bindings-after-at/bind-by-copy.stderr

@@ -0,0 +1,39 @@
+warning: value assigned to `x` is never read
+  --> $DIR/bind-by-copy.rs:37:5
+   |
+LL |     x.b.c = 30;
+   |     ^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+note: the lint level is defined here
+  --> $DIR/bind-by-copy.rs:3:9
+   |
+LL | #![warn(unused_assignments)]
+   |         ^^^^^^^^^^^^^^^^^^
+
+warning: value assigned to `y` is never read
+  --> $DIR/bind-by-copy.rs:42:5
+   |
+LL |     y.d.c = 30;
+   |     ^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `x` is never read
+  --> $DIR/bind-by-copy.rs:57:13
+   |
+LL |             x = E::NotE;
+   |             ^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `a` is never read
+  --> $DIR/bind-by-copy.rs:55:23
+   |
+LL |         mut x @ E::E{ a, e: C { mut c } } => {
+   |                       ^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: 4 warnings emitted
+

tests/ui/return/early-return-with-unreachable-code-24353.rs

@@ -4,6 +4,7 @@ fn main() {
     return ();
 
     let x = ();
+    //~^ WARN unused variable: `x`
     x
 }
 

tests/ui/return/early-return-with-unreachable-code-24353.stderr

@@ -0,0 +1,10 @@
+warning: unused variable: `x`
+  --> $DIR/early-return-with-unreachable-code-24353.rs:6:9
+   |
+LL |     let x = ();
+   |         ^ help: if this is intentional, prefix it with an underscore: `_x`
+   |
+   = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default
+
+warning: 1 warning emitted
+

tests/ui/rfcs/rfc-2005-default-binding-mode/general.rs

@@ -58,6 +58,7 @@ fn match_with_or() {
 fn nested_mixed() {
     match (&Some(5), &Some(6)) {
         (Some(a), &Some(mut b)) => {
+            //~^ WARN value assigned to `b` is never read
             // Here, the `a` will be `&i32`, because in the first half of the tuple
             // we hit a non-reference pattern and shift into `ref` mode.
             //

tests/ui/rfcs/rfc-2005-default-binding-mode/general.stderr

@@ -0,0 +1,11 @@
+warning: value assigned to `b` is never read
+  --> $DIR/general.rs:60:25
+   |
+LL |         (Some(a), &Some(mut b)) => {
+   |                         ^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+   = note: `#[warn(unused_assignments)]` (part of `#[warn(unused)]`) on by default
+
+warning: 1 warning emitted
+

tests/ui/rfcs/rfc-2091-track-caller/std-panic-locations.default.stderr

@@ -0,0 +1,11 @@
+warning: value assigned to `small` is never read
+  --> $DIR/std-panic-locations.rs:47:31
+   |
+LL |     assert_panicked(move || { small[1] += 1; });
+   |                               ^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+   = note: `#[warn(unused_assignments)]` (part of `#[warn(unused)]`) on by default
+
+warning: 1 warning emitted
+

tests/ui/rfcs/rfc-2091-track-caller/std-panic-locations.mir-opt.stderr

@@ -0,0 +1,11 @@
+warning: value assigned to `small` is never read
+  --> $DIR/std-panic-locations.rs:47:31
+   |
+LL |     assert_panicked(move || { small[1] += 1; });
+   |                               ^^^^^^^^^^^^^
+   |
+   = help: maybe it is overwritten before being read?
+   = note: `#[warn(unused_assignments)]` (part of `#[warn(unused)]`) on by default
+
+warning: 1 warning emitted
+