Rollup merge of #155549 - nnethercote:rm-lifetimes, r=JohnTitor

Remove some unnecessary lifetimes.

We have a number of structs with more lifetimes than necessary. This commit removes them.

LLM disclosure: I asked Claude Code to check for unnecessary lifetimes in all types with three or more lifetimes, and it produced a list of candidates (half of which were invalid). I did the modifications for the valid cases myself, and found a couple more cases along the way.

r? @JohnTitor

compiler/rustc_borrowck/src/polonius/dump.rs

@@ -107,7 +107,7 @@ fn on_successor_discovered(&mut self, current_node: LocalizedNode, successor: Lo
 /// - a mermaid graph of the NLL regions and the constraints between them
 /// - a mermaid graph of the NLL SCCs and the constraints between them
 fn emit_polonius_dump<'tcx>(
-    dumper: &MirDumper<'_, '_, 'tcx>,
+    dumper: &MirDumper<'_, 'tcx>,
     body: &Body<'tcx>,
     regioncx: &RegionInferenceContext<'tcx>,
     borrow_set: &BorrowSet<'tcx>,
@@ -186,7 +186,7 @@ fn emit_polonius_dump<'tcx>(
 
 /// Emits the polonius MIR, as escaped HTML.
 fn emit_html_mir<'tcx>(
-    dumper: &MirDumper<'_, '_, 'tcx>,
+    dumper: &MirDumper<'_, 'tcx>,
     body: &Body<'tcx>,
     out: &mut dyn io::Write,
 ) -> io::Result<()> {

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1901,14 +1901,14 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     }
 }
 
-struct FnCallDiagCtxt<'a, 'b, 'tcx> {
+struct FnCallDiagCtxt<'a, 'tcx> {
-    arg_matching_ctxt: ArgMatchingCtxt<'a, 'b, 'tcx>,
+    arg_matching_ctxt: ArgMatchingCtxt<'a, 'tcx>,
     errors: Vec<Error<'tcx>>,
     matched_inputs: IndexVec<ExpectedIdx, Option<ProvidedIdx>>,
 }
 
-impl<'a, 'b, 'tcx> Deref for FnCallDiagCtxt<'a, 'b, 'tcx> {
+impl<'a, 'tcx> Deref for FnCallDiagCtxt<'a, 'tcx> {
-    type Target = ArgMatchingCtxt<'a, 'b, 'tcx>;
+    type Target = ArgMatchingCtxt<'a, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
         &self.arg_matching_ctxt
@@ -1921,9 +1921,9 @@ enum ArgumentsFormatting {
     Multiline { fallback_indent: String, brace_indent: String },
 }
 
-impl<'a, 'b, 'tcx> FnCallDiagCtxt<'a, 'b, 'tcx> {
+impl<'a, 'tcx> FnCallDiagCtxt<'a, 'tcx> {
     fn new(
-        arg: &'a FnCtxt<'b, 'tcx>,
+        arg: &'a FnCtxt<'a, 'tcx>,
         compatibility_diagonal: IndexVec<ProvidedIdx, Compatibility<'tcx>>,
         formal_and_expected_inputs: IndexVec<ExpectedIdx, (Ty<'tcx>, Ty<'tcx>)>,
         provided_args: IndexVec<ProvidedIdx, &'tcx Expr<'tcx>>,
@@ -2618,7 +2618,7 @@ fn has_error_or_infer<'tcx>(tys: impl IntoIterator<Item = Ty<'tcx>>) -> bool {
         (suggestions, labels, suggestion_text)
     }
 
-    fn label_generic_mismatches(&self, err: &mut Diag<'b>) {
+    fn label_generic_mismatches(&self, err: &mut Diag<'a>) {
         self.fn_ctxt.label_generic_mismatches(
             err,
             self.fn_def_id,
@@ -2778,22 +2778,22 @@ fn suggestion_code(&self) -> (Span, String) {
     }
 }
 
-struct ArgMatchingCtxt<'a, 'b, 'tcx> {
+struct ArgMatchingCtxt<'a, 'tcx> {
-    args_ctxt: ArgsCtxt<'a, 'b, 'tcx>,
+    args_ctxt: ArgsCtxt<'a, 'tcx>,
     provided_arg_tys: IndexVec<ProvidedIdx, (Ty<'tcx>, Span)>,
 }
 
-impl<'a, 'b, 'tcx> Deref for ArgMatchingCtxt<'a, 'b, 'tcx> {
+impl<'a, 'tcx> Deref for ArgMatchingCtxt<'a, 'tcx> {
-    type Target = ArgsCtxt<'a, 'b, 'tcx>;
+    type Target = ArgsCtxt<'a, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
         &self.args_ctxt
     }
 }
 
-impl<'a, 'b, 'tcx> ArgMatchingCtxt<'a, 'b, 'tcx> {
+impl<'a, 'tcx> ArgMatchingCtxt<'a, 'tcx> {
     fn new(
-        arg: &'a FnCtxt<'b, 'tcx>,
+        arg: &'a FnCtxt<'a, 'tcx>,
         compatibility_diagonal: IndexVec<ProvidedIdx, Compatibility<'tcx>>,
         formal_and_expected_inputs: IndexVec<ExpectedIdx, (Ty<'tcx>, Ty<'tcx>)>,
         provided_args: IndexVec<ProvidedIdx, &'tcx Expr<'tcx>>,
@@ -2924,23 +2924,23 @@ fn remove_idx_is_perfect(&self, idx: usize) -> bool {
     }
 }
 
-struct ArgsCtxt<'a, 'b, 'tcx> {
+struct ArgsCtxt<'a, 'tcx> {
-    call_ctxt: CallCtxt<'a, 'b, 'tcx>,
+    call_ctxt: CallCtxt<'a, 'tcx>,
     call_metadata: CallMetadata,
     args_span: Span,
 }
 
-impl<'a, 'b, 'tcx> Deref for ArgsCtxt<'a, 'b, 'tcx> {
+impl<'a, 'tcx> Deref for ArgsCtxt<'a, 'tcx> {
-    type Target = CallCtxt<'a, 'b, 'tcx>;
+    type Target = CallCtxt<'a, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
         &self.call_ctxt
     }
 }
 
-impl<'a, 'b, 'tcx> ArgsCtxt<'a, 'b, 'tcx> {
+impl<'a, 'tcx> ArgsCtxt<'a, 'tcx> {
     fn new(
-        arg: &'a FnCtxt<'b, 'tcx>,
+        arg: &'a FnCtxt<'a, 'tcx>,
         compatibility_diagonal: IndexVec<ProvidedIdx, Compatibility<'tcx>>,
         formal_and_expected_inputs: IndexVec<ExpectedIdx, (Ty<'tcx>, Ty<'tcx>)>,
         provided_args: IndexVec<ProvidedIdx, &'tcx Expr<'tcx>>,
@@ -2951,7 +2951,7 @@ fn new(
         call_expr: &'tcx Expr<'tcx>,
         tuple_arguments: TupleArgumentsFlag,
     ) -> Self {
-        let call_ctxt: CallCtxt<'_, '_, '_> = CallCtxt::new(
+        let call_ctxt: CallCtxt<'_, '_> = CallCtxt::new(
             arg,
             compatibility_diagonal,
             formal_and_expected_inputs,
@@ -3058,8 +3058,8 @@ struct CallMetadata {
     is_method: bool,
 }
 
-struct CallCtxt<'a, 'b, 'tcx> {
+struct CallCtxt<'a, 'tcx> {
-    fn_ctxt: &'a FnCtxt<'b, 'tcx>,
+    fn_ctxt: &'a FnCtxt<'a, 'tcx>,
     compatibility_diagonal: IndexVec<ProvidedIdx, Compatibility<'tcx>>,
     formal_and_expected_inputs: IndexVec<ExpectedIdx, (Ty<'tcx>, Ty<'tcx>)>,
     provided_args: IndexVec<ProvidedIdx, &'tcx hir::Expr<'tcx>>,
@@ -3073,17 +3073,17 @@ struct CallCtxt<'a, 'b, 'tcx> {
     callee_ty: Option<Ty<'tcx>>,
 }
 
-impl<'a, 'b, 'tcx> Deref for CallCtxt<'a, 'b, 'tcx> {
+impl<'a, 'tcx> Deref for CallCtxt<'a, 'tcx> {
-    type Target = &'a FnCtxt<'b, 'tcx>;
+    type Target = &'a FnCtxt<'a, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
         &self.fn_ctxt
     }
 }
 
-impl<'a, 'b, 'tcx> CallCtxt<'a, 'b, 'tcx> {
+impl<'a, 'tcx> CallCtxt<'a, 'tcx> {
     fn new(
-        fn_ctxt: &'a FnCtxt<'b, 'tcx>,
+        fn_ctxt: &'a FnCtxt<'a, 'tcx>,
         compatibility_diagonal: IndexVec<ProvidedIdx, Compatibility<'tcx>>,
         formal_and_expected_inputs: IndexVec<ExpectedIdx, (Ty<'tcx>, Ty<'tcx>)>,
         provided_args: IndexVec<ProvidedIdx, &'tcx hir::Expr<'tcx>>,
@@ -3093,7 +3093,7 @@ fn new(
         call_span: Span,
         call_expr: &'tcx hir::Expr<'tcx>,
         tuple_arguments: TupleArgumentsFlag,
-    ) -> CallCtxt<'a, 'b, 'tcx> {
+    ) -> CallCtxt<'a, 'tcx> {
         let callee_expr = match &call_expr.peel_blocks().kind {
             hir::ExprKind::Call(callee, _) => Some(*callee),
             hir::ExprKind::MethodCall(_, receiver, ..) => {

compiler/rustc_hir_typeck/src/method/prelude_edition_lints.rs

@@ -16,15 +16,15 @@
 use crate::FnCtxt;
 use crate::method::probe::{self, Pick};
 
-struct AmbiguousTraitMethodCall<'a, 'b, 'tcx> {
+struct AmbiguousTraitMethodCall<'a, 'tcx> {
     segment_name: Symbol,
     self_expr_span: Span,
     pick: &'a Pick<'tcx>,
     tcx: TyCtxt<'tcx>,
-    edition: &'b str,
+    edition: &'static str,
 }
 
-impl<'a, 'b, 'c, 'tcx> Diagnostic<'a, ()> for AmbiguousTraitMethodCall<'b, 'c, 'tcx> {
+impl<'a, 'b, 'tcx> Diagnostic<'a, ()> for AmbiguousTraitMethodCall<'b, 'tcx> {
     fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, ()> {
         let Self { segment_name, self_expr_span, pick, tcx, edition } = self;
         let mut lint = Diag::new(
@@ -80,20 +80,18 @@ fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, ()> {
     }
 }
 
-struct AmbiguousTraitMethod<'a, 'b, 'tcx, 'pcx, 'fnctx> {
+struct AmbiguousTraitMethod<'a, 'tcx, 'fnctx> {
-    segment: &'a hir::PathSegment<'pcx>,
+    segment: &'a hir::PathSegment<'tcx>,
     call_expr: &'tcx hir::Expr<'tcx>,
     self_expr: &'tcx hir::Expr<'tcx>,
     pick: &'a Pick<'tcx>,
     args: &'tcx [hir::Expr<'tcx>],
-    edition: &'b str,
+    edition: &'static str,
     span: Span,
     this: &'a FnCtxt<'fnctx, 'tcx>,
 }
 
-impl<'a, 'b, 'c, 'tcx, 'pcx, 'fnctx> Diagnostic<'a, ()>
+impl<'a, 'c, 'tcx, 'fnctx> Diagnostic<'a, ()> for AmbiguousTraitMethod<'c, 'tcx, 'fnctx> {
-    for AmbiguousTraitMethod<'b, 'c, 'tcx, 'pcx, 'fnctx>
-{
     fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, ()> {
         let Self { segment, call_expr, self_expr, pick, args, edition, span, this } = self;
         let mut lint = Diag::new(
@@ -158,7 +156,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub(super) fn lint_edition_dependent_dot_call(
         &self,
         self_ty: Ty<'tcx>,
-        segment: &hir::PathSegment<'_>,
+        segment: &hir::PathSegment<'tcx>,
         span: Span,
         call_expr: &'tcx hir::Expr<'tcx>,
         self_expr: &'tcx hir::Expr<'tcx>,

compiler/rustc_hir_typeck/src/upvar.rs

@@ -958,15 +958,15 @@ fn perform_2229_migration_analysis(
         capture_clause: hir::CaptureBy,
         span: Span,
     ) {
-        struct MigrationLint<'a, 'b, 'tcx> {
+        struct MigrationLint<'a, 'tcx> {
             closure_def_id: LocalDefId,
-            this: &'a FnCtxt<'b, 'tcx>,
+            this: &'a FnCtxt<'a, 'tcx>,
             body_id: hir::BodyId,
             need_migrations: Vec<NeededMigration>,
             migration_message: String,
         }
 
-        impl<'a, 'b, 'c, 'tcx> Diagnostic<'a, ()> for MigrationLint<'b, 'c, 'tcx> {
+        impl<'a, 'b, 'tcx> Diagnostic<'a, ()> for MigrationLint<'b, 'tcx> {
             fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, ()> {
                 let Self { closure_def_id, this, body_id, need_migrations, migration_message } =
                     self;
@@ -2084,8 +2084,8 @@ fn drop_location_span(tcx: TyCtxt<'_>, hir_id: HirId) -> Span {
     tcx.sess.source_map().end_point(owner_span)
 }
 
-struct InferBorrowKind<'fcx, 'a, 'tcx> {
+struct InferBorrowKind<'a, 'tcx> {
-    fcx: &'fcx FnCtxt<'a, 'tcx>,
+    fcx: &'a FnCtxt<'a, 'tcx>,
     // The def-id of the closure whose kind and upvar accesses are being inferred.
     closure_def_id: LocalDefId,
 
@@ -2119,7 +2119,7 @@ struct InferBorrowKind<'fcx, 'a, 'tcx> {
     fake_reads: Vec<(Place<'tcx>, FakeReadCause, HirId)>,
 }
 
-impl<'fcx, 'a, 'tcx> euv::Delegate<'tcx> for InferBorrowKind<'fcx, 'a, 'tcx> {
+impl<'a, 'tcx> euv::Delegate<'tcx> for InferBorrowKind<'a, 'tcx> {
     #[instrument(skip(self), level = "debug")]
     fn fake_read(
         &mut self,

compiler/rustc_lint/src/default_could_be_derived.rs

@@ -156,15 +156,15 @@ fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_
     }
 }
 
-struct WrongDefaultImpl<'a, 'hir, 'tcx> {
+struct WrongDefaultImpl<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     type_def_id: DefId,
-    orig_fields: FxHashMap<Symbol, &'a hir::FieldDef<'hir>>,
+    orig_fields: FxHashMap<Symbol, &'a hir::FieldDef<'tcx>>,
-    fields: &'a [hir::ExprField<'hir>],
+    fields: &'a [hir::ExprField<'tcx>],
     impl_span: Span,
 }
 
-impl<'a, 'b, 'hir, 'tcx> Diagnostic<'a, ()> for WrongDefaultImpl<'b, 'hir, 'tcx> {
+impl<'a, 'b, 'tcx> Diagnostic<'a, ()> for WrongDefaultImpl<'b, 'tcx> {
     fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, ()> {
         let Self { tcx, type_def_id, orig_fields, fields, impl_span } = self;
         let mut diag =

compiler/rustc_middle/src/mir/pretty.rs

@@ -61,14 +61,14 @@ pub fn from_cli(tcx: TyCtxt<'_>) -> Self {
 /// Manages MIR dumping, which is MIR writing done to a file with a specific name. In particular,
 /// it makes it impossible to dump MIR to one of these files when it hasn't been requested from the
 /// command line. Layered on top of `MirWriter`, which does the actual writing.
-pub struct MirDumper<'dis, 'de, 'tcx> {
+pub struct MirDumper<'a, 'tcx> {
     show_pass_num: bool,
     pass_name: &'static str,
-    disambiguator: &'dis dyn Display,
+    disambiguator: &'a dyn Display,
-    writer: MirWriter<'de, 'tcx>,
+    writer: MirWriter<'a, 'tcx>,
 }
 
-impl<'dis, 'de, 'tcx> MirDumper<'dis, 'de, 'tcx> {
+impl<'a, 'tcx> MirDumper<'a, 'tcx> {
     // If dumping should be performed (e.g. because it was requested on the
     // CLI), returns a `MirDumper` with default values for the following fields:
     // - `show_pass_num`: `false`
@@ -112,7 +112,7 @@ pub fn set_show_pass_num(mut self) -> Self {
     }
 
     #[must_use]
-    pub fn set_disambiguator(mut self, disambiguator: &'dis dyn Display) -> Self {
+    pub fn set_disambiguator(mut self, disambiguator: &'a dyn Display) -> Self {
         self.disambiguator = disambiguator;
         self
     }
@@ -120,7 +120,7 @@ pub fn set_disambiguator(mut self, disambiguator: &'dis dyn Display) -> Self {
     #[must_use]
     pub fn set_extra_data(
         mut self,
-        extra_data: &'de dyn Fn(PassWhere, &mut dyn io::Write) -> io::Result<()>,
+        extra_data: &'a dyn Fn(PassWhere, &mut dyn io::Write) -> io::Result<()>,
     ) -> Self {
         self.writer.extra_data = extra_data;
         self
@@ -369,13 +369,13 @@ pub fn write_mir_pretty<'tcx>(
 }
 
 /// Does the writing of MIR to output, e.g. a file.
-pub struct MirWriter<'de, 'tcx> {
+pub struct MirWriter<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    extra_data: &'de dyn Fn(PassWhere, &mut dyn io::Write) -> io::Result<()>,
+    extra_data: &'a dyn Fn(PassWhere, &mut dyn io::Write) -> io::Result<()>,
     options: PrettyPrintMirOptions,
 }
 
-impl<'de, 'tcx> MirWriter<'de, 'tcx> {
+impl<'a, 'tcx> MirWriter<'a, 'tcx> {
     pub fn new(tcx: TyCtxt<'tcx>) -> Self {
         MirWriter { tcx, extra_data: &|_, _| Ok(()), options: PrettyPrintMirOptions::from_cli(tcx) }
     }
@@ -709,7 +709,7 @@ pub fn dump_mir_def_ids(tcx: TyCtxt<'_>, single: Option<DefId>) -> Vec<DefId> {
 ///////////////////////////////////////////////////////////////////////////
 // Basic blocks and their parts (statements, terminators, ...)
 
-impl<'de, 'tcx> MirWriter<'de, 'tcx> {
+impl<'a, 'tcx> MirWriter<'a, 'tcx> {
     /// Write out a human-readable textual representation for the given basic block.
     fn write_basic_block(
         &self,

compiler/rustc_mir_build/src/errors.rs

@@ -649,14 +649,14 @@ pub(crate) enum UnusedUnsafeEnclosing {
     },
 }
 
-pub(crate) struct NonExhaustivePatternsTypeNotEmpty<'p, 'tcx, 'm> {
+pub(crate) struct NonExhaustivePatternsTypeNotEmpty<'a, 'tcx> {
-    pub(crate) cx: &'m RustcPatCtxt<'p, 'tcx>,
+    pub(crate) cx: &'a RustcPatCtxt<'a, 'tcx>,
     pub(crate) scrut_span: Span,
     pub(crate) braces_span: Option<Span>,
     pub(crate) ty: Ty<'tcx>,
 }
 
-impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for NonExhaustivePatternsTypeNotEmpty<'_, '_, '_> {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for NonExhaustivePatternsTypeNotEmpty<'_, '_> {
     fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let mut diag =
             Diag::new(dcx, level, msg!("non-exhaustive patterns: type `{$ty}` is non-empty"));

compiler/rustc_monomorphize/src/graph_checks/statics.rs

@@ -37,14 +37,14 @@ struct StaticSccIdx {}
 // Adjacency-list graph for statics using `StaticNodeIdx` as node type.
 // We cannot use `DefId` as the node type directly because each node must be
 // represented by an index in the range `0..num_nodes`.
-struct StaticRefGraph<'a, 'b, 'tcx> {
+struct StaticRefGraph<'a, 'tcx> {
     // maps from `StaticNodeIdx` to `DefId` and vice versa
     statics: &'a FxIndexSet<DefId>,
     // contains for each `MonoItem` the `MonoItem`s it uses
-    used_map: &'b UnordMap<MonoItem<'tcx>, Vec<MonoItem<'tcx>>>,
+    used_map: &'a UnordMap<MonoItem<'tcx>, Vec<MonoItem<'tcx>>>,
 }
 
-impl<'a, 'b, 'tcx> DirectedGraph for StaticRefGraph<'a, 'b, 'tcx> {
+impl<'a, 'tcx> DirectedGraph for StaticRefGraph<'a, 'tcx> {
     type Node = StaticNodeIdx;
 
     fn num_nodes(&self) -> usize {
@@ -52,7 +52,7 @@ fn num_nodes(&self) -> usize {
     }
 }
 
-impl<'a, 'b, 'tcx> Successors for StaticRefGraph<'a, 'b, 'tcx> {
+impl<'a, 'tcx> Successors for StaticRefGraph<'a, 'tcx> {
     fn successors(&self, node_idx: StaticNodeIdx) -> impl Iterator<Item = StaticNodeIdx> {
         let def_id = self.statics[node_idx.index()];
         self.used_map[&MonoItem::Static(def_id)].iter().filter_map(|&mono_item| match mono_item {