From 4033d19b79244b347a87f3c58d0ad01962935360 Mon Sep 17 00:00:00 2001
From: Scott McMurray <scottmcm@users.noreply.github.com>
Date: Sun, 30 Nov 2025 14:46:36 -0800
Subject: [PATCH] Experimentally add *heterogeneous* `try` blocks

148725 moved the default to being homogeneous; this adds heterogeneous ones back under an obvious-bikeshed syntax so people can experiment with that as well.

Essentially resolves 149025 by letting them move to this syntax instead.
---
 compiler/rustc_ast/src/ast.rs                 | 10 ++-
 compiler/rustc_ast/src/visit.rs               |  4 +-
 compiler/rustc_ast_lowering/src/expr.rs       | 74 +++++++++++++------
 compiler/rustc_ast_lowering/src/lib.rs        | 21 +++++-
 compiler/rustc_ast_passes/src/feature_gate.rs | 10 ++-
 .../rustc_ast_pretty/src/pprust/state/expr.rs |  7 +-
 .../src/assert/context.rs                     |  2 +-
 compiler/rustc_feature/src/unstable.rs        |  2 +
 compiler/rustc_parse/src/parser/expr.rs       | 19 +++--
 compiler/rustc_parse/src/parser/token_type.rs |  2 +
 compiler/rustc_span/src/symbol.rs             |  2 +
 tests/pretty/try-blocks.rs                    |  6 ++
 .../feature-gate-try_blocks_heterogeneous.rs  |  9 +++
 ...ature-gate-try_blocks_heterogeneous.stderr | 17 +++++
 .../try-block-bad-type-heterogeneous.rs       | 21 ++++++
 .../try-block-bad-type-heterogeneous.stderr   | 46 ++++++++++++
 tests/ui/try-block/try-block-heterogeneous.rs | 19 +++++
 tests/ui/unpretty/exhaustive.expanded.stdout  |  8 +-
 tests/ui/unpretty/exhaustive.hir.stderr       | 40 +++++-----
 tests/ui/unpretty/exhaustive.hir.stdout       | 15 +++-
 tests/ui/unpretty/exhaustive.rs               |  3 +
 21 files changed, 278 insertions(+), 59 deletions(-)
 create mode 100644 tests/pretty/try-blocks.rs
 create mode 100644 tests/ui/feature-gates/feature-gate-try_blocks_heterogeneous.rs
 create mode 100644 tests/ui/feature-gates/feature-gate-try_blocks_heterogeneous.stderr
 create mode 100644 tests/ui/try-block/try-block-bad-type-heterogeneous.rs
 create mode 100644 tests/ui/try-block/try-block-bad-type-heterogeneous.stderr
 create mode 100644 tests/ui/try-block/try-block-heterogeneous.rs

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index db7cace49ae8..09dd5c389632 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -1806,8 +1806,14 @@ pub enum ExprKind {
     /// A use expression (`x.use`). Span is of use keyword.
     Use(Box<Expr>, Span),
 
-    /// A try block (`try { ... }`).
-    TryBlock(Box<Block>),
+    /// A try block (`try { ... }`), if the type is `None`, or
+    /// A try block (`try bikeshed Ty { ... }`) if the type is `Some`.
+    ///
+    /// Note that `try bikeshed` is a *deliberately ridiculous* placeholder
+    /// syntax to avoid deciding what keyword or symbol should go there.
+    /// It's that way for experimentation only; an RFC to decide the final
+    /// semantics and syntax would be needed to put it on stabilization-track.
+    TryBlock(Box<Block>, Option<Box<Ty>>),
 
     /// An assignment (`a = foo()`).
     /// The `Span` argument is the span of the `=` token.
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index dde773fd147d..7a0424d39575 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -1048,8 +1048,8 @@ pub fn walk_fn<$($lt,)? V: $Visitor$(<$lt>)?>(vis: &mut V, kind: FnKind<$($lt)?
                     visit_visitable!($($mut)? vis, kind),
                 ExprKind::Try(subexpression) =>
                     visit_visitable!($($mut)? vis, subexpression),
-                ExprKind::TryBlock(body) =>
-                    visit_visitable!($($mut)? vis, body),
+                ExprKind::TryBlock(body, optional_type) =>
+                    visit_visitable!($($mut)? vis, body, optional_type),
                 ExprKind::Lit(token) =>
                     visit_visitable!($($mut)? vis, token),
                 ExprKind::IncludedBytes(bytes) =>
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 524f8b054cb4..7230e1c42474 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -1,3 +1,4 @@
+use std::mem;
 use std::ops::ControlFlow;
 use std::sync::Arc;
 
@@ -27,7 +28,9 @@
     GenericArgsMode, ImplTraitContext, LoweringContext, ParamMode, ResolverAstLoweringExt,
 };
 use crate::errors::{InvalidLegacyConstGenericArg, UseConstGenericArg, YieldInClosure};
-use crate::{AllowReturnTypeNotation, FnDeclKind, ImplTraitPosition, fluent_generated};
+use crate::{
+    AllowReturnTypeNotation, FnDeclKind, ImplTraitPosition, TryBlockScope, fluent_generated,
+};
 
 struct WillCreateDefIdsVisitor {}
 
@@ -199,7 +202,9 @@ pub(super) fn lower_expr_mut(&mut self, e: &Expr) -> hir::Expr<'hir> {
                         )
                     })
                 }
-                ExprKind::TryBlock(body) => self.lower_expr_try_block(body),
+                ExprKind::TryBlock(body, opt_ty) => {
+                    self.lower_expr_try_block(body, opt_ty.as_deref())
+                }
                 ExprKind::Match(expr, arms, kind) => hir::ExprKind::Match(
                     self.lower_expr(expr),
                     self.arena.alloc_from_iter(arms.iter().map(|x| self.lower_arm(x))),
@@ -562,9 +567,14 @@ fn lower_expr_while_in_loop_scope(
     /// Desugar `try { <stmts>; <expr> }` into `{ <stmts>; ::std::ops::Try::from_output(<expr>) }`,
     /// `try { <stmts>; }` into `{ <stmts>; ::std::ops::Try::from_output(()) }`
     /// and save the block id to use it as a break target for desugaring of the `?` operator.
-    fn lower_expr_try_block(&mut self, body: &Block) -> hir::ExprKind<'hir> {
+    fn lower_expr_try_block(&mut self, body: &Block, opt_ty: Option<&Ty>) -> hir::ExprKind<'hir> {
         let body_hir_id = self.lower_node_id(body.id);
-        self.with_catch_scope(body_hir_id, |this| {
+        let new_scope = if opt_ty.is_some() {
+            TryBlockScope::Heterogeneous(body_hir_id)
+        } else {
+            TryBlockScope::Homogeneous(body_hir_id)
+        };
+        let whole_block = self.with_try_block_scope(new_scope, |this| {
             let mut block = this.lower_block_noalloc(body_hir_id, body, true);
 
             // Final expression of the block (if present) or `()` with span at the end of block
@@ -598,8 +608,16 @@ fn lower_expr_try_block(&mut self, body: &Block) -> hir::ExprKind<'hir> {
                 ok_wrapped_span,
             ));
 
-            hir::ExprKind::Block(this.arena.alloc(block), None)
-        })
+            this.arena.alloc(block)
+        });
+
+        if let Some(ty) = opt_ty {
+            let ty = self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Path));
+            let block_expr = self.arena.alloc(self.expr_block(whole_block));
+            hir::ExprKind::Type(block_expr, ty)
+        } else {
+            hir::ExprKind::Block(whole_block, None)
+        }
     }
 
     fn wrap_in_try_constructor(
@@ -1617,10 +1635,14 @@ fn lower_jump_destination(&mut self, id: NodeId, opt_label: Option<Label>) -> hi
         }
     }
 
-    fn with_catch_scope<T>(&mut self, catch_id: hir::HirId, f: impl FnOnce(&mut Self) -> T) -> T {
-        let old_scope = self.catch_scope.replace(catch_id);
+    fn with_try_block_scope<T>(
+        &mut self,
+        scope: TryBlockScope,
+        f: impl FnOnce(&mut Self) -> T,
+    ) -> T {
+        let old_scope = mem::replace(&mut self.try_block_scope, scope);
         let result = f(self);
-        self.catch_scope = old_scope;
+        self.try_block_scope = old_scope;
         result
     }
 
@@ -1978,18 +2000,25 @@ fn lower_expr_try(&mut self, span: Span, sub_expr: &Expr) -> hir::ExprKind<'hir>
             let residual_ident = Ident::with_dummy_span(sym::residual);
             let (residual_local, residual_local_nid) = self.pat_ident(try_span, residual_ident);
             let residual_expr = self.expr_ident_mut(try_span, residual_ident, residual_local_nid);
+
+            let (constructor_item, target_id) = match self.try_block_scope {
+                TryBlockScope::Function => {
+                    (hir::LangItem::TryTraitFromResidual, Err(hir::LoopIdError::OutsideLoopScope))
+                }
+                TryBlockScope::Homogeneous(block_id) => {
+                    (hir::LangItem::ResidualIntoTryType, Ok(block_id))
+                }
+                TryBlockScope::Heterogeneous(block_id) => {
+                    (hir::LangItem::TryTraitFromResidual, Ok(block_id))
+                }
+            };
             let from_residual_expr = self.wrap_in_try_constructor(
-                if self.catch_scope.is_some() {
-                    hir::LangItem::ResidualIntoTryType
-                } else {
-                    hir::LangItem::TryTraitFromResidual
-                },
+                constructor_item,
                 try_span,
                 self.arena.alloc(residual_expr),
                 unstable_span,
             );
-            let ret_expr = if let Some(catch_id) = self.catch_scope {
-                let target_id = Ok(catch_id);
+            let ret_expr = if target_id.is_ok() {
                 self.arena.alloc(self.expr(
                     try_span,
                     hir::ExprKind::Break(
@@ -2044,11 +2073,14 @@ fn lower_expr_yeet(&mut self, span: Span, sub_expr: Option<&Expr>) -> hir::ExprK
             yeeted_span,
         );
 
-        if let Some(catch_id) = self.catch_scope {
-            let target_id = Ok(catch_id);
-            hir::ExprKind::Break(hir::Destination { label: None, target_id }, Some(from_yeet_expr))
-        } else {
-            self.checked_return(Some(from_yeet_expr))
+        match self.try_block_scope {
+            TryBlockScope::Homogeneous(block_id) | TryBlockScope::Heterogeneous(block_id) => {
+                hir::ExprKind::Break(
+                    hir::Destination { label: None, target_id: Ok(block_id) },
+                    Some(from_yeet_expr),
+                )
+            }
+            TryBlockScope::Function => self.checked_return(Some(from_yeet_expr)),
         }
     }
 
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index ab5caff86204..7cd7f787c4ad 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -35,6 +35,7 @@
 #![feature(if_let_guard)]
 // tidy-alphabetical-end
 
+use std::mem;
 use std::sync::Arc;
 
 use rustc_ast::node_id::NodeMap;
@@ -117,7 +118,7 @@ struct LoweringContext<'a, 'hir> {
     /// outside of an `async fn`.
     current_item: Option<Span>,
 
-    catch_scope: Option<HirId>,
+    try_block_scope: TryBlockScope,
     loop_scope: Option<HirId>,
     is_in_loop_condition: bool,
     is_in_dyn_type: bool,
@@ -173,7 +174,7 @@ fn new(tcx: TyCtxt<'hir>, resolver: &'a mut ResolverAstLowering) -> Self {
             trait_map: Default::default(),
 
             // Lowering state.
-            catch_scope: None,
+            try_block_scope: TryBlockScope::Function,
             loop_scope: None,
             is_in_loop_condition: false,
             is_in_dyn_type: false,
@@ -423,6 +424,18 @@ enum AstOwner<'a> {
     ForeignItem(&'a ast::ForeignItem),
 }
 
+#[derive(Copy, Clone, Debug)]
+enum TryBlockScope {
+    /// There isn't a `try` block, so a `?` will use `return`.
+    Function,
+    /// We're inside a `try { … }` block, so a `?` will block-break
+    /// from that block using a type depending only on the argument.
+    Homogeneous(HirId),
+    /// We're inside a `try as _ { … }` block, so a `?` will block-break
+    /// from that block using the type specified.
+    Heterogeneous(HirId),
+}
+
 fn index_crate<'a>(
     node_id_to_def_id: &NodeMap<LocalDefId>,
     krate: &'a Crate,
@@ -943,10 +956,10 @@ fn with_new_scopes<T>(&mut self, scope_span: Span, f: impl FnOnce(&mut Self) ->
 
         let old_contract = self.contract_ensures.take();
 
-        let catch_scope = self.catch_scope.take();
+        let try_block_scope = mem::replace(&mut self.try_block_scope, TryBlockScope::Function);
         let loop_scope = self.loop_scope.take();
         let ret = f(self);
-        self.catch_scope = catch_scope;
+        self.try_block_scope = try_block_scope;
         self.loop_scope = loop_scope;
 
         self.contract_ensures = old_contract;
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 2d87d8c84d7c..9b746508b33e 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -339,9 +339,17 @@ fn visit_generic_args(&mut self, args: &'a ast::GenericArgs) {
 
     fn visit_expr(&mut self, e: &'a ast::Expr) {
         match e.kind {
-            ast::ExprKind::TryBlock(_) => {
+            ast::ExprKind::TryBlock(_, None) => {
                 gate!(&self, try_blocks, e.span, "`try` expression is experimental");
             }
+            ast::ExprKind::TryBlock(_, Some(_)) => {
+                gate!(
+                    &self,
+                    try_blocks_heterogeneous,
+                    e.span,
+                    "`try bikeshed` expression is experimental"
+                );
+            }
             ast::ExprKind::Lit(token::Lit {
                 kind: token::LitKind::Float | token::LitKind::Integer,
                 suffix,
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
index bdf73ac32f0d..7dce7f6d4195 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
@@ -818,10 +818,15 @@ pub(super) fn print_expr_outer_attr_style(
                 );
                 self.word("?")
             }
-            ast::ExprKind::TryBlock(blk) => {
+            ast::ExprKind::TryBlock(blk, opt_ty) => {
                 let cb = self.cbox(0);
                 let ib = self.ibox(0);
                 self.word_nbsp("try");
+                if let Some(ty) = opt_ty {
+                    self.word_nbsp("bikeshed");
+                    self.print_type(ty);
+                    self.space();
+                }
                 self.print_block_with_attrs(blk, attrs, cb, ib)
             }
             ast::ExprKind::UnsafeBinderCast(kind, expr, ty) => {
diff --git a/compiler/rustc_builtin_macros/src/assert/context.rs b/compiler/rustc_builtin_macros/src/assert/context.rs
index 31855cbd4e6c..21b20e2bb974 100644
--- a/compiler/rustc_builtin_macros/src/assert/context.rs
+++ b/compiler/rustc_builtin_macros/src/assert/context.rs
@@ -315,7 +315,7 @@ fn manage_cond_expr(&mut self, expr: &mut Box<Expr>) {
             | ExprKind::Path(_, _)
             | ExprKind::Ret(_)
             | ExprKind::Try(_)
-            | ExprKind::TryBlock(_)
+            | ExprKind::TryBlock(_, _)
             | ExprKind::Type(_, _)
             | ExprKind::Underscore
             | ExprKind::While(_, _, _)
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 3ef4eb00c354..ac01d98b4d1a 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -663,6 +663,8 @@ pub fn internal(&self, feature: Symbol) -> bool {
     (unstable, trivial_bounds, "1.28.0", Some(48214)),
     /// Allows using `try {...}` expressions.
     (unstable, try_blocks, "1.29.0", Some(31436)),
+    /// Allows using `try bikeshed TargetType {...}` expressions.
+    (unstable, try_blocks_heterogeneous, "CURRENT_RUSTC_VERSION", Some(149488)),
     /// Allows `impl Trait` to be used inside type aliases (RFC 2515).
     (unstable, type_alias_impl_trait, "1.38.0", Some(63063)),
     /// Allows creation of instances of a struct by moving fields that have
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 9e7d4bca37d0..fa5e61d24d91 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -3544,15 +3544,20 @@ pub(crate) fn is_builtin(&self) -> bool {
         self.token.is_keyword(kw::Builtin) && self.look_ahead(1, |t| *t == token::Pound)
     }
 
-    /// Parses a `try {...}` expression (`try` token already eaten).
+    /// Parses a `try {...}` or `try bikeshed Ty {...}` expression (`try` token already eaten).
     fn parse_try_block(&mut self, span_lo: Span) -> PResult<'a, Box<Expr>> {
+        let annotation =
+            if self.eat_keyword(exp!(Bikeshed)) { Some(self.parse_ty()?) } else { None };
+
         let (attrs, body) = self.parse_inner_attrs_and_block(None)?;
         if self.eat_keyword(exp!(Catch)) {
             Err(self.dcx().create_err(errors::CatchAfterTry { span: self.prev_token.span }))
         } else {
             let span = span_lo.to(body.span);
-            self.psess.gated_spans.gate(sym::try_blocks, span);
-            Ok(self.mk_expr_with_attrs(span, ExprKind::TryBlock(body), attrs))
+            let gate_sym =
+                if annotation.is_none() { sym::try_blocks } else { sym::try_blocks_heterogeneous };
+            self.psess.gated_spans.gate(gate_sym, span);
+            Ok(self.mk_expr_with_attrs(span, ExprKind::TryBlock(body, annotation), attrs))
         }
     }
 
@@ -3569,7 +3574,11 @@ fn is_do_yeet(&self) -> bool {
 
     fn is_try_block(&self) -> bool {
         self.token.is_keyword(kw::Try)
-            && self.look_ahead(1, |t| *t == token::OpenBrace || t.is_metavar_block())
+            && self.look_ahead(1, |t| {
+                *t == token::OpenBrace
+                    || t.is_metavar_block()
+                    || t.kind == TokenKind::Ident(sym::bikeshed, IdentIsRaw::No)
+            })
             && self.token_uninterpolated_span().at_least_rust_2018()
     }
 
@@ -4264,7 +4273,7 @@ fn visit_expr(&mut self, e: &mut Expr) {
             | ExprKind::Closure(_)
             | ExprKind::Block(_, _)
             | ExprKind::Gen(_, _, _, _)
-            | ExprKind::TryBlock(_)
+            | ExprKind::TryBlock(_, _)
             | ExprKind::Underscore
             | ExprKind::Path(_, _)
             | ExprKind::Break(_, _)
diff --git a/compiler/rustc_parse/src/parser/token_type.rs b/compiler/rustc_parse/src/parser/token_type.rs
index 08c5b06575cd..e5dda7cf9104 100644
--- a/compiler/rustc_parse/src/parser/token_type.rs
+++ b/compiler/rustc_parse/src/parser/token_type.rs
@@ -129,6 +129,7 @@ pub enum TokenType {
     // Keyword-like symbols.
     // tidy-alphabetical-start
     SymAttSyntax,
+    SymBikeshed,
     SymClobberAbi,
     SymInlateout,
     SymInout,
@@ -556,6 +557,7 @@ macro_rules! exp {
     (Yield)          => { exp!(@kw, Yield,      KwYield) };
 
     (AttSyntax)      => { exp!(@sym, att_syntax,      SymAttSyntax) };
+    (Bikeshed)       => { exp!(@sym, bikeshed,        SymBikeshed) };
     (ClobberAbi)     => { exp!(@sym, clobber_abi,     SymClobberAbi) };
     (Inlateout)      => { exp!(@sym, inlateout,       SymInlateout) };
     (Inout)          => { exp!(@sym, inout,           SymInout) };
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 171539b42a6e..c9aaba6cce3b 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -572,6 +572,7 @@
         begin_panic,
         bench,
         bevy_ecs,
+        bikeshed,
         bikeshed_guaranteed_no_drop,
         bin,
         binaryheap_iter,
@@ -2284,6 +2285,7 @@
         truncf64,
         truncf128,
         try_blocks,
+        try_blocks_heterogeneous,
         try_capture,
         try_from,
         try_from_fn,
diff --git a/tests/pretty/try-blocks.rs b/tests/pretty/try-blocks.rs
new file mode 100644
index 000000000000..fc0af2114769
--- /dev/null
+++ b/tests/pretty/try-blocks.rs
@@ -0,0 +1,6 @@
+//@ pp-exact
+//@ edition: 2024
+
+#![feature(try_blocks, try_blocks_heterogeneous)]
+
+fn main() { try { Some(1)? }; try bikeshed Result<u32, ()> { 3 }; }
diff --git a/tests/ui/feature-gates/feature-gate-try_blocks_heterogeneous.rs b/tests/ui/feature-gates/feature-gate-try_blocks_heterogeneous.rs
new file mode 100644
index 000000000000..9f0073eac9ad
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-try_blocks_heterogeneous.rs
@@ -0,0 +1,9 @@
+//@ edition: 2018
+
+pub fn main() {
+    let try_result = try bikeshed Option<_> { //~ ERROR `try bikeshed` expression is experimental
+        let x = 5;
+        x
+    };
+    assert_eq!(try_result, Some(5));
+}
diff --git a/tests/ui/feature-gates/feature-gate-try_blocks_heterogeneous.stderr b/tests/ui/feature-gates/feature-gate-try_blocks_heterogeneous.stderr
new file mode 100644
index 000000000000..0d31dc507fdd
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-try_blocks_heterogeneous.stderr
@@ -0,0 +1,17 @@
+error[E0658]: `try bikeshed` expression is experimental
+  --> $DIR/feature-gate-try_blocks_heterogeneous.rs:4:22
+   |
+LL |       let try_result = try bikeshed Option<_> {
+   |  ______________________^
+LL | |         let x = 5;
+LL | |         x
+LL | |     };
+   | |_____^
+   |
+   = note: see issue #149488 <https://github.com/rust-lang/rust/issues/149488> for more information
+   = help: add `#![feature(try_blocks_heterogeneous)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/try-block/try-block-bad-type-heterogeneous.rs b/tests/ui/try-block/try-block-bad-type-heterogeneous.rs
new file mode 100644
index 000000000000..b099651bf8a9
--- /dev/null
+++ b/tests/ui/try-block/try-block-bad-type-heterogeneous.rs
@@ -0,0 +1,21 @@
+//@ edition: 2018
+
+#![feature(try_blocks_heterogeneous)]
+
+pub fn main() {
+    let res = try bikeshed Result<u32, std::array::TryFromSliceError> {
+        Err("")?; //~ ERROR `?` couldn't convert the error
+        5
+    };
+
+    let res = try bikeshed Result<i32, i32> {
+        "" //~ ERROR type mismatch
+    };
+
+    let res = try bikeshed Result<i32, i32> { }; //~ ERROR type mismatch
+
+    let res = try bikeshed () { };
+    //~^ ERROR a `try` block must return `Result` or `Option`
+
+    let res = try bikeshed i32 { 5 }; //~ ERROR a `try` block must return `Result` or `Option`
+}
diff --git a/tests/ui/try-block/try-block-bad-type-heterogeneous.stderr b/tests/ui/try-block/try-block-bad-type-heterogeneous.stderr
new file mode 100644
index 000000000000..7c7cedd392e6
--- /dev/null
+++ b/tests/ui/try-block/try-block-bad-type-heterogeneous.stderr
@@ -0,0 +1,46 @@
+error[E0277]: `?` couldn't convert the error to `TryFromSliceError`
+  --> $DIR/try-block-bad-type-heterogeneous.rs:7:16
+   |
+LL |         Err("")?;
+   |         -------^ the trait `From<&str>` is not implemented for `TryFromSliceError`
+   |         |
+   |         this can't be annotated with `?` because it has type `Result<_, &str>`
+   |
+   = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
+help: the trait `From<&str>` is not implemented for `TryFromSliceError`
+      but trait `From<Infallible>` is implemented for it
+  --> $SRC_DIR/core/src/array/mod.rs:LL:COL
+   = help: for that trait implementation, expected `Infallible`, found `&str`
+
+error[E0271]: type mismatch resolving `<Result<i32, i32> as Try>::Output == &str`
+  --> $DIR/try-block-bad-type-heterogeneous.rs:12:9
+   |
+LL |         ""
+   |         ^^ expected `&str`, found `i32`
+
+error[E0271]: type mismatch resolving `<Result<i32, i32> as Try>::Output == ()`
+  --> $DIR/try-block-bad-type-heterogeneous.rs:15:47
+   |
+LL |     let res = try bikeshed Result<i32, i32> { };
+   |                                               ^ expected `()`, found `i32`
+
+error[E0277]: a `try` block must return `Result` or `Option` (or another type that implements `Try`)
+  --> $DIR/try-block-bad-type-heterogeneous.rs:17:33
+   |
+LL |     let res = try bikeshed () { };
+   |                                 ^ could not wrap the final value of the block as `()` doesn't implement `Try`
+   |
+   = help: the trait `Try` is not implemented for `()`
+
+error[E0277]: a `try` block must return `Result` or `Option` (or another type that implements `Try`)
+  --> $DIR/try-block-bad-type-heterogeneous.rs:20:34
+   |
+LL |     let res = try bikeshed i32 { 5 };
+   |                                  ^ could not wrap the final value of the block as `i32` doesn't implement `Try`
+   |
+   = help: the trait `Try` is not implemented for `i32`
+
+error: aborting due to 5 previous errors
+
+Some errors have detailed explanations: E0271, E0277.
+For more information about an error, try `rustc --explain E0271`.
diff --git a/tests/ui/try-block/try-block-heterogeneous.rs b/tests/ui/try-block/try-block-heterogeneous.rs
new file mode 100644
index 000000000000..0b17b7c8655d
--- /dev/null
+++ b/tests/ui/try-block/try-block-heterogeneous.rs
@@ -0,0 +1,19 @@
+//@ check-pass
+//@ edition: 2018
+
+#![feature(try_blocks_heterogeneous)]
+
+fn foo() -> Result<(), u16> { Ok(()) }
+
+fn bar() -> Result<(), u32> { Ok(()) }
+
+fn whatever() -> Result<(), String> {
+    try bikeshed _ {}
+}
+
+fn main() {
+    try bikeshed Result<(), u64> {
+        foo()?;
+        bar()?;
+    };
+}
diff --git a/tests/ui/unpretty/exhaustive.expanded.stdout b/tests/ui/unpretty/exhaustive.expanded.stdout
index 9e6797c727f0..1fc9e6a72693 100644
--- a/tests/ui/unpretty/exhaustive.expanded.stdout
+++ b/tests/ui/unpretty/exhaustive.expanded.stdout
@@ -28,6 +28,7 @@
 #![feature(trace_macros)]
 #![feature(trait_alias)]
 #![feature(try_blocks)]
+#![feature(try_blocks_heterogeneous)]
 #![feature(yeet_expr)]
 #![allow(incomplete_features)]
 #[macro_use]
@@ -222,7 +223,12 @@ mod expressions {
     }
 
     /// ExprKind::TryBlock
-    fn expr_try_block() { try {} try { return; } }
+    fn expr_try_block() {
+        try {}
+        try { return; }
+        try bikeshed Option<_> {}
+        try bikeshed Option<String> { None? }
+    }
 
     /// ExprKind::Assign
     fn expr_assign() { let expr; expr = true; }
diff --git a/tests/ui/unpretty/exhaustive.hir.stderr b/tests/ui/unpretty/exhaustive.hir.stderr
index eb5c186bd2c0..f6800fc9c1e6 100644
--- a/tests/ui/unpretty/exhaustive.hir.stderr
+++ b/tests/ui/unpretty/exhaustive.hir.stderr
@@ -1,17 +1,17 @@
 error[E0697]: closures cannot be static
-  --> $DIR/exhaustive.rs:210:9
+  --> $DIR/exhaustive.rs:211:9
    |
 LL |         static || value;
    |         ^^^^^^^^^
 
 error[E0697]: closures cannot be static
-  --> $DIR/exhaustive.rs:211:9
+  --> $DIR/exhaustive.rs:212:9
    |
 LL |         static move || value;
    |         ^^^^^^^^^^^^^^
 
 error[E0728]: `await` is only allowed inside `async` functions and blocks
-  --> $DIR/exhaustive.rs:240:13
+  --> $DIR/exhaustive.rs:241:13
    |
 LL |     fn expr_await() {
    |     --------------- this is not `async`
@@ -20,19 +20,19 @@ LL |         fut.await;
    |             ^^^^^ only allowed inside `async` functions and blocks
 
 error: in expressions, `_` can only be used on the left-hand side of an assignment
-  --> $DIR/exhaustive.rs:289:9
+  --> $DIR/exhaustive.rs:292:9
    |
 LL |         _;
    |         ^ `_` not allowed here
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:299:9
+  --> $DIR/exhaustive.rs:302:9
    |
 LL |         x::();
    |         ^^^^^ only `Fn` traits may use parentheses
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:300:9
+  --> $DIR/exhaustive.rs:303:9
    |
 LL |         x::(T, T) -> T;
    |         ^^^^^^^^^^^^^^ only `Fn` traits may use parentheses
@@ -44,31 +44,31 @@ LL +         x::<T, T> -> T;
    |
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:301:9
+  --> $DIR/exhaustive.rs:304:9
    |
 LL |         crate::() -> ()::expressions::() -> ()::expr_path;
    |         ^^^^^^^^^^^^^^^ only `Fn` traits may use parentheses
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:301:26
+  --> $DIR/exhaustive.rs:304:26
    |
 LL |         crate::() -> ()::expressions::() -> ()::expr_path;
    |                          ^^^^^^^^^^^^^^^^^^^^^ only `Fn` traits may use parentheses
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:304:9
+  --> $DIR/exhaustive.rs:307:9
    |
 LL |         core::()::marker::()::PhantomData;
    |         ^^^^^^^^ only `Fn` traits may use parentheses
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:304:19
+  --> $DIR/exhaustive.rs:307:19
    |
 LL |         core::()::marker::()::PhantomData;
    |                   ^^^^^^^^^^ only `Fn` traits may use parentheses
 
 error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
-  --> $DIR/exhaustive.rs:391:9
+  --> $DIR/exhaustive.rs:394:9
    |
 LL |         yield;
    |         ^^^^^
@@ -79,7 +79,7 @@ LL |     #[coroutine] fn expr_yield() {
    |     ++++++++++++
 
 error[E0703]: invalid ABI: found `C++`
-  --> $DIR/exhaustive.rs:471:23
+  --> $DIR/exhaustive.rs:474:23
    |
 LL |         unsafe extern "C++" {}
    |                       ^^^^^ invalid ABI
@@ -87,7 +87,7 @@ LL |         unsafe extern "C++" {}
    = note: invoke `rustc --print=calling-conventions` for a full list of supported calling conventions
 
 error: `..` patterns are not allowed here
-  --> $DIR/exhaustive.rs:678:13
+  --> $DIR/exhaustive.rs:681:13
    |
 LL |         let ..;
    |             ^^
@@ -95,13 +95,13 @@ LL |         let ..;
    = note: only allowed in tuple, tuple struct, and slice patterns
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:793:16
+  --> $DIR/exhaustive.rs:796:16
    |
 LL |         let _: T() -> !;
    |                ^^^^^^^^ only `Fn` traits may use parentheses
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:807:16
+  --> $DIR/exhaustive.rs:810:16
    |
 LL |         let _: impl Send;
    |                ^^^^^^^^^
@@ -112,7 +112,7 @@ LL |         let _: impl Send;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:808:16
+  --> $DIR/exhaustive.rs:811:16
    |
 LL |         let _: impl Send + 'static;
    |                ^^^^^^^^^^^^^^^^^^^
@@ -123,7 +123,7 @@ LL |         let _: impl Send + 'static;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:809:16
+  --> $DIR/exhaustive.rs:812:16
    |
 LL |         let _: impl 'static + Send;
    |                ^^^^^^^^^^^^^^^^^^^
@@ -134,7 +134,7 @@ LL |         let _: impl 'static + Send;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:810:16
+  --> $DIR/exhaustive.rs:813:16
    |
 LL |         let _: impl ?Sized;
    |                ^^^^^^^^^^^
@@ -145,7 +145,7 @@ LL |         let _: impl ?Sized;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:811:16
+  --> $DIR/exhaustive.rs:814:16
    |
 LL |         let _: impl [const] Clone;
    |                ^^^^^^^^^^^^^^^^^^
@@ -156,7 +156,7 @@ LL |         let _: impl [const] Clone;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:812:16
+  --> $DIR/exhaustive.rs:815:16
    |
 LL |         let _: impl for<'a> Send;
    |                ^^^^^^^^^^^^^^^^^
diff --git a/tests/ui/unpretty/exhaustive.hir.stdout b/tests/ui/unpretty/exhaustive.hir.stdout
index 873febbbd84d..9396e937d843 100644
--- a/tests/ui/unpretty/exhaustive.hir.stdout
+++ b/tests/ui/unpretty/exhaustive.hir.stdout
@@ -27,6 +27,7 @@
 #![feature(trace_macros)]
 #![feature(trait_alias)]
 #![feature(try_blocks)]
+#![feature(try_blocks_heterogeneous)]
 #![feature(yeet_expr)]
 #![allow(incomplete_features)]
 #[attr = MacroUse {arguments: UseAll}]
@@ -253,7 +254,19 @@ mod expressions {
     }
 
     /// ExprKind::TryBlock
-    fn expr_try_block() { { from_output(()) } { return; from_output(()) } }
+    fn expr_try_block() {
+        { from_output(()) }
+        { return; from_output(()) }
+        type_ascribe!({ from_output(()) }, Option<_>);
+        type_ascribe!({
+                from_output(match branch(None) {
+                        Break {  0: residual } => #[allow(unreachable_code)]
+                            break from_residual(residual),
+                        Continue {  0: val } => #[allow(unreachable_code)]
+                            val,
+                    })
+            }, Option<String>)
+    }
 
     /// ExprKind::Assign
     fn expr_assign() { let expr; expr = true; }
diff --git a/tests/ui/unpretty/exhaustive.rs b/tests/ui/unpretty/exhaustive.rs
index 0983a0a7e437..0bbc87845695 100644
--- a/tests/ui/unpretty/exhaustive.rs
+++ b/tests/ui/unpretty/exhaustive.rs
@@ -27,6 +27,7 @@
 #![feature(trace_macros)]
 #![feature(trait_alias)]
 #![feature(try_blocks)]
+#![feature(try_blocks_heterogeneous)]
 #![feature(yeet_expr)]
 #![allow(incomplete_features)]
 
@@ -244,6 +245,8 @@ fn expr_await() {
     fn expr_try_block() {
         try {}
         try { return; }
+        try bikeshed Option<_> { }
+        try bikeshed Option<String> { None? }
     }
 
     /// ExprKind::Assign