Point at tail expression on rpit E0277

``` error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:7:5: 7:8}: Coroutine` is not satisfied --> $DIR/gen_block_is_coro.rs:6:13 | LL | fn foo() -> impl Coroutine<Yield = u32, Return = ()> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:7:5: 7:8}` LL | gen { yield 42 } | ---------------- return type was inferred to be `{gen block@$DIR/gen_block_is_coro.rs:7:5: 7:8}` here ``` The secondary span label is new.
rust-lang · Oct 25, 2024 · 6651238 · 6651238
1 parent a50c8eb
commit 6651238
Show file tree

Hide file tree

Showing 20 changed files with 121 additions and 32 deletions.
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -3567,17 +3567,34 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 )]);
             }
             ObligationCauseCode::OpaqueReturnType(expr_info) => {
-                if let Some((expr_ty, hir_id)) = expr_info {
-                    let expr_ty = self.tcx.short_ty_string(expr_ty, long_ty_file);
-                    let expr = self.infcx.tcx.hir().expect_expr(hir_id);
-                    err.span_label(
-                        expr.span,
-                        with_forced_trimmed_paths!(format!(
-                            "return type was inferred to be `{expr_ty}` here",
-                        )),
-                    );
-                    suggest_remove_deref(err, &expr);
-                }
+                let (expr_ty, expr) = if let Some((expr_ty, hir_id)) = expr_info {
+                    let expr_ty = tcx.short_ty_string(expr_ty, long_ty_file);
+                    let expr = tcx.hir().expect_expr(hir_id);
+                    (expr_ty, expr)
+                } else if let Some(body_id) = tcx.hir_node_by_def_id(body_id).body_id()
+                    && let body = tcx.hir().body(body_id)
+                    && let hir::ExprKind::Block(block, _) = body.value.kind
+                    && let Some(expr) = block.expr
+                    && let Some(expr_ty) = self
+                        .typeck_results
+                        .as_ref()
+                        .and_then(|typeck| typeck.node_type_opt(expr.hir_id))
+                    && let Some(pred) = predicate.as_clause()
+                    && let ty::ClauseKind::Trait(pred) = pred.kind().skip_binder()
+                    && self.can_eq(param_env, pred.self_ty(), expr_ty)
+                {
+                    let expr_ty = tcx.short_ty_string(expr_ty, long_ty_file);
+                    (expr_ty, expr)
+                } else {
+                    return;
+                };
+                err.span_label(
+                    expr.span,
+                    with_forced_trimmed_paths!(format!(
+                        "return type was inferred to be `{expr_ty}` here",
+                    )),
+                );
+                suggest_remove_deref(err, &expr);
             }
         }
     }

diff --git a/tests/ui/async-await/async-error-span.stderr b/tests/ui/async-await/async-error-span.stderr
@@ -3,6 +3,9 @@ error[E0277]: `()` is not a future
    |
 LL | fn get_future() -> impl Future<Output = ()> {
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^ `()` is not a future
+LL |
+LL |     panic!()
+   |     -------- return type was inferred to be `_` here
    |
    = help: the trait `Future` is not implemented for `()`
 

diff --git a/tests/ui/coroutine/arg-count-mismatch-on-unit-input.stderr b/tests/ui/coroutine/arg-count-mismatch-on-unit-input.stderr
@@ -5,7 +5,10 @@ LL | fn foo() -> impl Coroutine<u8> {
    |             ^^^^^^^^^^^^^^^^^^ expected due to this
 ...
 LL |     |_: ()| {}
-   |     ------- found signature defined here
+   |     ----------
+   |     |
+   |     found signature defined here
+   |     return type was inferred to be `{coroutine@$DIR/arg-count-mismatch-on-unit-input.rs:8:5: 8:12}` here
    |
    = note: expected coroutine signature `fn(u8) -> _`
               found coroutine signature `fn(()) -> _`

diff --git a/tests/ui/coroutine/gen_block_is_coro.stderr b/tests/ui/coroutine/gen_block_is_coro.stderr
@@ -3,18 +3,24 @@ error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:7:5: 7:8}: C
    |
 LL | fn foo() -> impl Coroutine<Yield = u32, Return = ()> {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:7:5: 7:8}`
+LL |     gen { yield 42 }
+   |     ---------------- return type was inferred to be `{gen block@$DIR/gen_block_is_coro.rs:7:5: 7:8}` here
 
 error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:11:5: 11:8}: Coroutine` is not satisfied
   --> $DIR/gen_block_is_coro.rs:10:13
    |
 LL | fn bar() -> impl Coroutine<Yield = i64, Return = ()> {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:11:5: 11:8}`
+LL |     gen { yield 42 }
+   |     ---------------- return type was inferred to be `{gen block@$DIR/gen_block_is_coro.rs:11:5: 11:8}` here
 
 error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:15:5: 15:8}: Coroutine` is not satisfied
   --> $DIR/gen_block_is_coro.rs:14:13
    |
 LL | fn baz() -> impl Coroutine<Yield = i32, Return = ()> {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:15:5: 15:8}`
+LL |     gen { yield 42 }
+   |     ---------------- return type was inferred to be `{gen block@$DIR/gen_block_is_coro.rs:15:5: 15:8}` here
 
 error: aborting due to 3 previous errors
 

diff --git a/tests/ui/coroutine/gen_block_is_no_future.stderr b/tests/ui/coroutine/gen_block_is_no_future.stderr
@@ -3,6 +3,8 @@ error[E0277]: `{gen block@$DIR/gen_block_is_no_future.rs:5:5: 5:8}` is not a fut
    |
 LL | fn foo() -> impl std::future::Future {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^ `{gen block@$DIR/gen_block_is_no_future.rs:5:5: 5:8}` is not a future
+LL |     gen { yield 42 }
+   |     ---------------- return type was inferred to be `{gen block@$DIR/gen_block_is_no_future.rs:5:5: 5:8}` here
    |
    = help: the trait `Future` is not implemented for `{gen block@$DIR/gen_block_is_no_future.rs:5:5: 5:8}`
 

diff --git a/tests/ui/coroutine/issue-88653.rs b/tests/ui/coroutine/issue-88653.rs
@@ -14,6 +14,7 @@ fn foo(bar: bool) -> impl Coroutine<(bool,)> {
     #[coroutine]
     |bar| {
         //~^ NOTE: found signature defined here
+        //~| NOTE: return type was inferred to be
         if bar {
             yield bar;
         }

diff --git a/tests/ui/coroutine/issue-88653.stderr b/tests/ui/coroutine/issue-88653.stderr
@@ -1,11 +1,21 @@
 error[E0631]: type mismatch in coroutine arguments
   --> $DIR/issue-88653.rs:8:22
    |
-LL | fn foo(bar: bool) -> impl Coroutine<(bool,)> {
-   |                      ^^^^^^^^^^^^^^^^^^^^^^^ expected due to this
+LL |   fn foo(bar: bool) -> impl Coroutine<(bool,)> {
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^ expected due to this
 ...
-LL |     |bar| {
-   |     ----- found signature defined here
+LL |       |bar| {
+   |       -----
+   |       |
+   |  _____found signature defined here
+   | |
+LL | |
+LL | |
+LL | |         if bar {
+LL | |             yield bar;
+LL | |         }
+LL | |     }
+   | |_____- return type was inferred to be `{coroutine@$DIR/issue-88653.rs:15:5: 15:10}` here
    |
    = note: expected coroutine signature `fn((bool,)) -> _`
               found coroutine signature `fn(bool) -> _`

diff --git a/...ait/diagnostics/highlight-difference-between-expected-trait-and-found-trait.svg b/...ait/diagnostics/highlight-difference-between-expected-trait-and-found-trait.svg
diff --git a/tests/ui/impl-trait/issue-55872-1.stderr b/tests/ui/impl-trait/issue-55872-1.stderr
@@ -12,6 +12,9 @@ error[E0277]: the trait bound `S: Copy` is not satisfied in `(S, T)`
    |
 LL |     fn foo<T: Default>() -> Self::E {
    |                             ^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `S`, which is required by `(S, T): Copy`
+...
+LL |         (S::default(), T::default())
+   |         ---------------------------- return type was inferred to be `(S, T)` here
    |
    = note: required because it appears within the type `(S, T)`
 help: consider further restricting this bound
@@ -24,6 +27,9 @@ error[E0277]: the trait bound `T: Copy` is not satisfied in `(S, T)`
    |
 LL |     fn foo<T: Default>() -> Self::E {
    |                             ^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `T`, which is required by `(S, T): Copy`
+...
+LL |         (S::default(), T::default())
+   |         ---------------------------- return type was inferred to be `(S, T)` here
    |
    = note: required because it appears within the type `(S, T)`
 help: consider further restricting this bound

diff --git a/tests/ui/impl-trait/issue-55872-3.stderr b/tests/ui/impl-trait/issue-55872-3.stderr
@@ -3,6 +3,9 @@ error[E0277]: the trait bound `{async block@$DIR/issue-55872-3.rs:15:9: 15:14}:
    |
 LL |     fn foo<T>() -> Self::E {
    |                    ^^^^^^^ the trait `Copy` is not implemented for `{async block@$DIR/issue-55872-3.rs:15:9: 15:14}`
+LL |
+LL |         async {}
+   |         -------- return type was inferred to be `{async block@$DIR/issue-55872-3.rs:15:9: 15:14}` here
 
 error: aborting due to 1 previous error
 

diff --git a/tests/ui/impl-trait/nested_impl_trait.stderr b/tests/ui/impl-trait/nested_impl_trait.stderr
@@ -46,7 +46,9 @@ error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfie
   --> $DIR/nested_impl_trait.rs:6:46
    |
 LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
-   |                                              ^^^^^^^^^^^^^^^^^^^^^ the trait `From<impl Into<u32>>` is not implemented for `impl Debug`, which is required by `impl Into<u32>: Into<impl Debug>`
+   |                                              ^^^^^^^^^^^^^^^^^^^^^   - return type was inferred to be `impl Into<u32>` here
+   |                                              |
+   |                                              the trait `From<impl Into<u32>>` is not implemented for `impl Debug`, which is required by `impl Into<u32>: Into<impl Debug>`
    |
    = help: the trait `Into<U>` is implemented for `T`
    = note: required for `impl Into<u32>` to implement `Into<impl Debug>`
@@ -55,7 +57,9 @@ error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfie
   --> $DIR/nested_impl_trait.rs:19:34
    |
 LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
-   |                                  ^^^^^^^^^^^^^^^^^^^^^ the trait `From<impl Into<u32>>` is not implemented for `impl Debug`, which is required by `impl Into<u32>: Into<impl Debug>`
+   |                                  ^^^^^^^^^^^^^^^^^^^^^   - return type was inferred to be `impl Into<u32>` here
+   |                                  |
+   |                                  the trait `From<impl Into<u32>>` is not implemented for `impl Debug`, which is required by `impl Into<u32>: Into<impl Debug>`
    |
    = help: the trait `Into<U>` is implemented for `T`
    = note: required for `impl Into<u32>` to implement `Into<impl Debug>`

diff --git a/tests/ui/impl-trait/opaque-cast-field-access-in-future.stderr b/tests/ui/impl-trait/opaque-cast-field-access-in-future.stderr
@@ -3,6 +3,9 @@ error[E0283]: type annotations needed
    |
 LL | fn run() -> Foo<impl Future<Output = ()>> {
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type
+LL |
+LL |     loop {}
+   |     ------- return type was inferred to be `!` here
    |
    = note: cannot satisfy `_: Future`
 

diff --git a/tests/ui/impl-trait/projection-mismatch-in-impl-where-clause.stderr b/tests/ui/impl-trait/projection-mismatch-in-impl-where-clause.stderr
@@ -3,6 +3,9 @@ error[E0271]: type mismatch resolving `<() as Super>::Assoc == ()`
    |
 LL | fn test() -> impl Test {
    |              ^^^^^^^^^ type mismatch resolving `<() as Super>::Assoc == ()`
+LL |
+LL |     ()
+   |     -- return type was inferred to be `()` here
    |
 note: expected this to be `()`
   --> $DIR/projection-mismatch-in-impl-where-clause.rs:6:18

diff --git a/tests/ui/lifetimes/lifetime-elision-return-type-trait.stderr b/tests/ui/lifetimes/lifetime-elision-return-type-trait.stderr
@@ -3,6 +3,9 @@ error[E0277]: the trait bound `Result<(), _>: Future` is not satisfied
    |
 LL | fn foo() -> impl Future<Item=(), Error=Box<dyn Error>> {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Future` is not implemented for `Result<(), _>`
+LL |
+LL |     Ok(())
+   |     ------ return type was inferred to be `Result<(), _>` here
    |
 help: this trait has no implementations, consider adding one
   --> $DIR/lifetime-elision-return-type-trait.rs:1:1

diff --git a/tests/ui/lint/issue-106991.stderr b/tests/ui/lint/issue-106991.stderr
@@ -3,6 +3,9 @@ error[E0271]: expected `foo` to be a fn item that returns `i32`, but it returns
    |
 LL | fn bar() -> impl Iterator<Item = i32> {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `()`
+...
+LL |     x.iter_mut().map(foo)
+   |     --------------------- return type was inferred to be `Map<std::slice::IterMut<'_, Vec<u8>>, for<'a> fn(&'a mut Vec<u8>) {foo}>` here
    |
    = note: required for `Map<std::slice::IterMut<'_, Vec<u8>>, for<'a> fn(&'a mut Vec<u8>) {foo}>` to implement `Iterator`
 

diff --git a/tests/ui/never_type/impl_trait_fallback2.stderr b/tests/ui/never_type/impl_trait_fallback2.stderr
@@ -3,6 +3,9 @@ error[E0277]: the trait bound `(): T` is not satisfied
    |
 LL | fn should_ret_unit() -> impl T {
    |                         ^^^^^^ the trait `T` is not implemented for `()`
+LL |
+LL |     panic!()
+   |     -------- return type was inferred to be `_` here
    |
    = help: the trait `T` is implemented for `i32`
 
@@ -11,6 +14,9 @@ error[E0277]: the trait bound `(): T` is not satisfied
    |
 LL | fn a() -> Foo {
    |           ^^^ the trait `T` is not implemented for `()`
+LL |
+LL |     panic!()
+   |     -------- return type was inferred to be `_` here
    |
    = help: the trait `T` is implemented for `i32`
 

diff --git a/tests/ui/never_type/impl_trait_fallback3.stderr b/tests/ui/never_type/impl_trait_fallback3.stderr
@@ -3,6 +3,9 @@ error[E0277]: the trait bound `(): T` is not satisfied
    |
 LL | fn a() -> Foo {
    |           ^^^ the trait `T` is not implemented for `()`
+...
+LL |     panic!()
+   |     -------- return type was inferred to be `_` here
    |
 help: this trait has no implementations, consider adding one
   --> $DIR/impl_trait_fallback3.rs:5:1

diff --git a/tests/ui/never_type/impl_trait_fallback4.stderr b/tests/ui/never_type/impl_trait_fallback4.stderr
@@ -3,6 +3,9 @@ error[E0277]: the trait bound `(): T` is not satisfied
    |
 LL | fn foo() -> impl T {
    |             ^^^^^^ the trait `T` is not implemented for `()`
+LL |
+LL |     panic!()
+   |     -------- return type was inferred to be `_` here
    |
 help: this trait has no implementations, consider adding one
   --> $DIR/impl_trait_fallback4.rs:3:1

diff --git a/tests/ui/type-alias-impl-trait/fallback.stderr b/tests/ui/type-alias-impl-trait/fallback.stderr
@@ -4,7 +4,10 @@ error[E0283]: type annotations needed
 LL | fn unconstrained_foo() -> Wrapper<Foo> {
    |                           ------------ type must be known at this point
 LL |     Wrapper::Second
-   |     ^^^^^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the enum `Wrapper`
+   |     ^^^^^^^^^^^^^^^
+   |     |
+   |     cannot infer type of the type parameter `T` declared on the enum `Wrapper`
+   |     return type was inferred to be `Wrapper<_>` here
    |
    = note: cannot satisfy `_: Copy`
 help: consider specifying the generic argument

diff --git a/tests/ui/type-alias-impl-trait/non-lifetime-binder-in-constraint.stderr b/tests/ui/type-alias-impl-trait/non-lifetime-binder-in-constraint.stderr
@@ -17,6 +17,9 @@ error[E0277]: the trait bound `{integer}: Trait<()>` is not satisfied
    |
 LL | fn produce() -> impl for<T> Trait<(), Assoc = impl Trait<T>> {
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait<()>` is not implemented for `{integer}`
+...
+LL |     16
+   |     -- return type was inferred to be `{integer}` here
    |
 help: this trait has no implementations, consider adding one
   --> $DIR/non-lifetime-binder-in-constraint.rs:4:1