Point to where missing return type should go

Author: compiler-errors

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -1188,7 +1188,7 @@ fn report_trait_method_mismatch<'tcx>(
                     let ap = Applicability::MachineApplicable;
                     match sig.decl.output {
                         hir::FnRetTy::DefaultReturn(sp) => {
-                            let sugg = format!("-> {} ", trait_sig.output());
+                            let sugg = format!(" -> {}", trait_sig.output());
                             diag.span_suggestion_verbose(sp, msg, sugg, ap);
                         }
                         hir::FnRetTy::Return(hir_ty) => {

compiler/rustc_hir_typeck/src/errors.rs

@@ -110,7 +110,7 @@ pub struct AddressOfTemporaryTaken {
 pub enum AddReturnTypeSuggestion {
     #[suggestion(
         hir_typeck_add_return_type_add,
-        code = "-> {found} ",
+        code = " -> {found}",
         applicability = "machine-applicable"
     )]
     Add {
@@ -120,7 +120,7 @@ pub enum AddReturnTypeSuggestion {
     },
     #[suggestion(
         hir_typeck_add_return_type_missing_here,
-        code = "-> _ ",
+        code = " -> _",
         applicability = "has-placeholders"
     )]
     MissingHere {

compiler/rustc_infer/src/errors/mod.rs

@@ -194,13 +194,13 @@ impl<'a> SourceKindMultiSuggestion<'a> {
         data: &'a FnRetTy<'a>,
         should_wrap_expr: Option<Span>,
     ) -> Self {
-        let (arrow, post) = match data {
-            FnRetTy::DefaultReturn(_) => ("-> ", " "),
-            _ => ("", ""),
+        let arrow = match data {
+            FnRetTy::DefaultReturn(_) => " -> ",
+            _ => "",
         };
         let (start_span, start_span_code, end_span) = match should_wrap_expr {
-            Some(end_span) => (data.span(), format!("{arrow}{ty_info}{post}{{ "), Some(end_span)),
-            None => (data.span(), format!("{arrow}{ty_info}{post}"), None),
+            Some(end_span) => (data.span(), format!("{arrow}{ty_info} {{"), Some(end_span)),
+            None => (data.span(), format!("{arrow}{ty_info}"), None),
         };
         Self::ClosureReturn { start_span, start_span_code, end_span }
     }

compiler/rustc_parse/src/parser/ty.rs

@@ -247,7 +247,7 @@ impl<'a> Parser<'a> {
             )?;
             FnRetTy::Ty(ty)
         } else {
-            FnRetTy::Default(self.token.span.shrink_to_lo())
+            FnRetTy::Default(self.prev_token.span.shrink_to_hi())
         })
     }
 

tests/ui/associated-type-bounds/issue-71443-1.stderr

@@ -2,7 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-71443-1.rs:6:5
    |
 LL | fn hello<F: for<'a> Iterator<Item: 'a>>() {
-   |                                           - help: try adding a return type: `-> Incorrect`
+   |                                          - help: try adding a return type: `-> Incorrect`
 LL |     Incorrect
    |     ^^^^^^^^^ expected `()`, found `Incorrect`
 

tests/ui/async-await/async-await-let-else.stderr

@@ -22,7 +22,7 @@ error[E0277]: `Rc<()>` cannot be sent between threads safely
   --> $DIR/async-await-let-else.rs:47:13
    |
 LL | async fn foo2(x: Option<bool>) {
-   |                                - within this `impl Future<Output = ()>`
+   |                               - within this `impl Future<Output = ()>`
 ...
 LL |     is_send(foo2(Some(true)));
    |     ------- ^^^^^^^^^^^^^^^^ `Rc<()>` cannot be sent between threads safely

tests/ui/async-await/issue-64130-3-other.stderr

@@ -2,7 +2,7 @@ error[E0277]: the trait bound `Foo: Qux` is not satisfied in `impl Future<Output
   --> $DIR/issue-64130-3-other.rs:25:12
    |
 LL | async fn bar() {
-   |                - within this `impl Future<Output = ()>`
+   |               - within this `impl Future<Output = ()>`
 ...
 LL |     is_qux(bar());
    |            ^^^^^ within `impl Future<Output = ()>`, the trait `Qux` is not implemented for `Foo`

tests/ui/async-await/issues/issue-67893.stderr

@@ -6,10 +6,10 @@ LL |     g(issue_67893::run())
    |     |
    |     required by a bound introduced by this call
    |
-  ::: $DIR/auxiliary/issue_67893.rs:9:20
+  ::: $DIR/auxiliary/issue_67893.rs:9:19
    |
 LL | pub async fn run() {
-   |                    - within this `impl Future<Output = ()>`
+   |                   - within this `impl Future<Output = ()>`
    |
    = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `MutexGuard<'_, ()>`
    = note: required because it captures the following types: `Arc<Mutex<()>>`, `MutexGuard<'_, ()>`, `impl Future<Output = ()>`

tests/ui/async-await/mutually-recursive-async-impl-trait-type.stderr

@@ -1,17 +1,17 @@
 error[E0733]: recursion in an `async fn` requires boxing
-  --> $DIR/mutually-recursive-async-impl-trait-type.rs:5:18
+  --> $DIR/mutually-recursive-async-impl-trait-type.rs:5:17
    |
 LL | async fn rec_1() {
-   |                  ^ recursive `async fn`
+   |                 ^ recursive `async fn`
    |
    = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
    = note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion
 
 error[E0733]: recursion in an `async fn` requires boxing
-  --> $DIR/mutually-recursive-async-impl-trait-type.rs:9:18
+  --> $DIR/mutually-recursive-async-impl-trait-type.rs:9:17
    |
 LL | async fn rec_2() {
-   |                  ^ recursive `async fn`
+   |                 ^ recursive `async fn`
    |
    = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`
    = note: consider using the `async_recursion` crate: https://crates.io/crates/async_recursion

tests/ui/async-await/partial-drop-partial-reinit.stderr

@@ -7,7 +7,7 @@ LL |     gimme_send(foo());
    |     required by a bound introduced by this call
 ...
 LL | async fn foo() {
-   |                - within this `impl Future<Output = ()>`
+   |               - within this `impl Future<Output = ()>`
    |
    = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `NotSend`
    = note: required because it appears within the type `(NotSend,)`