Rollup merge of #137824 - estebank:rtn-sugg, r=compiler-errors

Tweak invalid RTN errors

Make suggestions verbose.

When encountering `method(type)` bound, suggest `method(..)` instead of `method()`.

```
error: argument types not allowed with return type notation
  --> $DIR/bad-inputs-and-output.rs:9:23
   |
LL | fn foo<T: Trait<method(i32): Send>>() {}
   |                       ^^^^^
   |
help: remove the input types
   |
LL - fn foo<T: Trait<method(i32): Send>>() {}
LL + fn foo<T: Trait<method(..): Send>>() {}
   |
```

When encountering both return type and arg list that isn't `..`, suggest replacing both.

```
error: return type not allowed with return type notation
  --> $DIR/bad-inputs-and-output.rs:12:25
   |
LL | fn bar<T: Trait<method() -> (): Send>>() {}
   |                         ^^^^^^
   |
help: use the right argument notation and remove the return type
   |
LL - fn bar<T: Trait<method() -> (): Send>>() {}
LL + fn bar<T: Trait<method(..): Send>>() {}
   |
```

When encountering a return type, suggest removing it including the leading whitespace.

```
error: return type not allowed with return type notation
  --> $DIR/bad-inputs-and-output.rs:24:45
   |
LL | fn bay_path<T: Trait>() where T::method(..) -> (): Send {}
   |                                             ^^^^^
   |
help: remove the return type
   |
LL - fn bay_path<T: Trait>() where T::method(..) -> (): Send {}
LL + fn bay_path<T: Trait>() where T::method(..): Send {}
   |
```

r? ``@compiler-errors``

1 files changed, 2 insertions, 1 deletions

diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index fc7a3323fc1..8d2fd595942 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -2922,8 +2922,9 @@ pub(crate) struct AddBoxNew {
 #[diag(parse_bad_return_type_notation_output)]
 pub(crate) struct BadReturnTypeNotationOutput {
     #[primary_span]
-    #[suggestion(code = "", applicability = "maybe-incorrect", style = "verbose")]
     pub span: Span,
+    #[suggestion(code = "", applicability = "maybe-incorrect", style = "verbose")]
+    pub suggestion: Span,
 }
 
 #[derive(Diagnostic)]