E0311 for `impl Trait` parameter type suggests invalid syntax

[AnthonyMikh]

Given the following code:

fn foo(d: impl Sized, p: &mut ()) -> impl Sized + '_ {
    (d, p)
}

The current output is:

error[E0311]: the parameter type `impl Sized` may not live long enough
 --> src/lib.rs:2:5
  |
2 |     (d, p)
  |     ^^^^^^
  |
note: the parameter type `impl Sized` must be valid for the anonymous lifetime defined here...
 --> src/lib.rs:1:26
  |
1 | fn foo(d: impl Sized, p: &mut ()) -> impl Sized + '_ {
  |                          ^^^^^^^
note: ...so that the type `impl Sized` will meet its required lifetime bounds
 --> src/lib.rs:2:5
  |
2 |     (d, p)
  |     ^^^^^^
help: consider adding an explicit lifetime bound...
  |
1 | fn foo(d: 'a, impl Sized + 'a, p: &mut ()) -> impl Sized + '_ {

Not only the suggested syntax is invalid, it also suggests introducing a fresh lifetime parameter instead of naming the elided one on p.

Ping @estebank.

@rustbot modify labels: +A-suggestion-diagnostics +D-invalid-suggestion

[yanchen4791]

@rustbot claim