suggest adding parameters to exactly match the trait definition

[lyming2007]

when the impl of the function doesn't match with the trait declaration
this will fix #106999

[rustbot]

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[compiler-errors]

What happened here?

[lyming2007]

oh. That's a bug of my implementation which doesn't consider the impl function being 0 parameters. I'll fix it

[compiler-errors]

This just copies the contents of the parentheses, right? If so, this doesn't take params into account, I think:

trait Foo {
  fn bar<T>(_: T);
}

impl Foo for () {
  fn bar<E>(_: E, _: i32) {}
}

which would suggest changing fn bar<E>(_: T) {}

[lyming2007]

yes it would suggest:

error[E0050]: method `bar` has 2 parameters but the declaration in trait `Foo::bar` has 1
 --> params.rs:6:16
  |
2 |   fn bar<T>(_: T);
  |                - trait requires 1 parameter
...
6 |   fn bar<E>(_: E, _: i32) {}
  |                ^^^^^^^^^ expected 1 parameter, found 2
  |
help: modify the signature to match the trait definition
  |
6 |   fn bar<E>(_: T) {}

I think we should suggest it to be fn bar<E>(_: E) {} or fn bar<T>(_: T) {}

[compiler-errors]

Similarly, we need to consider cases where the arguments reference generics from the trait:

trait Foo<T> {
  fn foo(_: T);
}

impl Foo<()> for i32 {
  fn foo();
}

Should suggest _: (), not _: T.

[compiler-errors]

Gonna mark this as waiting on author. Feel free to ping me for advice, and use @rustbot ready to mark this as ready for review.

r? @compiler-errors
@rustbot author

[JohnCSimon]

@lyming2007
ping from triage - can you post your status on this PR? There hasn't been an update in a few months. Thanks!

FYI: when a PR is ready for review, send a message containing
@rustbot ready to switch to S-waiting-on-review so the PR is in the reviewer's backlog.

[Dylan-DPC]

Closing this as inactive. Feel free to reöpen this pr or create a new pr if you get the time to work on this. Thanks