Add correct suggestion for multi-references for self type in method

[Kivooeo]

Currently the suggestion for this code

fn main() {}

struct A {
    field: i32,
}

impl A {
    fn f(&&self) {}
}

looks like this, which is incorrect and missleading

   Compiling playground v0.0.1 (/playground)
error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `:`, `{`, or `|`, found `)`
 --> src/main.rs:8:16
  |
8 |     fn f(&&self) {}
  |                ^ expected one of 9 possible tokens
  |
  = note: anonymous parameters are removed in the 2018 edition (see RFC 1685)
help: explicitly ignore the parameter name
  |
8 |     fn f(_: &&self) {}
  |          ++

So this fixes it and make more correct suggestions

error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `:`, `{`, or `|`, found `)`
 --> /home/gh-Kivooeo/test_/src/main.rs:8:16
  |
8 |     fn f(&&self) {}
  |                ^ expected one of 9 possible tokens
  |
help: `self` should be `self`, `&self` or `&mut self`, please remove extra references
  |
8 -     fn f(&&self) {}
8 +     fn f(&self) {}

Implementation is pretty self-documenting, but if you have suggestions on how to improve this (according to current test, which may be not fully covering all cases, this is works very well) or have some funny edge cases to show, I would appreciate it

r? compiler

[petrochenkov]

I'm not sure if it's useful to give a special suggestion for this.
I guess &&self specifically is possible in practice as a typo, but anything more than that, especially intentionally? Very unlikely.
@rustbot author

[Kivooeo]

Let's try this one, I removed second suggestion with self: Self

Not sure what to do with cases where there is more than two references, but I'd keep it as it just because current suggestion is even worse and not correct in any way

[Kivooeo]

r? compiler

[JonathanBrouwer]

@rustbot author

[rustbot]

⚠️ Warning ⚠️

• This PR is based on an upstream commit that is older than 28 days.

  It's recommended to update your branch according to the rustc-dev-guide.

[JonathanBrouwer]

r=me after rebasing & ci green

[Kivooeo]

Forget about rebase but I guess it shouldn't be a problem?

[JonathanBrouwer]

There's an increased risk of soft-conflicts if you have an old base, but given how isolated this change is it should be fine.
@bors r+ rollup

[bors]

📌 Commit 7298174 has been approved by JonathanBrouwer

It is now in the queue for this repository.