Add suggestions for must_implement_one_of

[joshtriplett]

As with the suggestions for mandatory trait methods, provide suggestions for must_implement_one_of, which include the signatures of the trait methods. This makes it easy to copy-paste the signatures into the impl block.

Invoke the same logic from check_drop_xor_pin_drop, to provide suggestions with the signatures of drop and pin_drop.

Using #106643 (read/read_buf) as an example, without this change, the diagnostics look like this:

error[E0046]: not all trait items implemented, missing one of: `read`, `read_buf`
 --> src/main.rs:3:1
  |
3 | impl std::io::Read for R {
  | ^^^^^^^^^^^^^^^^^^^^^^^^ missing one of `read`, `read_buf` in implementation

For more information about this error, try `rustc --explain E0046`.

With this change, they include suggestions:

error[E0046]: not all trait items implemented, missing one of: `read`, `read_buf`
 --> src/main.rs:3:1
  |
3 | impl std::io::Read for R {
  | ^^^^^^^^^^^^^^^^^^^^^^^^ missing one of `read`, `read_buf` in implementation
  |
  = help: implement the missing item: `fn read(&mut self, _: &mut [u8]) -> Result<usize, std::io::Error> { todo!() }`
  = help: implement the missing item: `fn read_buf(&mut self, _: BorrowedCursor<'_, u8>) -> Result<(), std::io::Error> { todo!() }`

For more information about this error, try `rustc --explain E0046`.

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[mejrs]

r? me

Thanks, great idea.

Can you also add a rustfix test?

View changes since this review

[mejrs]

This should be correct now

Suggested change

	applicability = "machine-applicable"

[joshtriplett]

Technically the inserted suggestions would compile, but would definitively make the code incorrect, because they include todo!() placeholders in them. So, unless I'm misunderstanding, I don't think these qualify as machine-applicable.