add trait impls to proc_macro::Ident

[Qelxiros]

ACP: rust-lang/libs-team#573

[rustbot]

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[rustbot]

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

[Qelxiros]

Clippy context: An aux crate (proc_macros.rs) was using Ident::to_string before comparing to a string literal, so I updated it to use the PartialEq implementation added in this PR.

[petrochenkov]

I suggest splitting this into one PR with (insta-stable) API changes, and then another PR with implementation optimizations.

Also, PartialEq impl for Ident was previously rejected (see #78634 and its linked issue) for the reasons that are still relevant now.
Comparisons with strings are ok, Hash is probably also ok, but not especially useful without Eq.

[Qelxiros]

To clarify, the clippy change was to fix CI.

Thanks for the context! I'd be happy to remove the PartialEq<Self> impl (and Eq, by extension) or modify it to compare spans as well if you think the rest is mergeable, or leave it as is pending further discussion. I'll also link your comment on the ACP for visibility.

[Qelxiros]

@rustbot ready

[petrochenkov]

and then another PR with implementation optimizations

This was about moving the code around and providing the optimized implementation instead of just doing .to_string().
I don't think it's necessary to add the new APIs.

The Hash impl is still questionable because it's inconsistent with the only PartialEq impl, but I'll leave this for the libs team to decide.
@rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[Qelxiros]

@petrochenkov I'm a little confused. Do you mean that this implementation should be reduced to self.to_string() == other.as_ref()? That seems to miss the point of the ACP, which was to compare Idents with Strings (and friends) without an allocation.

[petrochenkov]

Do you mean that this implementation should be reduced to self.to_string() == other.as_ref()?

Yes.
Allocation or not is an implementation detail, that can be changed at any later point without any process or team decisions.

[petrochenkov]

Did you push the changes?
I still see all the unnecessary code moving and optimizations.

[Qelxiros]

@rustbot ready

[bors]

☔ The latest upstream changes (presumably #147475) made this pull request unmergeable. Please resolve the merge conflicts.