The affected crates have had plenty of time to update.
By keeping these as lints rather than making them hard errors,
we ensure that downstream crates will still be able to compile,
even if they transitive depend on broken versions of the affected
crates.

This should hopefully discourage anyone from writing any
new code which relies on the backwards-compatibility behavior.

The equivalent for `Symbol`s was renamed some time ago (`kw::Invalid` -> `kw::Empty`), and it makes sense to do the same thing for `Ident`s.

Closes rust-lang#85526.

…esleywiser

Make all proc-macro back-compat lints deny-by-default

The affected crates have had plenty of time to update.
By keeping these as lints rather than making them hard errors,
we ensure that downstream crates will still be able to compile,
even if they transitive depend on broken versions of the affected
crates.

This should hopefully discourage anyone from writing any
new code which relies on the backwards-compatibility behavior.

resolve: Use `NameBinding` for local variables and generic parameters

`NameBinding` is a structure used for representing any name introduction (an item, or import, or even a built-in).
Except that local variables and generic parameters weren't represented as `NameBinding`s, for this reason they requires separate paths in name resolution code in several places.

This PR introduces `NameBinding`s for local variables as well and simplifies all the code working with them leaving only the `NameBinding` paths.

…-mut, r=petrochenkov

Fix ICE with `let...else` and `ref mut`

Fixes rust-lang#89960, opened for review.
I'm not satisfied with the current diagnostics, any ideas?

Nicer error message if the user attempts to do let...else if

Gives a nice "conditional `else if` is not supported for `let...else`" error when encountering a `let...else if` pattern, as suggested in the [let...else tracking issue](rust-lang#87335 (comment)).

…c, r=GuillaumeGomez

Check implementing type for `#[doc(hidden)]`

Closes rust-lang#85526.

rustc_span: `Ident::invalid` -> `Ident::empty`

The equivalent for `Symbol`s was renamed some time ago (`kw::Invalid` -> `kw::Empty`), and it makes sense to do the same thing for `Ident`s as well.