borrowck: mutability and use-while-moved diagnostics miss ty::CoroutineClosure

[SebTardif]

Summary

Several borrowck diagnostic paths only pattern-match ty::Closure, so async/coroutine closures (ty::CoroutineClosure) get weaker or missing help:

1. mutability_errors.rs – mutating an upvar only calls show_mutating_upvar when the place type is ty::Closure (two sites: direct local and via ty::Ref(_, ty, Mut)).
2. conflict_errors.rs – needs_note suppresses the generic move note only for ty::Closure with a closure_kind_origin; coroutine closures always get the extra note even when a better origin note applies.

Related paths were already fixed in describe_field / moved-or-invoked notes (issue/PR cluster around #576 / #569).

Origin

Audit of incomplete CoroutineClosure match arms in borrowck diagnostics, SebTardif/rust fork of rust-lang/rust.

Affected code (upstream tip at audit time)

https://github.com/rust-lang/rust/blob/f28ac764c36/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs#L468-L470

https://github.com/rust-lang/rust/blob/f28ac764c36/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs#L521-L525

https://github.com/rust-lang/rust/blob/f28ac764c36/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs#L276-L281

Suggested fix

Use ty::Closure(id, _) | ty::CoroutineClosure(id, _) in all three sites (same pattern as PR #576 on diagnostics/mod.rs).

Impact

Low. Wrong/missing suggestions and notes for async-closure borrow errors, not incorrect accept/reject of programs.

Related

• diagnostics: missing CoroutineClosure in fulfillment span adjust and explain_borrow destructor #569 (fulfillment/explain_borrow CoroutineClosure)
• borrowck: handle CoroutineClosure in describe_field and moved-closure notes #576 (moved/invoked + describe_field)