OpaqueTypeCollector missing CoroutineClosure, async closure def_ids not collected

[SebTardif]

Bug

OpaqueTypeCollector in compiler/rustc_hir_analysis/src/check/check.rs:2199 matches ty::Closure(def_id, ..) | ty::Coroutine(def_id, ..) but is missing ty::CoroutineClosure(def_id, ..).

When an async closure (stable since Rust 1.85) contains references to opaque types, the CoroutineClosure TyKind variant falls through to the default _ => t.super_visit_with(self) arm instead of being pushed onto self.closures. This means the closure def_id is not collected, potentially causing missed opaque type checks for async closures.

Code at fault

// check.rs:2199
ty::Closure(def_id, ..) | ty::Coroutine(def_id, ..) => {
    self.closures.push(def_id);
    t.super_visit_with(self);
}

Missing: ty::CoroutineClosure(def_id, ..)

Pattern

Same CoroutineClosure-missing-from-match pattern as #477, #478, #479. The CoroutineClosure TyKind variant was added for async closures but many match sites were not updated.

Severity

Diagnostic-only. The closures list is used for opaque type diagnostics, so the impact is limited to potentially missing or incorrect error messages when async closures interact with opaque types.

[SebTardif]

Fix PR: #577