rustc_public: CoroutineClosure types todo! in stable SMIR conversion

[SebTardif]

Bug

compiler/rustc_public/src/unstable/convert/stable/ty.rs lowers ty::Closure and ty::Coroutine to RigidTy, but ty::CoroutineClosure hits:

ty::CoroutineClosure(..) => todo!("FIXME(async_closures): Lower these to SMIR"),

RigidTy::CoroutineClosure, CoroutineClosureDef, and tables.coroutine_closure_def already exist (MIR aggregate lowering and internal conversion already handle this variant).

Origin

Introduced when async closures landed as TyKind::CoroutineClosure:

rust-lang@c567edd

SMIR todo stub added in:

rust-lang@881b6b5

Impact

Any rustc_public/SMIR consumer that encounters an async closure type ICE via todo!.

Fix

Mirror the Closure/Coroutine arms using tables.coroutine_closure_def and RigidTy::CoroutineClosure.