bjoernager/rust
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Teach typeck/borrowck/solvers how to deal with async closures

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This commit is contained in:
Michael Goulet 2024-01-24 22:27:25 +00:00
parent c567eddec2
commit a82bae2172
35 changed files with 1221 additions and 66 deletions
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50
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
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@ -83,6 +83,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplSource::Builtin(BuiltinImplSource::Misc, vtable_closure)
}
AsyncClosureCandidate => {
let vtable_closure = self.confirm_async_closure_candidate(obligation)?;
ImplSource::Builtin(BuiltinImplSource::Misc, vtable_closure)
}
AsyncFnKindHelperCandidate => ImplSource::Builtin(BuiltinImplSource::Misc, vec![]),
CoroutineCandidate => {
let vtable_coroutine = self.confirm_coroutine_candidate(obligation)?;
ImplSource::Builtin(BuiltinImplSource::Misc, vtable_coroutine)
@ -869,6 +876,49 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
Ok(nested)
}
#[instrument(skip(self), level = "debug")]
fn confirm_async_closure_candidate(
&mut self,
obligation: &PolyTraitObligation<'tcx>,
) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
// Okay to skip binder because the args on closure types never
// touch bound regions, they just capture the in-scope
// type/region parameters.
let self_ty = self.infcx.shallow_resolve(obligation.self_ty().skip_binder());
let ty::CoroutineClosure(closure_def_id, args) = *self_ty.kind() else {
bug!("async closure candidate for non-coroutine-closure {:?}", obligation);
};
let trait_ref = args.as_coroutine_closure().coroutine_closure_sig().map_bound(|sig| {
ty::TraitRef::new(
self.tcx(),
obligation.predicate.def_id(),
[self_ty, sig.tupled_inputs_ty],
)
});
let mut nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
let goal_kind =
self.tcx().async_fn_trait_kind_from_def_id(obligation.predicate.def_id()).unwrap();
nested.push(obligation.with(
self.tcx(),
ty::TraitRef::from_lang_item(
self.tcx(),
LangItem::AsyncFnKindHelper,
obligation.cause.span,
[
args.as_coroutine_closure().kind_ty(),
Ty::from_closure_kind(self.tcx(), goal_kind),
],
),
));
debug!(?closure_def_id, ?trait_ref, ?nested, "confirm closure candidate obligations");
Ok(nested)
}
/// In the case of closure types and fn pointers,
/// we currently treat the input type parameters on the trait as
/// outputs. This means that when we have a match we have only