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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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182
compiler/rustc_trait_selection/src/traits/project.rs
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@ -1833,10 +1833,28 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
lang_items.fn_trait(),
lang_items.fn_mut_trait(),
lang_items.fn_once_trait(),
lang_items.async_fn_trait(),
lang_items.async_fn_mut_trait(),
lang_items.async_fn_once_trait(),
].contains(&Some(trait_ref.def_id))
{
true
}else if lang_items.discriminant_kind_trait() == Some(trait_ref.def_id) {
} else if lang_items.async_fn_kind_helper() == Some(trait_ref.def_id) {
// FIXME(async_closures): Validity constraints here could be cleaned up.
if obligation.predicate.args.type_at(0).is_ty_var()
|| obligation.predicate.args.type_at(4).is_ty_var()
|| obligation.predicate.args.type_at(5).is_ty_var()
{
candidate_set.mark_ambiguous();
true
} else if obligation.predicate.args.type_at(0).to_opt_closure_kind().is_some()
&& obligation.predicate.args.type_at(1).to_opt_closure_kind().is_some()
{
true
} else {
false
}
} else if lang_items.discriminant_kind_trait() == Some(trait_ref.def_id) {
match self_ty.kind() {
ty::Bool
| ty::Char
@ -2061,6 +2079,10 @@ fn confirm_select_candidate<'cx, 'tcx>(
} else {
confirm_fn_pointer_candidate(selcx, obligation, data)
}
} else if selcx.tcx().async_fn_trait_kind_from_def_id(trait_def_id).is_some() {
confirm_async_closure_candidate(selcx, obligation, data)
} else if lang_items.async_fn_kind_helper() == Some(trait_def_id) {
confirm_async_fn_kind_helper_candidate(selcx, obligation, data)
} else {
confirm_builtin_candidate(selcx, obligation, data)
}
@ -2421,6 +2443,164 @@ fn confirm_callable_candidate<'cx, 'tcx>(
confirm_param_env_candidate(selcx, obligation, predicate, true)
}
fn confirm_async_closure_candidate<'cx, 'tcx>(
selcx: &mut SelectionContext<'cx, 'tcx>,
obligation: &ProjectionTyObligation<'tcx>,
mut nested: Vec<PredicateObligation<'tcx>>,
) -> Progress<'tcx> {
let self_ty = selcx.infcx.shallow_resolve(obligation.predicate.self_ty());
let ty::CoroutineClosure(def_id, args) = *self_ty.kind() else {
unreachable!(
"expected coroutine-closure self type for coroutine-closure candidate, found {self_ty}"
)
};
let args = args.as_coroutine_closure();
let kind_ty = args.kind_ty();
let tcx = selcx.tcx();
let goal_kind =
tcx.async_fn_trait_kind_from_def_id(obligation.predicate.trait_def_id(tcx)).unwrap();
let helper_trait_def_id = tcx.require_lang_item(LangItem::AsyncFnKindHelper, None);
nested.push(obligation.with(
tcx,
ty::TraitRef::new(
tcx,
helper_trait_def_id,
[kind_ty, Ty::from_closure_kind(tcx, goal_kind)],
),
));
let env_region = match goal_kind {
ty::ClosureKind::Fn | ty::ClosureKind::FnMut => obligation.predicate.args.region_at(2),
ty::ClosureKind::FnOnce => tcx.lifetimes.re_static,
};
// FIXME(async_closures): Make this into a lang item.
let upvars_projection_def_id =
tcx.associated_items(helper_trait_def_id).in_definition_order().next().unwrap().def_id;
// FIXME(async_closures): Confirmation is kind of a mess here. Ideally,
// we'd short-circuit when we know that the goal_kind >= closure_kind, and not
// register a nested predicate or create a new projection ty here. But I'm too
// lazy to make this more efficient atm, and we can always tweak it later,
// since all this does is make the solver do more work.
//
// The code duplication due to the different length args is kind of weird, too.
let poly_cache_entry = args.coroutine_closure_sig().map_bound(|sig| {
let (projection_ty, term) = match tcx.item_name(obligation.predicate.def_id) {
sym::CallOnceFuture => {
let tupled_upvars_ty = Ty::new_projection(
tcx,
upvars_projection_def_id,
[
ty::GenericArg::from(kind_ty),
Ty::from_closure_kind(tcx, goal_kind).into(),
env_region.into(),
sig.tupled_inputs_ty.into(),
args.tupled_upvars_ty().into(),
args.coroutine_captures_by_ref_ty().into(),
],
);
let coroutine_ty = sig.to_coroutine(
tcx,
args.parent_args(),
tcx.coroutine_for_closure(def_id),
tupled_upvars_ty,
);
(
ty::AliasTy::new(
tcx,
obligation.predicate.def_id,
[self_ty, sig.tupled_inputs_ty],
),
coroutine_ty.into(),
)
}
sym::CallMutFuture | sym::CallFuture => {
let tupled_upvars_ty = Ty::new_projection(
tcx,
upvars_projection_def_id,
[
ty::GenericArg::from(kind_ty),
Ty::from_closure_kind(tcx, goal_kind).into(),
env_region.into(),
sig.tupled_inputs_ty.into(),
args.tupled_upvars_ty().into(),
args.coroutine_captures_by_ref_ty().into(),
],
);
let coroutine_ty = sig.to_coroutine(
tcx,
args.parent_args(),
tcx.coroutine_for_closure(def_id),
tupled_upvars_ty,
);
(
ty::AliasTy::new(
tcx,
obligation.predicate.def_id,
[
ty::GenericArg::from(self_ty),
sig.tupled_inputs_ty.into(),
env_region.into(),
],
),
coroutine_ty.into(),
)
}
sym::Output => (
ty::AliasTy::new(tcx, obligation.predicate.def_id, [self_ty, sig.tupled_inputs_ty]),
sig.return_ty.into(),
),
name => bug!("no such associated type: {name}"),
};
ty::ProjectionPredicate { projection_ty, term }
});
confirm_param_env_candidate(selcx, obligation, poly_cache_entry, true)
.with_addl_obligations(nested)
}
fn confirm_async_fn_kind_helper_candidate<'cx, 'tcx>(
selcx: &mut SelectionContext<'cx, 'tcx>,
obligation: &ProjectionTyObligation<'tcx>,
nested: Vec<PredicateObligation<'tcx>>,
) -> Progress<'tcx> {
let [
// We already checked that the goal_kind >= closure_kind
_closure_kind_ty,
goal_kind_ty,
borrow_region,
tupled_inputs_ty,
tupled_upvars_ty,
coroutine_captures_by_ref_ty,
] = **obligation.predicate.args
else {
bug!();
};
let predicate = ty::ProjectionPredicate {
projection_ty: ty::AliasTy::new(
selcx.tcx(),
obligation.predicate.def_id,
obligation.predicate.args,
),
term: ty::CoroutineClosureSignature::tupled_upvars_by_closure_kind(
selcx.tcx(),
goal_kind_ty.expect_ty().to_opt_closure_kind().unwrap(),
tupled_inputs_ty.expect_ty(),
tupled_upvars_ty.expect_ty(),
coroutine_captures_by_ref_ty.expect_ty(),
borrow_region.expect_region(),
)
.into(),
};
confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false)
.with_addl_obligations(nested)
}
fn confirm_param_env_candidate<'cx, 'tcx>(
selcx: &mut SelectionContext<'cx, 'tcx>,
obligation: &ProjectionTyObligation<'tcx>,