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only instantiate opaques with rigid types

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This commit is contained in:
lcnr 2023-11-09 11:03:28 +01:00
parent 1f12f1cc83
commit 1c54494888
2 changed files with 22 additions and 17 deletions
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18
compiler/rustc_trait_selection/src/solve/mod.rs
View File

@ -312,26 +312,10 @@ fn try_normalize_ty_recur(
return None;
}
let ty::Alias(kind, projection_ty) = *ty.kind() else {
let ty::Alias(_, projection_ty) = *ty.kind() else {
return Some(ty);
};
// We do no always define opaque types eagerly to allow non-defining uses in the defining scope.
if let (DefineOpaqueTypes::No, ty::AliasKind::Opaque) = (define_opaque_types, kind) {
if let Some(def_id) = projection_ty.def_id.as_local() {
if self
.unify_existing_opaque_tys(
param_env,
OpaqueTypeKey { def_id, args: projection_ty.args },
self.next_ty_infer(),
)
.is_empty()
{
return Some(ty);
}
}
}
// FIXME(@lcnr): If the normalization of the alias adds an inference constraint which
// causes a previously added goal to fail, then we treat the alias as rigid.
//

21
compiler/rustc_trait_selection/src/solve/project_goals/opaques.rs
View File

@ -44,6 +44,10 @@ pub(super) fn normalize_opaque_type(
// Prefer opaques registered already.
let opaque_type_key =
ty::OpaqueTypeKey { def_id: opaque_ty_def_id, args: opaque_ty.args };
// FIXME: This also unifies the previous hidden type with the expected.
//
// If that fails, we insert `expected` as a new hidden type instead of
// eagerly emitting an error.
let matches =
self.unify_existing_opaque_tys(goal.param_env, opaque_type_key, expected);
if !matches.is_empty() {
@ -53,6 +57,23 @@ pub(super) fn normalize_opaque_type(
return self.flounder(&matches);
}
}
let expected = match self.try_normalize_ty(goal.param_env, expected) {
Some(ty) => {
if ty.is_ty_var() {
return self.evaluate_added_goals_and_make_canonical_response(
Certainty::AMBIGUOUS,
);
} else {
ty
}
}
None => {
return self
.evaluate_added_goals_and_make_canonical_response(Certainty::OVERFLOW);
}
};
// Otherwise, define a new opaque type
self.insert_hidden_type(opaque_type_key, goal.param_env, expected)?;
self.add_item_bounds_for_hidden_type(