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use implied bounds when checking opaque types

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This commit is contained in:
Ali MJ Al-Nasrawy 2022-12-22 14:36:09 +03:00
parent 4a18324a4d
commit d548747c85
7 changed files with 189 additions and 4 deletions
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17
compiler/rustc_hir_analysis/src/check/check.rs
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@ -31,6 +31,7 @@ use rustc_target::abi::FieldIdx;
use rustc_target::spec::abi::Abi;
use rustc_trait_selection::traits::error_reporting::on_unimplemented::OnUnimplementedDirective;
use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _;
use rustc_trait_selection::traits::{self, ObligationCtxt, TraitEngine, TraitEngineExt as _};
use std::ops::ControlFlow;
@ -222,7 +223,7 @@ fn check_opaque(tcx: TyCtxt<'_>, id: hir::ItemId) {
if check_opaque_for_cycles(tcx, item.owner_id.def_id, substs, span, &origin).is_err() {
return;
}
check_opaque_meets_bounds(tcx, item.owner_id.def_id, substs, span, &origin);
check_opaque_meets_bounds(tcx, item.owner_id.def_id, span, &origin);
}
/// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
@ -391,7 +392,6 @@ pub(super) fn check_opaque_for_cycles<'tcx>(
fn check_opaque_meets_bounds<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: LocalDefId,
substs: SubstsRef<'tcx>,
span: Span,
origin: &hir::OpaqueTyOrigin,
) {
@ -406,6 +406,8 @@ fn check_opaque_meets_bounds<'tcx>(
.with_opaque_type_inference(DefiningAnchor::Bind(defining_use_anchor))
.build();
let ocx = ObligationCtxt::new(&infcx);
let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
let opaque_ty = tcx.mk_opaque(def_id.to_def_id(), substs);
// `ReErased` regions appear in the "parent_substs" of closures/generators.
@ -448,9 +450,18 @@ fn check_opaque_meets_bounds<'tcx>(
match origin {
// Checked when type checking the function containing them.
hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) => {}
// Nested opaque types occur only in associated types:
// ` type Opaque<T> = impl Trait<&'static T, AssocTy = impl Nested>; `
// They can only be referenced as `<Opaque<T> as Trait<&'static T>>::AssocTy`.
// We don't have to check them here because their well-formedness follows from the WF of
// the projection input types in the defining- and use-sites.
hir::OpaqueTyOrigin::TyAlias
if tcx.def_kind(tcx.parent(def_id.to_def_id())) == DefKind::OpaqueTy => {}
// Can have different predicates to their defining use
hir::OpaqueTyOrigin::TyAlias => {
let outlives_env = OutlivesEnvironment::new(param_env);
let wf_tys = ocx.assumed_wf_types(param_env, span, def_id);
let implied_bounds = infcx.implied_bounds_tys(param_env, def_id, wf_tys);
let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds);
let _ = ocx.resolve_regions_and_report_errors(defining_use_anchor, &outlives_env);
}
}