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Rollup merge of #103008 - aliemjay:opaque-parent-substs, r=oli-obk

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replace ReErased with fresh region vars in opaque types

See inline comments.

Prior art #102943. cc ``@compiler-errors`` ``@oli-obk``

Fixes #100267
Fixes #101940
Fixes #102649
Fixes #102510
This commit is contained in:
Matthias Krüger 2022-10-14 00:45:18 +02:00 • committed by GitHub
commit 059bbf7ea9
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4 changed files with 209 additions and 5 deletions
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20
compiler/rustc_hir_analysis/src/check/check.rs
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@ -732,8 +732,6 @@ fn check_opaque_meets_bounds<'tcx>(
span: Span,
origin: &hir::OpaqueTyOrigin,
) {
let hidden_type = tcx.bound_type_of(def_id.to_def_id()).subst(tcx, substs);
let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
let defining_use_anchor = match *origin {
hir::OpaqueTyOrigin::FnReturn(did) | hir::OpaqueTyOrigin::AsyncFn(did) => did,
@ -748,14 +746,26 @@ fn check_opaque_meets_bounds<'tcx>(
let ocx = ObligationCtxt::new(&infcx);
let opaque_ty = tcx.mk_opaque(def_id.to_def_id(), substs);
// `ReErased` regions appear in the "parent_substs" of closures/generators.
// We're ignoring them here and replacing them with fresh region variables.
// See tests in ui/type-alias-impl-trait/closure_{parent_substs,wf_outlives}.rs.
//
// FIXME: Consider wrapping the hidden type in an existential `Binder` and instantiating it
// here rather than using ReErased.
let hidden_ty = tcx.bound_type_of(def_id.to_def_id()).subst(tcx, substs);
let hidden_ty = tcx.fold_regions(hidden_ty, |re, _dbi| match re.kind() {
ty::ReErased => infcx.next_region_var(RegionVariableOrigin::MiscVariable(span)),
_ => re,
});
let misc_cause = traits::ObligationCause::misc(span, hir_id);
match infcx.at(&misc_cause, param_env).eq(opaque_ty, hidden_type) {
match infcx.at(&misc_cause, param_env).eq(opaque_ty, hidden_ty) {
Ok(infer_ok) => ocx.register_infer_ok_obligations(infer_ok),
Err(ty_err) => {
tcx.sess.delay_span_bug(
span,
&format!("could not unify `{hidden_type}` with revealed type:\n{ty_err}"),
&format!("could not unify `{hidden_ty}` with revealed type:\n{ty_err}"),
);
}
}
@ -764,7 +774,7 @@ fn check_opaque_meets_bounds<'tcx>(
// Defining use functions may have more bounds than the opaque type, which is ok, as long as the
// hidden type is well formed even without those bounds.
let predicate =
ty::Binder::dummy(ty::PredicateKind::WellFormed(hidden_type.into())).to_predicate(tcx);
ty::Binder::dummy(ty::PredicateKind::WellFormed(hidden_ty.into())).to_predicate(tcx);
ocx.register_obligation(Obligation::new(misc_cause, param_env, predicate));
// Check that all obligations are satisfied by the implementation's