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Auto merge of #75443 - lcnr:opaque-normalize, r=nikomatsakis

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allow escaping bound vars when normalizing `ty::Opaque`

implements https://github.com/rust-lang/rust/issues/75313#issuecomment-672216146 and fixes #75313

cc @eddyb @RalfJung

r? @nikomatsakis
This commit is contained in:
bors 2020-08-13 15:03:40 +00:00
commit 0a49057dd3
3 changed files with 17 additions and 9 deletions
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7
src/librustc_trait_selection/traits/project.rs
View File

@ -324,8 +324,7 @@ impl<'a, 'b, 'tcx> TypeFolder<'tcx> for AssocTypeNormalizer<'a, 'b, 'tcx> {
let ty = ty.super_fold_with(self);
match ty.kind {
ty::Opaque(def_id, substs) if !substs.has_escaping_bound_vars() => {
// (*)
ty::Opaque(def_id, substs) => {
// Only normalize `impl Trait` after type-checking, usually in codegen.
match self.param_env.reveal() {
Reveal::UserFacing => ty,
@ -353,9 +352,7 @@ impl<'a, 'b, 'tcx> TypeFolder<'tcx> for AssocTypeNormalizer<'a, 'b, 'tcx> {
}
ty::Projection(ref data) if !data.has_escaping_bound_vars() => {
// (*)
// (*) This is kind of hacky -- we need to be able to
// This is kind of hacky -- we need to be able to
// handle normalization within binders because
// otherwise we wind up a need to normalize when doing
// trait matching (since you can have a trait

6
src/librustc_trait_selection/traits/query/normalize.rs
View File

@ -101,8 +101,7 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for QueryNormalizer<'cx, 'tcx> {
let ty = ty.super_fold_with(self);
match ty.kind {
ty::Opaque(def_id, substs) if !substs.has_escaping_bound_vars() => {
// (*)
ty::Opaque(def_id, substs) => {
// Only normalize `impl Trait` after type-checking, usually in codegen.
match self.param_env.reveal() {
Reveal::UserFacing => ty,
@ -140,8 +139,7 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for QueryNormalizer<'cx, 'tcx> {
}
ty::Projection(ref data) if !data.has_escaping_bound_vars() => {
// (*)
// (*) This is kind of hacky -- we need to be able to
// This is kind of hacky -- we need to be able to
// handle normalization within binders because
// otherwise we wind up a need to normalize when doing
// trait matching (since you can have a trait

13
src/test/ui/mir/issue-75419-validation-impl-trait.rs Normal file
View File

@ -0,0 +1,13 @@
// build-pass
// This used to fail MIR validation due to the types on both sides of
// an assignment not being equal.
// The failure doesn't occur with a check-only build.
fn iter_slice<'a, T>(xs: &'a [T]) -> impl Iterator<Item = &'a T> {
xs.iter()
}
fn main() {
iter_slice::<()> as fn(_) -> _;
}