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Don't normalize opaque types with escaping late-bound regions #89285

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Sep 27, 2021
Merged

Don't normalize opaque types with escaping late-bound regions #89285

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8 changes: 4 additions & 4 deletions compiler/rustc_trait_selection/src/traits/project.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -388,15 +388,15 @@ impl<'a, 'b, 'tcx> TypeFolder<'tcx> for AssocTypeNormalizer<'a, 'b, 'tcx> {
// to make sure we don't forget to fold the substs regardless.

match *ty.kind() {
ty::Opaque(def_id, substs) => {
// This is really important. While we *can* handle this, this has
// severe performance implications for large opaque types with
// late-bound regions. See `issue-88862` benchmark.
ty::Opaque(def_id, substs) if !substs.has_escaping_bound_vars() => {
// Only normalize `impl Trait` after type-checking, usually in codegen.
match self.param_env.reveal() {
Reveal::UserFacing => ty.super_fold_with(self),

Reveal::All => {
// N.b. there is an assumption here all this code can handle
// escaping bound vars.

let recursion_limit = self.tcx().recursion_limit();
if !recursion_limit.value_within_limit(self.depth) {
let obligation = Obligation::with_depth(
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8 changes: 4 additions & 4 deletions compiler/rustc_trait_selection/src/traits/query/normalize.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -206,15 +206,15 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for QueryNormalizer<'cx, 'tcx> {

// Wrap this in a closure so we don't accidentally return from the outer function
let res = (|| match *ty.kind() {
ty::Opaque(def_id, substs) => {
// This is really important. While we *can* handle this, this has
// severe performance implications for large opaque types with
// late-bound regions. See `issue-88862` benchmark.
ty::Opaque(def_id, substs) if !substs.has_escaping_bound_vars() => {
// Only normalize `impl Trait` after type-checking, usually in codegen.
match self.param_env.reveal() {
Reveal::UserFacing => ty.super_fold_with(self),

Reveal::All => {
// N.b. there is an assumption here all this code can handle
// escaping bound vars.

let substs = substs.super_fold_with(self);
let recursion_limit = self.tcx().recursion_limit();
if !recursion_limit.value_within_limit(self.anon_depth) {
Expand Down