Rollup merge of #115559 - lcnr:implied-bounds-unconstrained, r=aliemjay

implied bounds: do not ICE on unconstrained region vars fixes #112832 see tests/ui/implied-bounds/implied-bounds-unconstrained-2.rs for a minimal example showing why this is necessary. r? types cc ``@compiler-errors`` ``@aliemjay`` https://rust-lang.zulipchat.com/#narrow/stream/144729-t-types/topic/assoc.20type.20bound.20in.20super.20trait
rust-lang · Sep 5, 2023 · 8c04907 · 8c04907
2 parents c7d5c12 98fa0c9
commit 8c04907
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Showing 3 changed files with 53 additions and 9 deletions.
diff --git a/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
@@ -57,16 57,12 @@ impl<'a, 'tcx: 'a> InferCtxtExt<'a, 'tcx> for InferCtxt<'tcx> {
  let ty = OpportunisticRegionResolver::new(self).fold_ty(ty);
 
  // We do not expect existential variables in implied bounds.
- // We may however encounter unconstrained lifetime variables in invalid
- // code. See #110161 for context.
  // We may however encounter unconstrained lifetime variables
  // in very rare cases.
  //
  // See `ui/implied-bounds/implied-bounds-unconstrained-2.rs` for
  // an example.
  assert!(!ty.has_non_region_infer());
- if ty.has_infer() {
- self.tcx.sess.delay_span_bug(
- self.tcx.def_span(body_id),
- "skipped implied_outlives_bounds due to unconstrained lifetimes",
- );
- return vec![];
- }
 
  let mut canonical_var_values = OriginalQueryValues::default();
  let canonical_ty =

diff --git a/tests/ui/implied-bounds/implied-bounds-unconstrained-1.rs b/tests/ui/implied-bounds/implied-bounds-unconstrained-1.rs
@@ -0,0 1,28 @@
 // check-pass
 
 // Regression test for #112832.
 pub trait QueryDb {
  type Db;
 }
 
 pub struct QueryTable<Q, DB> {
  db: DB,
  storage: Q,
 }
 
 // We normalize `<Q as QueryDb>::Db` to `<Q as AsyncQueryFunction<'d>>::SendDb`
 // using the where-bound. 'd is an unconstrained region variable which previously
 // triggered an assert.
 impl<Q> QueryTable<Q, <Q as QueryDb>::Db> where Q: for<'d> AsyncQueryFunction<'d> {}
 
 pub trait AsyncQueryFunction<'d>: QueryDb<Db = <Self as AsyncQueryFunction<'d>>::SendDb> {
  type SendDb: 'd;
 }
 
 pub trait QueryStorageOpsAsync<Q>
 where
  Q: for<'d> AsyncQueryFunction<'d>,
 {
 }
 
 fn main() {}
diff --git a/tests/ui/implied-bounds/implied-bounds-unconstrained-2.rs b/tests/ui/implied-bounds/implied-bounds-unconstrained-2.rs
@@ -0,0 1,20 @@
 // check-pass
 
 // Another minimized regression test for #112832.
 trait Trait {
  type Assoc;
 }
 
 trait Sub<'a>: Trait<Assoc = <Self as Sub<'a>>::SubAssoc> {
  type SubAssoc;
 }
 
 // By using the where-clause we normalize `<T as Trait>::Assoc` to
 // `<T as Sub<'a>>::SubAssoc` where `'a` is an unconstrained region
 // variable.
 fn foo<T>(x: <T as Trait>::Assoc)
 where
  for<'a> T: Sub<'a>,
 {}
 
 fn main() {}