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Auto merge of #99814 - aliemjay:patch-2, r=jackh726

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fix universe map in ifcx.instantiate_canonical_*

Previously, `infcx.instantiate_canonical_*` maps the root universe in `canonical` into `ty::UniverseIndex::Root`, I think because it assumes it works with a fresh `infcx` but this is not true for the use cases in mir typeck. Now the root universe is mapped into `infcx.universe()`.

I catched this accidentally while reviewing the code. I'm not sure if this is the right fix or if it is really a bug!
This commit is contained in:
bors 2022-11-30 14:03:36 +00:00
commit 90711a86e5
1 changed files with 6 additions and 3 deletions
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9
compiler/rustc_infer/src/infer/canonical/mod.rs
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@ -41,7 +41,7 @@ impl<'tcx> InferCtxt<'tcx> {
/// inference variables and applies it to the canonical value.
/// Returns both the instantiated result *and* the substitution S.
///
/// This is only meant to be invoked as part of constructing an
/// This can be invoked as part of constructing an
/// inference context at the start of a query (see
/// `InferCtxtBuilder::build_with_canonical`). It basically
/// brings the canonical value "into scope" within your new infcx.
@ -63,8 +63,11 @@ impl<'tcx> InferCtxt<'tcx> {
// in them, so this code has no effect, but it is looking
// forward to the day when we *do* want to carry universes
// through into queries.
let universes: IndexVec<ty::UniverseIndex, _> = std::iter::once(ty::UniverseIndex::ROOT)
.chain((0..canonical.max_universe.as_u32()).map(|_| self.create_next_universe()))
//
// Instantiate the root-universe content into the current universe,
// and create fresh universes for the higher universes.
let universes: IndexVec<ty::UniverseIndex, _> = std::iter::once(self.universe())
.chain((1..=canonical.max_universe.as_u32()).map(|_| self.create_next_universe()))
.collect();
let canonical_inference_vars =