diff options
| -rw-r--r-- | src/librustc/infer/region_inference/mod.rs | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/src/librustc/infer/region_inference/mod.rs b/src/librustc/infer/region_inference/mod.rs index 0bc388a0089..4c8a72512f1 100644 --- a/src/librustc/infer/region_inference/mod.rs +++ b/src/librustc/infer/region_inference/mod.rs @@ -633,6 +633,9 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> { debug!("RegionVarBindings: add_constraint({:?})", constraint); + // never overwrite an existing (constraint, origin) - only insert one if it isn't + // present in the map yet. This prevents origins from outside the snapshot being + // replaced with "less informative" origins e.g. during calls to `can_eq` self.constraints.borrow_mut().entry(constraint).or_insert_with(|| { if self.in_snapshot() { self.undo_log.borrow_mut().push(AddConstraint(constraint)); |