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-rw-r--r--crates/ra_hir_ty/src/method_resolution.rs28
1 files changed, 25 insertions, 3 deletions
diff --git a/crates/ra_hir_ty/src/method_resolution.rs b/crates/ra_hir_ty/src/method_resolution.rs
index b7e8855fb..7f5e1469e 100644
--- a/crates/ra_hir_ty/src/method_resolution.rs
+++ b/crates/ra_hir_ty/src/method_resolution.rs
@@ -516,9 +516,31 @@ pub(crate) fn inherent_impl_substs(
516 let self_ty_with_vars = 516 let self_ty_with_vars =
517 Canonical { num_vars: vars.len() + self_ty.num_vars, value: self_ty_with_vars }; 517 Canonical { num_vars: vars.len() + self_ty.num_vars, value: self_ty_with_vars };
518 let substs = super::infer::unify(&self_ty_with_vars, self_ty); 518 let substs = super::infer::unify(&self_ty_with_vars, self_ty);
519 // we only want the substs for the vars we added, not the ones from self_ty 519 // We only want the substs for the vars we added, not the ones from self_ty.
520 let result = substs.map(|s| s.suffix(vars.len())); 520 // Also, if any of the vars we added are still in there, we replace them by
521 result 521 // Unknown. I think this can only really happen if self_ty contained
522 // Unknown, and in that case we want the result to contain Unknown in those
523 // places again.
524 substs.map(|s| fallback_bound_vars(s.suffix(vars.len()), self_ty.num_vars))
525}
526
527/// This replaces any 'free' Bound vars in `s` (i.e. those with indices past
528/// num_vars_to_keep) by `Ty::Unknown`.
529fn fallback_bound_vars(s: Substs, num_vars_to_keep: usize) -> Substs {
530 s.fold_binders(
531 &mut |ty, binders| {
532 if let Ty::Bound(idx) = &ty {
533 if *idx >= binders as u32 {
534 Ty::Unknown
535 } else {
536 ty
537 }
538 } else {
539 ty
540 }
541 },
542 num_vars_to_keep,
543 )
522} 544}
523 545
524fn transform_receiver_ty( 546fn transform_receiver_ty(