From adc7b8ea2d0ff1dafecaa697638825463f4b8891 Mon Sep 17 00:00:00 2001 From: Florian Diebold Date: Tue, 10 Mar 2020 20:56:26 +0100 Subject: Fix completion with a partially unknown type To test whether the receiver type matches for the impl, we unify the given self type (in this case `HashSet<{unknown}>`) with the self type of the impl (`HashSet`), but if the given self type contains Unknowns, they won't be unified with the variables in those places. So we got a receiver type that was different from the expected one, and concluded the impl doesn't match. The fix is slightly hacky; if after the unification, our variables are still there, we make them fall back to Unknown. This does make some sense though, since we don't want to 'leak' the variables. Fixes #3547. --- crates/ra_hir_ty/src/method_resolution.rs | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) (limited to 'crates/ra_hir_ty') 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( let self_ty_with_vars = Canonical { num_vars: vars.len() + self_ty.num_vars, value: self_ty_with_vars }; let substs = super::infer::unify(&self_ty_with_vars, self_ty); - // we only want the substs for the vars we added, not the ones from self_ty - let result = substs.map(|s| s.suffix(vars.len())); - result + // We only want the substs for the vars we added, not the ones from self_ty. + // Also, if any of the vars we added are still in there, we replace them by + // Unknown. I think this can only really happen if self_ty contained + // Unknown, and in that case we want the result to contain Unknown in those + // places again. + substs.map(|s| fallback_bound_vars(s.suffix(vars.len()), self_ty.num_vars)) +} + +/// This replaces any 'free' Bound vars in `s` (i.e. those with indices past +/// num_vars_to_keep) by `Ty::Unknown`. +fn fallback_bound_vars(s: Substs, num_vars_to_keep: usize) -> Substs { + s.fold_binders( + &mut |ty, binders| { + if let Ty::Bound(idx) = &ty { + if *idx >= binders as u32 { + Ty::Unknown + } else { + ty + } + } else { + ty + } + }, + num_vars_to_keep, + ) } fn transform_receiver_ty( -- cgit v1.2.3