From 91fdadba6103b6926ff0c886a6a5da002a80994a Mon Sep 17 00:00:00 2001 From: Ariel Ben-Yehuda Date: Fri, 6 Oct 2017 17:12:24 +0300 Subject: [PATCH] fix logic error in #44269's `prune_cache_value_obligations` We want to retain obligations that *contain* inference variables, not obligations that *don't contain* them, in order to fix #43132. Because of surrounding changes to inference, the ICE doesn't occur in its original case, but I believe it could still be made to occur on master. Maybe I should try to write a new test case? Certainly not right now (I'm mainly trying to get us a beta that we can ship) but maybe before we land this PR on nightly? This seems to cause a 10% performance regression in my imprecise attempt to benchmark item-body checking for #43613, but it's better to be slow and right than fast and wrong. If we want to recover that, I think we can change the constrained-type-parameter code to actually give a list of projections that are important for resolving inference variables and filter everything else out. --- src/librustc/traits/project.rs | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/librustc/traits/project.rs b/src/librustc/traits/project.rs index 54e31aed272..b5449f51769 100644 --- a/src/librustc/traits/project.rs +++ b/src/librustc/traits/project.rs @@ -639,7 +639,7 @@ fn prune_cache_value_obligations<'a, 'gcx, 'tcx>(infcx: &'a InferCtxt<'a, 'gcx, // but we have `T: Foo` and `?1: Bar`). ty::Predicate::Projection(ref data) => - !infcx.any_unresolved_type_vars(&data.ty()), + infcx.any_unresolved_type_vars(&data.ty()), // We are only interested in `T: Foo` predicates, whre // `U` references one of `unresolved_type_vars`. =)