From e6e61d9dff939c1c4ebbae0006efe2a7ac038ff6 Mon Sep 17 00:00:00 2001 From: Markus Westerlind Date: Thu, 2 Jan 2020 12:14:23 +0100 Subject: [PATCH] perf: Don't recurse into types that do not need normalizing A bit speculative at this stage but profiling shows that type folding takes up a substantial amount of time during normalization which may indicate that many types may be folded despite there being nothing to normalize --- src/librustc/traits/project.rs | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/librustc/traits/project.rs b/src/librustc/traits/project.rs index c604bf59cbd79..4b59521a348ef 100644 --- a/src/librustc/traits/project.rs +++ b/src/librustc/traits/project.rs @@ -316,6 +316,9 @@ impl<'a, 'b, 'tcx> TypeFolder<'tcx> for AssocTypeNormalizer<'a, 'b, 'tcx> { } fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { + if !ty.has_projections() { + return ty; + } // We don't want to normalize associated types that occur inside of region // binders, because they may contain bound regions, and we can't cope with that. //