From bec090253534b651388e90ec39a7b996fdf48600 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Mon, 7 Oct 2019 10:59:13 -0400
Subject: [PATCH] avoid ICE when extracting closure-kind-ty from a
 canonicalized value

In such a case, the `Infer` is converted to a `Bound`
---
 src/librustc/ty/sty.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index 3f09bf749edc..10935863d531 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -2199,7 +2199,9 @@ impl<'tcx> TyS<'tcx> {
                 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
             },
 
-            Infer(_) => None,
+            // "Bound" types appear in canonical queries when the
+            // closure type is not yet known
+            Bound(..) | Infer(_) => None,
 
             Error => Some(ty::ClosureKind::Fn),