From a0e12c7b75250a19279ebe034d3b98ac7917c398 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Wed, 7 Feb 2018 12:48:44 -0800
Subject: [PATCH] Use typeMaybeAssignableTo in definitely false check

---
 src/compiler/checker.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 3b1771d2096..948be393e00 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -8144,7 +8144,7 @@ namespace ts {
             // types with type parameters mapped to the wildcard type, the most permissive instantiations
             // possible (the wildcard type is assignable to and from all types). If those are not related,
             // then no instatiations will be and we can just return the false branch type.
-            if (!isTypeAssignableTo(getWildcardInstantiation(checkType), getWildcardInstantiation(extendsType))) {
+            if (!typeMaybeAssignableTo(getWildcardInstantiation(checkType), getWildcardInstantiation(extendsType))) {
                 return instantiateType(baseFalseType, mapper);
             }
             // The check could be true for some instantiation