From 9b507b7512290b28bcd710a363f7a98be261a077 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Fri, 11 Dec 2015 15:08:30 -0800
Subject: [PATCH] Specifically test for 'void' to permit implementations to
 return more than what was guaranteed.

---
 src/compiler/checker.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ac8a4ac89a4..a83c1027ad1 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -4987,7 +4987,8 @@ namespace ts {
 
             const sourceReturnType = getReturnTypeOfSignature(erasedSource);
             const targetReturnType = getReturnTypeOfSignature(erasedTarget);
-            if (checkTypeRelatedTo(sourceReturnType, targetReturnType, assignableRelation, /*errorNode*/ undefined)
+            if (targetReturnType === voidType
+                || checkTypeRelatedTo(sourceReturnType, targetReturnType, assignableRelation, /*errorNode*/ undefined)
                 || checkTypeRelatedTo(targetReturnType, sourceReturnType, assignableRelation, /*errorNode*/ undefined)) {
                 const anyReturningSource = cloneSignature(erasedSource);
                 const anyReturningTarget = cloneSignature(erasedTarget);