From b9f805f2f44a4ae94f8215d63df52abd827a9c2f Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Sat, 13 Apr 2019 08:15:28 -1000
Subject: [PATCH] Remove incorrect optimization in
 getUnionConstraintOfIntersection

---
 src/compiler/checker.ts | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 7becc4a2f78..72e85b3f8a8 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7598,11 +7598,6 @@ namespace ts {
                         constraint = getConstraintOfType(constraint);
                     }
                     if (constraint) {
-                        // A constraint that isn't a union type implies that the final type would be a non-union
-                        // type as well. Since non-union constraints are of no interest, we can exit here.
-                        if (!(constraint.flags & TypeFlags.Union)) {
-                            return undefined;
-                        }
                         constraints = append(constraints, constraint);
                     }
                 }