From 2da65c20b0eccd2a92effa6b7a77ed686286a144 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Tue, 24 Jul 2018 17:58:03 -0700
Subject: [PATCH] Address CR feedback

---
 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 3ee66280aeb..c66d85beb93 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -4379,7 +4379,7 @@ namespace ts {
                 case TypeSystemPropertyName.ImmediateBaseConstraint:
                     return !!(<Type>target).immediateBaseConstraint;
             }
-            return Debug.fail("Unhandled TypeSystemPropertyName " + propertyName);
+            return Debug.assertNever(propertyName);
         }
 
         // Pop an entry from the type resolution stack and return its associated result value. The result value will
@@ -7858,6 +7858,7 @@ namespace ts {
             return inferences && getIntersectionType(inferences);
         }
 
+        /** This is a worker function. Use getConstraintOfTypeParameter which guards against circular constraints. */
         function getConstraintFromTypeParameter(typeParameter: TypeParameter): Type | undefined {
             if (!typeParameter.constraint) {
                 if (typeParameter.target) {