From ade89a60327763ac09bc7083d1f9ffc9935682b1 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Mon, 1 Aug 2016 06:41:05 -0700
Subject: [PATCH] Fix issue related to this and #8383

---
 src/compiler/checker.ts | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 691d7451895..155f8a2e676 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7789,6 +7789,10 @@ namespace ts {
             return false;
         }
 
+        function rootContainsMatchingReference(source: Node, target: Node) {
+            return target.kind === SyntaxKind.PropertyAccessExpression && containsMatchingReference(source, (<PropertyAccessExpression>target).expression);
+        }
+
         function isOrContainsMatchingReference(source: Node, target: Node) {
             return isMatchingReference(source, target) || containsMatchingReference(source, target);
         }
@@ -8294,6 +8298,9 @@ namespace ts {
                 if (isMatchingPropertyAccess(expr)) {
                     return narrowTypeByDiscriminant(type, <PropertyAccessExpression>expr, t => getTypeWithFacts(t, assumeTrue ? TypeFacts.Truthy : TypeFacts.Falsy));
                 }
+                if (rootContainsMatchingReference(reference, expr)) {
+                    return declaredType;
+                }
                 return type;
             }
 
@@ -8326,6 +8333,9 @@ namespace ts {
                         if (isMatchingPropertyAccess(right)) {
                             return narrowTypeByDiscriminant(type, <PropertyAccessExpression>right, t => narrowTypeByEquality(t, operator, left, assumeTrue));
                         }
+                        if (rootContainsMatchingReference(reference, left) || rootContainsMatchingReference(reference, right)) {
+                            return declaredType;
+                        }
                         break;
                     case SyntaxKind.InstanceOfKeyword:
                         return narrowTypeByInstanceof(type, expr, assumeTrue);