From a292da593bb4d059c84b0510b8b234dbe448119c Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Wed, 23 Sep 2015 14:45:09 -0700
Subject: [PATCH] Check if binding element already has been assigned a
 contextual type

---
 src/compiler/checker.ts | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 2aee597092d..b0a695e1e7d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2293,10 +2293,17 @@ namespace ts {
             return type && (type.flags & TypeFlags.Any) !== 0;
         }
 
+        // Return the type of a binding element parent. We check SymbolLinks first to see if a type has been
+        // assigned by contextual typing.
+        function getTypeForBindingElementParent(node: VariableLikeDeclaration) {
+            let symbol = getSymbolOfNode(node);
+            return symbol && getSymbolLinks(symbol).type || getTypeForVariableLikeDeclaration(node);
+        }
+
         // Return the inferred type for a binding element
         function getTypeForBindingElement(declaration: BindingElement): Type {
             let pattern = <BindingPattern>declaration.parent;
-            let parentType = getTypeForVariableLikeDeclaration(<VariableLikeDeclaration>pattern.parent);
+            let parentType = getTypeForBindingElementParent(<VariableLikeDeclaration>pattern.parent);
             // If parent has the unknown (error) type, then so does this binding element
             if (parentType === unknownType) {
                 return unknownType;