Address code review

src/compiler/binder.ts

@@ -441,6 +441,9 @@ module ts {
                         bindBlockScopedVariableDeclaration(<Declaration>node);
                     }
                     else if (isParameterDeclaration(<VariableLikeDeclaration>node)) {
+                        // It is safe to walk up parent chain to find whether the node is a destructing parameter declaration
+                        // because its parent chain has already been set up, since parents are set before descending into children.
+                        //
                         // If node is a binding element in parameter declaration, we need to use ParameterExcludes.
                         // Using ParameterExcludes flag allows the compiler to report an error on duplicate identifiers in Parameter Declaration
                         // For example:

src/compiler/checker.ts

@@ -2048,13 +2048,6 @@ module ts {
             return resolutionResults.pop();
         }
 
-        function getRootDeclaration(node: Node): Node {
-            while (node.kind === SyntaxKind.BindingElement) {
-                node = node.parent.parent;
-            }
-            return node;
-        }
-
         function getDeclarationContainer(node: Node): Node {
             node = getRootDeclaration(node);
 

src/compiler/utilities.ts

@@ -1151,10 +1151,15 @@ module ts {
     }
 
     export function isParameterDeclaration(node: VariableLikeDeclaration) {
+        let root = getRootDeclaration(node);
+        return root.kind === SyntaxKind.Parameter;
+    }
+
+    export function getRootDeclaration(node: Node): Node {
         while (node.kind === SyntaxKind.BindingElement) {
-            node = <VariableLikeDeclaration>node.parent.parent;
+            node = node.parent.parent;
         }
-        return node.kind === SyntaxKind.Parameter;
+        return node;
     }
         
     export function nodeStartsNewLexicalEnvironment(n: Node): boolean {