From 0fa240d232ceadc5c265aa93c2f41c72919446a8 Mon Sep 17 00:00:00 2001
From: Yui T <yuisu@microsoft.com>
Date: Tue, 5 May 2015 15:00:01 -0700
Subject: [PATCH] Check that bindingElement is in parameter declaration and
 pass in correct symbol exclusion flag

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

diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 170f3d3c830..12c8b3e409c 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -440,6 +440,15 @@ module ts {
                     else if (isBlockOrCatchScoped(<Declaration>node)) {
                         bindBlockScopedVariableDeclaration(<Declaration>node);
                     }
+                    else if (isParameterDeclaration(<VariableLikeDeclaration>node)) {
+                        // 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:
+                        //      function foo([a,a]) {} // Duplicate Identifier error
+                        //      function bar(a,a) {}   // Duplicate Identifier error, binding parameter declaration in this case is handled in bindParameter
+                        //                             // which correctly set excluded symbols
+                        bindDeclaration(<Declaration>node, SymbolFlags.FunctionScopedVariable, SymbolFlags.ParameterExcludes, /*isBlockScopeContainer*/ false);
+                    }
                     else {
                         bindDeclaration(<Declaration>node, SymbolFlags.FunctionScopedVariable, SymbolFlags.FunctionScopedVariableExcludes, /*isBlockScopeContainer*/ false);
                     }