Address the issue that arrow function doesn't have arguments objects

Author: Yui T

src/compiler/checker.ts

@@ -4836,6 +4836,16 @@ module ts {
         function checkIdentifier(node: Identifier): Type {
             var symbol = getResolvedSymbol(node);
 
+			// As noted in ECMAScript 6 language spec, arrow functions never have an arguments objects.
+			// Although in down-level emit of arrow function, we emit it using function expression which means that
+			// arguments objects will be inner bound while emitting arrow function natively in ES6, arguments objects
+			// will be bound to non-arrow function that contain this arrow function. This results in inconsistent bahaviour.
+			// To avoid that we will give an error to users if they use arguments objects in arrow function so that they
+			// can explicitly bound arguments objects
+			if (symbol === argumentsSymbol && getContainingFunction(node).kind === SyntaxKind.ArrowFunction) {
+				error(node, Diagnostics.An_argument_object_has_different_behaviour_across_Javascript_versions_Use_function_expression_or_rest_parameters_instead);
+			}
+
             if (symbol.flags & SymbolFlags.Import) {
                 var symbolLinks = getSymbolLinks(symbol);
                 if (!symbolLinks.referenced) {

src/compiler/diagnosticInformationMap.generated.ts

@@ -452,5 +452,6 @@ module ts {
         You_cannot_rename_this_element: { code: 8000, category: DiagnosticCategory.Error, key: "You cannot rename this element." },
         yield_expressions_are_not_currently_supported: { code: 9000, category: DiagnosticCategory.Error, key: "'yield' expressions are not currently supported.", isEarly: true },
         Generators_are_not_currently_supported: { code: 9001, category: DiagnosticCategory.Error, key: "Generators are not currently supported.", isEarly: true },
+        An_argument_object_has_different_behaviour_across_Javascript_versions_Use_function_expression_or_rest_parameters_instead: { code: 9002, category: DiagnosticCategory.Error, key: "An argument object has different behaviour across Javascript versions. Use function expression or rest parameters instead" },
     };
 }