Bug 1096378 - Disallow duplicated parameter in method definition. r=jorendorff

js/src/frontend/Parser.cpp

@@ -1624,7 +1624,7 @@ Parser<ParseHandler>::functionArguments(FunctionSyntaxKind kind, FunctionType ty
         bool hasDefaults = false;
         Node duplicatedArg = null();
         Node list = null();
-        bool disallowDuplicateArgs = kind == Arrow;
+        bool disallowDuplicateArgs = kind == Arrow || kind == Method;
 
         if (type == Getter) {
             report(ParseError, false, null(), JSMSG_ACCESSOR_WRONG_ARGS, "getter", "no", "s");

js/src/tests/ecma_6/Function/method-has-duplicated.js

@@ -0,0 +1,19 @@
+// Make sure duplicated name is allowed in non-strict.
+function f0(a) {
+}
+
+// SyntaxError should be thrown if method definition has duplicated name.
+assertThrowsInstanceOf(() => eval(`
+({
+  m1(a, a) {
+  }
+});
+`), SyntaxError);
+assertThrowsInstanceOf(() => eval(`
+({
+  m2(a, ...a) {
+  }
+});
+`), SyntaxError);
+
+reportCompare(0, 0, 'ok');