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+// |reftest| error:SyntaxError
+// Copyright 2019 Mike Pennisi. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-arrow-function-definitions
+description: Formal parameters may not contain duplicates
+info: |
+  # 14.2 Arrow Function Definitions
+
+  When the production
+
+    ArrowParameters:CoverParenthesizedExpressionAndArrowParameterList
+
+  is recognized the following grammar is used to refine the interpretation
+  of CoverParenthesizedExpressionAndArrowParameterList:
+
+    ArrowFormalParameters[Yield, Await]:
+      (UniqueFormalParameters[?Yield, ?Await])
+
+  # 14.1.2 Static Semantics: Early Errors
+
+  UniqueFormalParameters:FormalParameters
+
+  - It is a Syntax Error if BoundNames of FormalParameters contains any
+    duplicate elements.
+negative:
+  phase: parse
+  type: SyntaxError
+---*/
+
+$DONOTEVALUATE();
+
+0, (a, a) => { };