Fix parsing of arrow function formal parameters

test/cctest/test-parsing.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3492 matching lines @@
       "const y = 1;\n"
       "function bar() {\n"
       "    const z = 1; var baz = 1;\n"
       "    function q() { const k = 42; }\n"
       "}");
   // Optimizing will double-count because the source is parsed twice.
   CHECK_EQ(i::FLAG_always_opt ? 8 : 4, use_counts[v8::Isolate::kLegacyConst]);
 }
 
 
+TEST(ErrorsArrowFormalParameters) {
+  const char* context_data[][2] = {
+    { "()", "=>{}" },
+    { "()", "=>{};" },
+    { "var x = ()", "=>{}" },
+    { "var x = ()", "=>{};" },
+
+    { "a", "=>{}" },
+    { "a", "=>{};" },
+    { "var x = a", "=>{}" },
+    { "var x = a", "=>{};" },
+
+    { "(a)", "=>{}" },
+    { "(a)", "=>{};" },
+    { "var x = (a)", "=>{}" },
+    { "var x = (a)", "=>{};" },
+
+    { "(...a)", "=>{}" },
+    { "(...a)", "=>{};" },
+    { "var x = (...a)", "=>{}" },
+    { "var x = (...a)", "=>{};" },
+
+    { "(a,b)", "=>{}" },
+    { "(a,b)", "=>{};" },
+    { "var x = (a,b)", "=>{}" },
+    { "var x = (a,b)", "=>{};" },
+
+    { "(a,...b)", "=>{}" },
+    { "(a,...b)", "=>{};" },
+    { "var x = (a,...b)", "=>{}" },
+    { "var x = (a,...b)", "=>{};" },
+
+    { nullptr, nullptr }
+  };
+  const char* assignment_expression_suffix_data[] = {
+    "?c:d=>{}",
+    "=c=>{}",
+    "()",
+    "(c)",
+    "[1]",
+    "[c]",
+    ".c",
+    "-c",
+    "+c",
+    "c++",
+    "`c`",
+    "`${c}`",
+    "`template-head${c}`",
+    "`${c}template-tail`",
+    "`template-head${c}template-tail`",
+    "`${c}template-tail`",
+    nullptr
+  };
+
+  static const ParserFlag always_flags[] = { kAllowHarmonyArrowFunctions,
+                                             kAllowHarmonyRestParameters };
+  RunParserSyncTest(context_data, assignment_expression_suffix_data, kError,
+                    NULL, 0, always_flags, arraysize(always_flags));
+}
+
+
 TEST(ErrorsArrowFunctions) {
   // Tests that parser and preparser generate the same kind of errors
   // on invalid arrow function syntax.
   const char* context_data[][2] = {
     {"", ";"},
     {"v = ", ";"},
     {"bar ? (", ") : baz;"},
     {"bar ? baz : (", ");"},
     {"bar[", "];"},
     {"bar, ", ";"},
@@ skipping 3288 matching lines @@
     "for (let x of []) {}",
     NULL
   };
   // clang-format on
 
   static const ParserFlag always_flags[] = {kAllowHarmonySloppy,
                                             kAllowHarmonySloppyLet};
   RunParserSyncTest(context_data, data, kSuccess, NULL, 0, always_flags,
                     arraysize(always_flags));
 }