[parser] reject AssignmentElements with non-ASSIGN initializer ops

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 7078 matching lines @@
     "[ (...[a]) ]",
     "[ ...([a]) ]",
     "[ ...([a] = [])",
     "[ ...[ ( [ a ] ) ] ]",
     "[ ([a]) ]",
     "[ (...[a]) ]",
     "[ ([a] = []) ]",
     "[ (++y) ]",
     "[ ...(++y) ]",
 
+    "[ x += x ]",
+    "{ foo: x += x }",
+
     NULL};
   // clang-format on
   static const ParserFlag always_flags[] = {
       kAllowHarmonyDestructuringAssignment, kAllowHarmonyDestructuring,
       kAllowHarmonyDefaultParameters};
   RunParserSyncTest(context_data, data, kError, NULL, 0, always_flags,
                     arraysize(always_flags));
 
   const char* empty_context_data[][2] = {
       {"'use strict';", ""}, {"", ""}, {NULL, NULL}};
 
   // CoverInitializedName ambiguity handling in various contexts
   const char* ambiguity_data[] = {
       "var foo = { x = 10 };",
       "var foo = { q } = { x = 10 };",
       "var foo; foo = { x = 10 };",
       "var foo; foo = { q } = { x = 10 };",
       "var x; ({ x = 10 });",
       "var q, x; ({ q } = { x = 10 });",
       "var x; [{ x = 10 }]",
       "var x; (true ? { x = true } : { x = false })",
       "var q, x; (q, { x = 10 });",
       "var { x = 10 } = { x = 20 };",
       "var { x = 10 } = (o = { x = 20 });",
       "var x; (({ x = 10 } = { x = 20 }) => x)({})",
+
+      // Not ambiguous, but uses same context data
+      "switch([window %= []] = []) { default: }",
+
       NULL,
   };
   RunParserSyncTest(empty_context_data, ambiguity_data, kError, NULL, 0,
                     always_flags, arraysize(always_flags));
 
   // Strict mode errors
   const char* strict_context_data[][2] = {{"'use strict'; (", " = {})"},
                                           {"'use strict'; for (", " of {}) {}"},
                                           {"'use strict'; for (", " in {}) {}"},
                                           {NULL, NULL}};
@@ skipping 689 matching lines @@
 }
 
 
 TEST(MiscSyntaxErrors) {
   const char* context_data[][2] = {
       {"'use strict'", ""}, {"", ""}, {NULL, NULL}};
   const char* error_data[] = {"for (();;) {}", NULL};
 
   RunParserSyncTest(context_data, error_data, kError, NULL, 0, NULL, 0);
 }