[destructuring] Implement spread binding patterns.

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 6377 matching lines @@
     "{42e-2 : x}",
     "{42e-2 : x = 42}",
     "{'hi' : x}",
     "{'hi' : x = 42}",
     "{var: x}",
     "{var: x = 42}",
     "{[x] : z}",
     "{[1+1] : z}",
     "{[foo()] : z}",
     "{}",
+    "[...rest]",
+    "[a,b,...rest]",
+    "[a,,...rest]",
     NULL};
   // clang-format on
   static const ParserFlag always_flags[] = {kAllowHarmonyObjectLiterals,
                                             kAllowHarmonyComputedPropertyNames,
                                             kAllowHarmonyDestructuring};
   RunParserSyncTest(context_data, data, kSuccess, NULL, 0, always_flags,
                     arraysize(always_flags));
 }
 
 
@@ skipping 52 matching lines @@
         "{+2 : x}",
         "{-2 : x}",
         "var",
         "[var]",
         "{x : {y : var}}",
         "{x : x = a+}",
         "{x : x = (a+)}",
         "{x : x += a}",
         "{m() {} = 0}",
         "{[1+1]}",
+        "[...rest, x]",
+        "[a,b,...rest, x]",
+        "[a,,...rest, x]",
+        "[...rest,]",
+        "[a,b,...rest,]",
+        "[a,,...rest,]",
+        "[...rest,...rest1]",
+        "[a,b,...rest,...rest1]",
+        "[a,,..rest,...rest1]",
         NULL};
     // clang-format on
     RunParserSyncTest(context_data, data, kError, NULL, 0, always_flags,
                       arraysize(always_flags));
   }
 
   {  // Strict mode.
     const char* context_data[][2] = {{"'use strict'; let ", " = {};"},
                                      {"'use strict'; const ", " = {};"},
                                      {NULL, NULL}};
@@ skipping 21 matching lines @@
     const char* data[] = {
       "yield",
       "[yield]",
       "{ x : yield }",
       NULL};
     // clang-format on
     RunParserSyncTest(context_data, data, kError, NULL, 0, always_flags,
                       arraysize(always_flags));
   }
 }