[strong] Forbid var.

R=rossberg@chromium.org
BUG=

Review URL: https://codereview.chromium.org/927953003

Cr-Commit-Position: refs/heads/master@{#26697}

src/messages.js

@@ -162,6 +162,7 @@ var kMessages = {
   strict_poison_pill:            ["'caller', 'callee', and 'arguments' properties may not be accessed on strict mode functions or the arguments objects for calls to them"],
   strict_caller:                 ["Illegal access to a strict mode caller function."],
   strong_equal:                  ["Please don't use '==' or '!=' in strong mode, use '===' or '!==' instead"],
+  strong_var:                    ["Please don't use 'var' in strong mode, use 'let' or 'const' instead"],
   malformed_arrow_function_parameter_list: ["Malformed arrow function parameter list"],
   generator_poison_pill:         ["'caller' and 'arguments' properties may not be accessed on generator functions."],
   cant_prevent_ext_external_array_elements: ["Cannot prevent extension of an object with external array elements"],

src/parser.cc

@@ -2156,6 +2156,12 @@ Block* Parser::ParseVariableDeclarations(
   bool is_const = false;
   Token::Value init_op = Token::INIT_VAR;
   if (peek() == Token::VAR) {
+    if (is_strong(language_mode())) {
+      Scanner::Location location = scanner()->peek_location();
+      ReportMessageAt(location, "strong_var");
+      *ok = false;
+      return NULL;
+    }
     Consume(Token::VAR);
   } else if (peek() == Token::CONST) {
     Consume(Token::CONST);

src/preparser.cc

@@ -429,6 +429,12 @@ PreParser::Statement PreParser::ParseVariableDeclarations(
   bool require_initializer = false;
   bool is_strict_const = false;
   if (peek() == Token::VAR) {
+    if (is_strong(language_mode())) {
+      Scanner::Location location = scanner()->peek_location();
+      ReportMessageAt(location, "strong_var");
+      *ok = false;
+      return Statement::Default();
+    }
     Consume(Token::VAR);
   } else if (peek() == Token::CONST) {
     // TODO(ES6): The ES6 Draft Rev4 section 12.2.2 reads:

test/cctest/test-parsing.cc

@@ -5453,3 +5453,57 @@ TEST(FunctionLiteralDuplicateParameters) {
                     arraysize(always_flags));
   RunParserSyncTest(sloppy_context_data, data, kSuccess, NULL, 0, NULL, 0);
 }
+
+
+TEST(VarForbiddenInStrongMode) {
+  const char* strong_context_data[][2] =
+      {{"'use strong'; ", ""},
+       {"function f() {'use strong'; ", "}"},
+       {"function f() {'use strong';  while (true) { ", "} }"},
+       {NULL, NULL}};
+
+  const char* strict_context_data[][2] =
+      {{"'use strict'; ", ""},
+       {"function f() {'use strict'; ", "}"},
+       {"function f() {'use strict'; while (true) { ", "} }"},
+       {NULL, NULL}};
+
+  const char* sloppy_context_data[][2] =
+      {{"", ""},
+       {"function f() { ", "}"},
+       {NULL, NULL}};
+
+  const char* var_declarations[] = {
+    "var x = 0;",
+    "for (var i = 0; i < 10; i++) { }",
+    NULL};
+
+  const char* let_declarations[] = {
+    "let x = 0;",
+    "for (let i = 0; i < 10; i++) { }",
+    NULL};
+
+  const char* const_declarations[] = {
+    "const x = 0;",
+    NULL};
+
+  static const ParserFlag always_flags[] = {kAllowStrongMode,
+                                            kAllowHarmonyScoping};
+  RunParserSyncTest(strong_context_data, var_declarations, kError, NULL, 0,
+                    always_flags, arraysize(always_flags));
+  RunParserSyncTest(strong_context_data, let_declarations, kSuccess, NULL, 0,
+                    always_flags, arraysize(always_flags));
+  RunParserSyncTest(strong_context_data, const_declarations, kSuccess, NULL, 0,
+                    always_flags, arraysize(always_flags));
+
+  RunParserSyncTest(strict_context_data, var_declarations, kSuccess, NULL, 0,
+                    always_flags, arraysize(always_flags));
+  RunParserSyncTest(strict_context_data, let_declarations, kSuccess, NULL, 0,
+                    always_flags, arraysize(always_flags));
+
+  RunParserSyncTest(sloppy_context_data, var_declarations, kSuccess, NULL, 0,
+                    always_flags, arraysize(always_flags));
+  // At the moment, let declarations are only available in strict mode.
+  RunParserSyncTest(sloppy_context_data, let_declarations, kError, NULL, 0,
+                    always_flags, arraysize(always_flags));
+}

test/mjsunit/strong/var-let-const.js

@@ -0,0 +1,22 @@
+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --strong-mode
+
+(function NoVar() {
+  assertThrows("'use strong'; var x = 0;", SyntaxError);
+  assertThrows("'use strong'; for(var i = 0; i < 10; ++i) { };", SyntaxError);
+})();
+
+
+(function LetIsOkay() {
+  assertTrue(eval("'use strong'; let x = 0; x === 0;"));
+  assertTrue(eval("'use strong'; for(let i = 0; i < 10; ++i) { } 0 === 0;"));
+})();
+
+
+(function ConstIsOkay() {
+  assertTrue(eval("'use strong'; const x = 0; x === 0;"));
+  assertTrue(eval("'use strong'; for(const i = 0; false;) { } 0 === 0;"));
+})();