harmony-scoping: Allow 'const' iteration variables in strict mode.

src/parser.cc

 // Copyright 2012 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.
 
 #include "src/v8.h"
 
 #include "src/api.h"
 #include "src/ast.h"
 #include "src/bailout-reason.h"
 #include "src/base/platform/platform.h"
@@ skipping 2138 matching lines @@
   // We mark the block as initializer block because we don't want the
   // rewriter to add a '.result' assignment to such a block (to get compliant
   // behavior for code such as print(eval('var x = 7')), and for cosmetic
   // reasons when pretty-printing. Also, unless an assignment (initialization)
   // is inside an initializer block, it is ignored.
   //
   // Create new block with one expected declaration.
   Block* block = factory()->NewBlock(NULL, 1, true, pos);
   int nvars = 0;  // the number of variables declared
   const AstRawString* name = NULL;
+  bool is_for_iteration_variable;
   do {
     if (fni_ != NULL) fni_->Enter();
 
     // Parse variable name.
     if (nvars > 0) Consume(Token::COMMA);
     name = ParseIdentifier(kDontAllowEvalOrArguments, CHECK_OK);
     if (fni_ != NULL) fni_->PushVariableName(name);
 
     // Declare variable.
     // Note that we *always* must treat the initial value via a separate init
     // assignment for variables and constants because the value must be assigned
     // when the variable is encountered in the source. But the variable/constant
     // is declared (and set to 'undefined') upon entering the function within
     // which the variable or constant is declared. Only function variables have
     // an initial value in the declaration (because they are initialized upon
     // entering the function).
     //
     // If we have a const declaration, in an inner scope, the proxy is always
     // bound to the declared variable (independent of possibly surrounding with
     // statements).
     // For let/const declarations in harmony mode, we can also immediately
     // pre-resolve the proxy because it resides in the same scope as the
     // declaration.
+    is_for_iteration_variable =
+        var_context == kForStatement &&
+        (peek() == Token::IN || PeekContextualKeyword(CStrVector("of")));
+    if (is_for_iteration_variable && mode == CONST) {
+      needs_init = false;
+    }
+
     Interface* interface =
         is_const ? Interface::NewConst() : Interface::NewValue();
     VariableProxy* proxy = NewUnresolved(name, mode, interface);
     Declaration* declaration =
         factory()->NewVariableDeclaration(proxy, mode, scope_, pos);
     Declare(declaration, mode != VAR, CHECK_OK);
     nvars++;
     if (declaration_scope->num_var_or_const() > kMaxNumFunctionLocals) {
       ReportMessage("too_many_variables");
       *ok = false;
@@ skipping 25 matching lines @@
     //   const c; c = x;
     //
     // The "variable" c initialized to x is the same as the declared
     // one - there is no re-lookup (see the last parameter of the
     // Declare() call above).
 
     Scope* initialization_scope = is_const ? declaration_scope : scope_;
     Expression* value = NULL;
     int pos = -1;
     // Harmony consts have non-optional initializers.
-    if (peek() == Token::ASSIGN || mode == CONST) {
+    if (peek() == Token::ASSIGN ||
+        (mode == CONST && !is_for_iteration_variable)) {
       Expect(Token::ASSIGN, CHECK_OK);
       pos = position();
       value = ParseAssignmentExpression(var_context != kForStatement, CHECK_OK);
       // Don't infer if it is "a = function(){...}();"-like expression.
       if (fni_ != NULL &&
           value->AsCall() == NULL &&
           value->AsCallNew() == NULL) {
         fni_->Infer();
       } else {
         fni_->RemoveLastFunction();
@@ skipping 112 matching lines @@
       block->AddStatement(
           factory()->NewExpressionStatement(assignment, RelocInfo::kNoPosition),
           zone());
     }
 
     if (fni_ != NULL) fni_->Leave();
   } while (peek() == Token::COMMA);
 
   // If there was a single non-const declaration, return it in the output
   // parameter for possible use by for/in.
-  if (nvars == 1 && !is_const) {
+  if (nvars == 1 && (!is_const || is_for_iteration_variable)) {
     *out = name;
   }
 
   return block;
 }
 
 
 static bool ContainsLabel(ZoneList<const AstRawString*>* labels,
                           const AstRawString* label) {
   DCHECK(label != NULL);
@@ skipping 716 matching lines @@
 
   // Create an in-between scope for let-bound iteration variables.
   Scope* saved_scope = scope_;
   Scope* for_scope = NewScope(scope_, BLOCK_SCOPE);
   scope_ = for_scope;
 
   Expect(Token::FOR, CHECK_OK);
   Expect(Token::LPAREN, CHECK_OK);
   for_scope->set_start_position(scanner()->location().beg_pos);
   if (peek() != Token::SEMICOLON) {
-    if (peek() == Token::VAR || peek() == Token::CONST) {
+    if (peek() == Token::VAR ||
+        (peek() == Token::CONST && strict_mode() == SLOPPY)) {
       bool is_const = peek() == Token::CONST;
       const AstRawString* name = NULL;
       VariableDeclarationProperties decl_props = kHasNoInitializers;
       Block* variable_statement =
           ParseVariableDeclarations(kForStatement, &decl_props, NULL, &name,
                                     CHECK_OK);
       bool accept_OF = decl_props == kHasNoInitializers;
       ForEachStatement::VisitMode mode;
 
       if (name != NULL && CheckInOrOf(accept_OF, &mode)) {
@@ skipping 16 matching lines @@
         result->AddStatement(loop, zone());
         scope_ = saved_scope;
         for_scope->set_end_position(scanner()->location().end_pos);
         for_scope = for_scope->FinalizeBlockScope();
         DCHECK(for_scope == NULL);
         // Parsed for-in loop w/ variable/const declaration.
         return result;
       } else {
         init = variable_statement;
       }
-    } else if (peek() == Token::LET && strict_mode() == STRICT) {
-      DCHECK(allow_harmony_scoping());
+    } else if ((peek() == Token::LET || peek() == Token::CONST) &&
+               strict_mode() == STRICT) {
+      bool is_const = peek() == Token::CONST;
       const AstRawString* name = NULL;
       VariableDeclarationProperties decl_props = kHasNoInitializers;
       Block* variable_statement =
           ParseVariableDeclarations(kForStatement, &decl_props, &let_bindings,
                                     &name, CHECK_OK);
       bool accept_IN = name != NULL && decl_props != kHasInitializers;
       bool accept_OF = decl_props == kHasNoInitializers;
       ForEachStatement::VisitMode mode;
 
       if (accept_IN && CheckInOrOf(accept_OF, &mode)) {
         // Rewrite a for-in statement of the form
         //
-        //   for (let x in e) b
+        //   for (let/const x in e) b
         //
         // into
         //
         //   <let x' be a temporary variable>
         //   for (x' in e) {
-        //     let x;
+        //     let/const x;
         //     x = x';
         //     b;
         //   }
 
         // TODO(keuchel): Move the temporary variable to the block scope, after
         // implementing stack allocated block scoped variables.
         Variable* temp = scope_->DeclarationScope()->NewTemporary(
             ast_value_factory()->dot_for_string());
         VariableProxy* temp_proxy = factory()->NewVariableProxy(temp);
         ForEachStatement* loop =
             factory()->NewForEachStatement(mode, labels, pos);
         Target target(&this->target_stack_, loop);
 
         // The expression does not see the loop variable.
         scope_ = saved_scope;
         Expression* enumerable = ParseExpression(true, CHECK_OK);
         scope_ = for_scope;
         Expect(Token::RPAREN, CHECK_OK);
 
-        VariableProxy* each =
-            scope_->NewUnresolved(factory(), name, Interface::NewValue());
+        VariableProxy* each = scope_->NewUnresolved(factory(), name);
         Statement* body = ParseStatement(NULL, CHECK_OK);
         Block* body_block =
             factory()->NewBlock(NULL, 3, false, RelocInfo::kNoPosition);
+        Token::Value init_op = is_const ? Token::INIT_CONST : Token::ASSIGN;
         Assignment* assignment = factory()->NewAssignment(
-            Token::ASSIGN, each, temp_proxy, RelocInfo::kNoPosition);
+            init_op, each, temp_proxy, RelocInfo::kNoPosition);
         Statement* assignment_statement = factory()->NewExpressionStatement(
             assignment, RelocInfo::kNoPosition);
         body_block->AddStatement(variable_statement, zone());
         body_block->AddStatement(assignment_statement, zone());
         body_block->AddStatement(body, zone());
         InitializeForEachStatement(loop, temp_proxy, enumerable, body_block);
         scope_ = saved_scope;
         for_scope->set_end_position(scanner()->location().end_pos);
         for_scope = for_scope->FinalizeBlockScope();
         body_block->set_scope(for_scope);
@@ skipping 1759 matching lines @@
 
   // We cannot internalize on a background thread; a foreground task will take
   // care of calling Parser::Internalize just before compilation.
 
   if (compile_options() == ScriptCompiler::kProduceParserCache) {
     if (result != NULL) *info_->cached_data() = recorder.GetScriptData();
     log_ = NULL;
   }
 }
 } }  // namespace v8::internal