Parse harmony let declarations.

src/parser.cc

 // Copyright 2011 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 793 matching lines @@
   Handle<FixedArray> elements = factory->NewFixedArray(args.length());
   for (int i = 0; i < args.length(); i++) {
     elements->set(i, *args[i]);
   }
   Handle<JSArray> array = factory->NewJSArrayWithElements(elements);
   Handle<Object> result = factory->NewSyntaxError(type, array);
   isolate()->Throw(*result, &location);
 }
 
 void Parser::SetHarmonyBlockScoping(bool block_scoping) {
+  scanner().SetHarmonyBlockScoping(block_scoping);
   harmony_block_scoping_ = block_scoping;
 }
 
 // Base class containing common code for the different finder classes used by
 // the parser.
 class ParserFinder {
  protected:
   ParserFinder() {}
   static Assignment* AsAssignment(Statement* stat) {
     if (stat == NULL) return NULL;
@@ skipping 262 matching lines @@
   }
 
   Isolate* isolate_;
   bool only_simple_this_property_assignments_;
   ZoneStringList* names_;
   ZoneList<int>* assigned_arguments_;
   ZoneObjectList* assigned_constants_;
 };
 
 
+Statement* Parser::ParseSourceElement(ZoneStringList* labels,
+                                      bool* ok) {
+  if (peek() == Token::FUNCTION) {
+    // FunctionDeclaration is only allowed in the context of SourceElements
+    // (Ecma 262 5th Edition, clause 14):
+    // SourceElement:
+    //    Statement
+    //    FunctionDeclaration
+    // Common language extension is to allow function declaration in place
+    // of any statement. This language extension is disabled in strict mode.
+    return ParseFunctionDeclaration(ok);
+  } else if (peek() == Token::LET) {
+    return ParseVariableStatement(kSourceElement, ok);
+  } else {
+    return ParseStatement(labels, ok);
+  }
+}
+
+
 void* Parser::ParseSourceElements(ZoneList<Statement*>* processor,
                                   int end_token,
                                   bool* ok) {
   // SourceElements ::
   //   (Statement)* <end_token>
 
   // Allocate a target stack to use for this set of source
   // elements. This way, all scripts and functions get their own
   // target stack thus avoiding illegal breaks and continues across
   // functions.
   TargetScope scope(&this->target_stack_);
 
   ASSERT(processor != NULL);
   InitializationBlockFinder block_finder(top_scope_, target_stack_);
   ThisNamedPropertyAssigmentFinder this_property_assignment_finder(isolate());
   bool directive_prologue = true;     // Parsing directive prologue.
 
   while (peek() != end_token) {
     if (directive_prologue && peek() != Token::STRING) {
       directive_prologue = false;
     }
 
     Scanner::Location token_loc = scanner().peek_location();
-
-    Statement* stat;
-    if (peek() == Token::FUNCTION) {
-      // FunctionDeclaration is only allowed in the context of SourceElements
-      // (Ecma 262 5th Edition, clause 14):
-      // SourceElement:
-      //    Statement
-      //    FunctionDeclaration
-      // Common language extension is to allow function declaration in place
-      // of any statement. This language extension is disabled in strict mode.
-      stat = ParseFunctionDeclaration(CHECK_OK);
-    } else {
-      stat = ParseStatement(NULL, CHECK_OK);
-    }
-
+    Statement* stat = ParseSourceElement(NULL, CHECK_OK);
     if (stat == NULL || stat->IsEmpty()) {
       directive_prologue = false;   // End of directive prologue.
       continue;
     }
 
     if (directive_prologue) {
       // A shot at a directive.
       ExpressionStatement *e_stat;
       Literal *literal;
       // Still processing directive prologue?
@@ skipping 67 matching lines @@
 
   // Keep the source position of the statement
   int statement_pos = scanner().peek_location().beg_pos;
   Statement* stmt = NULL;
   switch (peek()) {
     case Token::LBRACE:
       return ParseBlock(labels, ok);
 
     case Token::CONST:  // fall through
     case Token::VAR:
-      stmt = ParseVariableStatement(ok);
+      stmt = ParseVariableStatement(kStatement, ok);
       break;
 
     case Token::SEMICOLON:
       Next();
       return EmptyStatement();
 
     case Token::IF:
       stmt = ParseIfStatement(labels, ok);
       break;
 
@@ skipping 74 matching lines @@
   return stmt;
 }
 
 
 VariableProxy* Parser::Declare(Handle<String> name,
                                Variable::Mode mode,
                                FunctionLiteral* fun,
                                bool resolve,
                                bool* ok) {
   Variable* var = NULL;
-  // If we are inside a function, a declaration of a variable
-  // is a truly local variable, and the scope of the variable
-  // is always the function scope.
+  // If we are inside a function, a declaration of a var/const variable is a
+  // truly local variable, and the scope of the variable is always the function
+  // scope.
 
   // If a function scope exists, then we can statically declare this
   // variable and also set its mode. In any case, a Declaration node
   // will be added to the scope so that the declaration can be added
   // to the corresponding activation frame at runtime if necessary.
   // For instance declarations inside an eval scope need to be added
   // to the calling function context.
   // Similarly, strict mode eval scope does not leak variable declarations to
   // the caller's scope so we declare all locals, too.
-  Scope* declaration_scope = top_scope_->DeclarationScope();
+
+  Scope* declaration_scope = mode == Variable::LET ? top_scope_
+      : top_scope_->DeclarationScope();
   if (declaration_scope->is_function_scope() ||
-      declaration_scope->is_strict_mode_eval_scope()) {
+      declaration_scope->is_strict_mode_eval_scope() ||
+      declaration_scope->is_block_scope()) {
     // Declare the variable in the function scope.
     var = declaration_scope->LocalLookup(name);
     if (var == NULL) {
       // Declare the name.
       var = declaration_scope->DeclareLocal(name, mode);
     } else {
-      // The name was declared before; check for conflicting
-      // re-declarations. If the previous declaration was a const or the
-      // current declaration is a const then we have a conflict. There is
-      // similar code in runtime.cc in the Declare functions.
-      if ((mode == Variable::CONST) || (var->mode() == Variable::CONST)) {
-        // We only have vars and consts in declarations.
+      // The name was declared before; check for conflicting re-declarations.
+      // We have a conflict if either of the declarations is not a var. There
+      // is similar code in runtime.cc in the Declare functions.
+      if ((mode != Variable::VAR) || (var->mode() != Variable::VAR)) {
+        // We only have vars, consts and lets in declarations.
         ASSERT(var->mode() == Variable::VAR ||
-               var->mode() == Variable::CONST);
-        const char* type = (var->mode() == Variable::VAR) ? "var" : "const";
+               var->mode() == Variable::CONST ||
+               var->mode() == Variable::LET);
+        const char* type = (var->mode() == Variable::VAR) ? "var" :
+                           (var->mode() == Variable::CONST) ? "const" : "let";
         Handle<String> type_string =
             isolate()->factory()->NewStringFromUtf8(CStrVector(type), TENURED);
         Expression* expression =
             NewThrowTypeError(isolate()->factory()->redeclaration_symbol(),
                               type_string, name);
         declaration_scope->SetIllegalRedeclaration(expression);
       }
     }
   }
 
@@ skipping 122 matching lines @@
   Handle<String> name = ParseIdentifierOrStrictReservedWord(
       &is_strict_reserved, CHECK_OK);
   FunctionLiteral* fun = ParseFunctionLiteral(name,
                                               is_strict_reserved,
                                               function_token_position,
                                               FunctionLiteral::DECLARATION,
                                               CHECK_OK);
   // Even if we're not at the top-level of the global or a function
   // scope, we treat is as such and introduce the function with it's
   // initial value upon entering the corresponding scope.
-  Declare(name, Variable::VAR, fun, true, CHECK_OK);
+  Variable::Mode mode = harmony_block_scoping_ ? Variable::LET : Variable::VAR;
+  Declare(name, mode, fun, true, CHECK_OK);
   return EmptyStatement();
 }
 
 
 Block* Parser::ParseBlock(ZoneStringList* labels, bool* ok) {
   if (harmony_block_scoping_) return ParseScopedBlock(labels, ok);
 
   // Block ::
   //   '{' Statement* '}'
 
@@ skipping 34 matching lines @@
 
   // Parse the statements and collect escaping labels.
   TargetCollector collector;
   Target target(&this->target_stack_, &collector);
   Expect(Token::LBRACE, CHECK_OK);
   {
     Target target_body(&this->target_stack_, body);
     InitializationBlockFinder block_finder(top_scope_, target_stack_);
 
     while (peek() != Token::RBRACE) {
-      Statement* stat = ParseStatement(NULL, CHECK_OK);
+      Statement* stat = ParseSourceElement(NULL, CHECK_OK);
       if (stat && !stat->IsEmpty()) {
         body->AddStatement(stat);
         block_finder.Update(stat);
       }
     }
   }
   Expect(Token::RBRACE, CHECK_OK);
 
   // Create exit block.
   Block* exit = new(zone()) Block(isolate(), NULL, 1, false);
   exit->AddStatement(new(zone()) ExitContextStatement());
 
   // Create a try-finally statement.
   TryFinallyStatement* try_finally =
       new(zone()) TryFinallyStatement(body, exit);
   try_finally->set_escaping_targets(collector.targets());
   top_scope_ = saved_scope;
 
   // Create a result block.
   Block* result = new(zone()) Block(isolate(), NULL, 1, false);
   result->AddStatement(try_finally);
   return result;
 }
 
 
-Block* Parser::ParseVariableStatement(bool* ok) {
+Block* Parser::ParseVariableStatement(VariableDeclarationContext var_context,
+                                      bool* ok) {
   // VariableStatement ::
   //   VariableDeclarations ';'
 
   Handle<String> ignore;
-  Block* result = ParseVariableDeclarations(true, &ignore, CHECK_OK);
+  Block* result = ParseVariableDeclarations(var_context,
+                                            &ignore,
+                                            CHECK_OK);
   ExpectSemicolon(CHECK_OK);
   return result;
 }
 
 
 bool Parser::IsEvalOrArguments(Handle<String> string) {
   return string.is_identical_to(isolate()->factory()->eval_symbol()) ||
       string.is_identical_to(isolate()->factory()->arguments_symbol());
 }
 
 
 // If the variable declaration declares exactly one non-const
 // variable, then *var is set to that variable. In all other cases,
 // *var is untouched; in particular, it is the caller's responsibility
 // to initialize it properly. This mechanism is used for the parsing
 // of 'for-in' loops.
-Block* Parser::ParseVariableDeclarations(bool accept_IN,
+Block* Parser::ParseVariableDeclarations(VariableDeclarationContext var_context,
                                          Handle<String>* out,
                                          bool* ok) {
   // VariableDeclarations ::
   //   ('var' | 'const') (Identifier ('=' AssignmentExpression)?)+[',']
 
   Variable::Mode mode = Variable::VAR;
   bool is_const = false;
-  Scope* declaration_scope = top_scope_->DeclarationScope();
   if (peek() == Token::VAR) {
     Consume(Token::VAR);
   } else if (peek() == Token::CONST) {
     Consume(Token::CONST);
-    if (declaration_scope->is_strict_mode()) {
+    if (top_scope_->is_strict_mode()) {
       ReportMessage("strict_const", Vector<const char*>::empty());
       *ok = false;
       return NULL;
     }
     mode = Variable::CONST;
     is_const = true;
+  } else if (peek() == Token::LET) {
+    Consume(Token::LET);
+    if (var_context != kSourceElement &&
+        var_context != kForStatement) {
+      ASSERT(var_context == kStatement);
+      ReportMessage("unprotected_let", Vector<const char*>::empty());
+      *ok = false;
+      return NULL;
+    }
+    mode = Variable::LET;
   } else {
     UNREACHABLE();  // by current callers
   }
 
-  // The scope of a variable/const declared anywhere inside a function
+  Scope* declaration_scope = mode == Variable::LET
+      ? top_scope_ : top_scope_->DeclarationScope();
+  // The scope of a var/const declared variable anywhere inside a function
   // is the entire function (ECMA-262, 3rd, 10.1.3, and 12.2). Thus we can
-  // transform a source-level variable/const declaration into a (Function)
+  // transform a source-level var/const declaration into a (Function)
   // Scope declaration, and rewrite the source-level initialization into an
   // assignment statement. We use a block to collect multiple assignments.
   //
   // 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.
@@ skipping 63 matching lines @@
     // 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 : top_scope_;
     Expression* value = NULL;
     int position = -1;
     if (peek() == Token::ASSIGN) {
       Expect(Token::ASSIGN, CHECK_OK);
       position = scanner().location().beg_pos;
-      value = ParseAssignmentExpression(accept_IN, CHECK_OK);
+      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();
       }
     }
 
     // Make sure that 'const c' actually initializes 'c' to undefined
     // even though it seems like a stupid thing to do.
@@ skipping 579 matching lines @@
   //   'for' '(' Expression? ';' Expression? ';' Expression? ')' Statement
 
   Statement* init = NULL;
 
   Expect(Token::FOR, CHECK_OK);
   Expect(Token::LPAREN, CHECK_OK);
   if (peek() != Token::SEMICOLON) {
     if (peek() == Token::VAR || peek() == Token::CONST) {
       Handle<String> name;
       Block* variable_statement =
-          ParseVariableDeclarations(false, &name, CHECK_OK);
+          ParseVariableDeclarations(kForStatement, &name, CHECK_OK);
 
       if (peek() == Token::IN && !name.is_null()) {
         VariableProxy* each = top_scope_->NewUnresolved(name, inside_with());
         ForInStatement* loop = new(zone()) ForInStatement(isolate(), labels);
         Target target(&this->target_stack_, loop);
 
         Expect(Token::IN, CHECK_OK);
         Expression* enumerable = ParseExpression(true, CHECK_OK);
         Expect(Token::RPAREN, CHECK_OK);
 
@@ skipping 1338 matching lines @@
   // handle as the function name.  Remember if we were passed a non-empty
   // handle to decide whether to invoke function name inference.
   bool should_infer_name = function_name.is_null();
 
   // We want a non-null handle as the function name.
   if (should_infer_name) {
     function_name = isolate()->factory()->empty_symbol();
   }
 
   int num_parameters = 0;
-  // Function declarations are hoisted.
-  Scope* scope = (type == FunctionLiteral::DECLARATION)
+  // Function declarations are function scoped in normal mode, so they are
+  // hoisted. In harmony block scoping mode they are block scoped, so they
+  // are not hoisted.
+  Scope* scope = (type == FunctionLiteral::DECLARATION &&
+                  !harmony_block_scoping_)
       ? NewScope(top_scope_->DeclarationScope(), Scope::FUNCTION_SCOPE, false)
       : NewScope(top_scope_, Scope::FUNCTION_SCOPE, inside_with());
   ZoneList<Statement*>* body = new(zone()) ZoneList<Statement*>(8);
   int materialized_literal_count;
   int expected_property_count;
   int start_pos;
   int end_pos;
   bool only_simple_this_property_assignments;
   Handle<FixedArray> this_property_assignments;
   bool has_duplicate_parameters = false;
@@ skipping 281 matching lines @@
 Literal* Parser::GetLiteralTheHole() {
   return NewLiteral(isolate()->factory()->the_hole_value());
 }
 
 
 Literal* Parser::GetLiteralNumber(double value) {
   return NewNumberLiteral(value);
 }
 
 
-// Parses and identifier that is valid for the current scope, in particular it
+// Parses an identifier that is valid for the current scope, in particular it
 // fails on strict mode future reserved keywords in a strict scope.
 Handle<String> Parser::ParseIdentifier(bool* ok) {
   if (top_scope_->is_strict_mode()) {
     Expect(Token::IDENTIFIER, ok);
   } else if (!Check(Token::IDENTIFIER)) {
     Expect(Token::FUTURE_STRICT_RESERVED_WORD, ok);
   }
   if (!*ok) return Handle<String>();
   return GetSymbol(ok);
 }
@@ skipping 1060 matching lines @@
     data++;
   }
   *source = data;
   return result;
 }
 
 
 // Create a Scanner for the preparser to use as input, and preparse the source.
 static ScriptDataImpl* DoPreParse(UC16CharacterStream* source,
                                   bool allow_lazy,
-                                  ParserRecorder* recorder) {
+                                  ParserRecorder* recorder,
+                                  bool harmony_block_scoping) {
   Isolate* isolate = Isolate::Current();
   JavaScriptScanner scanner(isolate->unicode_cache());
   scanner.Initialize(source);
+  scanner.SetHarmonyBlockScoping(harmony_block_scoping);
   intptr_t stack_limit = isolate->stack_guard()->real_climit();
   if (!preparser::PreParser::PreParseProgram(&scanner,
                                              recorder,
                                              allow_lazy,
                                              stack_limit)) {
     isolate->StackOverflow();
     return NULL;
   }
 
   // Extract the accumulated data from the recorder as a single
   // contiguous vector that we are responsible for disposing.
   Vector<unsigned> store = recorder->ExtractData();
   return new ScriptDataImpl(store);
 }
 
 
 // Preparse, but only collect data that is immediately useful,
 // even if the preparser data is only used once.
 ScriptDataImpl* ParserApi::PartialPreParse(UC16CharacterStream* source,
-                                           v8::Extension* extension) {
+                                           v8::Extension* extension,
+                                           bool harmony_block_scoping) {
   bool allow_lazy = FLAG_lazy && (extension == NULL);
   if (!allow_lazy) {
     // Partial preparsing is only about lazily compiled functions.
     // If we don't allow lazy compilation, the log data will be empty.
     return NULL;
   }
   PartialParserRecorder recorder;
-  return DoPreParse(source, allow_lazy, &recorder);
+  return DoPreParse(source, allow_lazy, &recorder, harmony_block_scoping);
 }
 
 
 ScriptDataImpl* ParserApi::PreParse(UC16CharacterStream* source,
-                                    v8::Extension* extension) {
+                                    v8::Extension* extension,
+                                    bool harmony_block_scoping) {
   Handle<Script> no_script;
   bool allow_lazy = FLAG_lazy && (extension == NULL);
   CompleteParserRecorder recorder;
-  return DoPreParse(source, allow_lazy, &recorder);
+  return DoPreParse(source, allow_lazy, &recorder, harmony_block_scoping);
 }
 
 
 bool RegExpParser::ParseRegExp(FlatStringReader* input,
                                bool multiline,
                                RegExpCompileData* result) {
   ASSERT(result != NULL);
   RegExpParser parser(input, &result->error, multiline);
   RegExpTree* tree = parser.ParsePattern();
   if (parser.failed()) {
     ASSERT(tree == NULL);
     ASSERT(!result->error.is_null());
   } else {
     ASSERT(tree != NULL);
     ASSERT(result->error.is_null());
     result->tree = tree;
     int capture_count = parser.captures_started();
     result->simple = tree->IsAtom() && parser.simple() && capture_count == 0;
     result->contains_anchor = parser.contains_anchor();
     result->capture_count = capture_count;
   }
   return !parser.failed();
 }
 
 
 bool ParserApi::Parse(CompilationInfo* info) {
   ASSERT(info->function() == NULL);
   FunctionLiteral* result = NULL;
   Handle<Script> script = info->script();
+  bool harmony_block_scoping = !info->is_native() &&
+                               FLAG_harmony_block_scoping;
   if (info->is_lazy()) {
     Parser parser(script, true, NULL, NULL);
-    parser.SetHarmonyBlockScoping(!info->is_native() &&
-                                  FLAG_harmony_block_scoping);
+    parser.SetHarmonyBlockScoping(harmony_block_scoping);
     result = parser.ParseLazy(info);
   } else {
     // Whether we allow %identifier(..) syntax.
     bool allow_natives_syntax =
         info->allows_natives_syntax() || FLAG_allow_natives_syntax;
     ScriptDataImpl* pre_data = info->pre_parse_data();
-    Parser parser(script, allow_natives_syntax, info->extension(), pre_data);
-    parser.SetHarmonyBlockScoping(!info->is_native() &&
-                                  FLAG_harmony_block_scoping);
+    Parser parser(script,
+                  allow_natives_syntax,
+                  info->extension(),
+                  pre_data);
+    parser.SetHarmonyBlockScoping(harmony_block_scoping);
     if (pre_data != NULL && pre_data->has_error()) {
       Scanner::Location loc = pre_data->MessageLocation();
       const char* message = pre_data->BuildMessage();
       Vector<const char*> args = pre_data->BuildArgs();
       parser.ReportMessageAt(loc, message, args);
       DeleteArray(message);
       for (int i = 0; i < args.length(); i++) {
         DeleteArray(args[i]);
       }
       DeleteArray(args.start());
       ASSERT(info->isolate()->has_pending_exception());
     } else {
       Handle<String> source = Handle<String>(String::cast(script->source()));
       result = parser.ParseProgram(source,
                                    info->is_global(),
                                    info->StrictMode());
     }
   }
   info->SetFunction(result);
   return (result != NULL);
 }
 
 } }  // namespace v8::internal