Remove redundant/unnecessary variables and checks in ParseForStatement

Review URL: https://codereview.chromium.org/1663773003

Cr-Commit-Position: refs/heads/master@{#33748}

src/ast/ast.h

@@ -831,6 +831,10 @@ class ForEachStatement : public IterationStatement {
                                  FeedbackVectorSlotCache* cache) override;
   FeedbackVectorSlot EachFeedbackSlot() const { return each_slot_; }
 
+  static const char* VisitModeString(VisitMode mode) {
+    return mode == ITERATE ? "for-of" : "for-in";
+  }
+
  protected:
   ForEachStatement(Zone* zone, ZoneList<const AstRawString*>* labels, int pos)
       : IterationStatement(zone, labels, pos), each_(NULL), subject_(NULL) {}

src/messages.h

@@ -71,7 +71,6 @@ class CallSite {
   int32_t pos_;
 };
 
-
 #define MESSAGE_TEMPLATES(T)                                                   \
   /* Error */                                                                  \
   T(None, "")                                                                  \
@@ -387,12 +386,10 @@ class CallSite {
   T(DuplicateExport, "Duplicate export of '%'")                                \
   T(DuplicateProto,                                                            \
     "Duplicate __proto__ fields are not allowed in object literals")           \
-  T(ForInLoopInitializer,                                                      \
-    "for-in loop variable declaration may not have an initializer.")           \
+  T(ForInOfLoopInitializer,                                                    \
+    "% loop variable declaration may not have an initializer.")                \
   T(ForInOfLoopMultiBindings,                                                  \
     "Invalid left-hand side in % loop: Must have a single binding.")           \
-  T(ForOfLoopInitializer,                                                      \
-    "for-of loop variable declaration may not have an initializer.")           \
   T(IllegalAccess, "Illegal access")                                           \
   T(IllegalBreak, "Illegal break statement")                                   \
   T(IllegalContinue, "Illegal continue statement")                             \

src/parsing/parser.cc

@@ -3331,9 +3331,8 @@ void Parser::InitializeForEachStatement(ForEachStatement* stmt,
   }
 }
 
-
 Statement* Parser::DesugarLexicalBindingsInForStatement(
-    Scope* inner_scope, bool is_const, ZoneList<const AstRawString*>* names,
+    Scope* inner_scope, VariableMode mode, ZoneList<const AstRawString*>* names,
     ForStatement* loop, Statement* init, Expression* cond, Statement* next,
     Statement* body, bool* ok) {
   // ES6 13.7.4.8 specifies that on each loop iteration the let variables are
@@ -3438,7 +3437,6 @@ Statement* Parser::DesugarLexicalBindingsInForStatement(
     ZoneList<Variable*> inner_vars(names->length(), zone());
     // For each let variable x:
     //    make statement: let/const x = temp_x.
-    VariableMode mode = is_const ? CONST : LET;
     for (int i = 0; i < names->length(); i++) {
       VariableProxy* proxy = NewUnresolved(names->at(i), mode);
       Declaration* declaration = factory()->NewVariableDeclaration(
@@ -3588,7 +3586,6 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
   //   'for' '(' Expression? ';' Expression? ';' Expression? ')' Statement
 
   int stmt_pos = peek_position();
-  bool is_const = false;
   Statement* init = NULL;
   ZoneList<const AstRawString*> lexical_bindings(1, zone());
 
@@ -3605,22 +3602,18 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
     if (peek() == Token::VAR || (peek() == Token::CONST && allow_const()) ||
         (peek() == Token::LET && IsNextLetKeyword())) {
       ParseVariableDeclarations(kForStatement, &parsing_result, CHECK_OK);
-      is_const = parsing_result.descriptor.mode == CONST;
 
-      int num_decl = parsing_result.declarations.length();
-      bool accept_IN = num_decl >= 1;
       ForEachStatement::VisitMode mode;
       int each_beg_pos = scanner()->location().beg_pos;
       int each_end_pos = scanner()->location().end_pos;
 
-      if (accept_IN && CheckInOrOf(&mode, ok)) {
+      if (CheckInOrOf(&mode, ok)) {
         if (!*ok) return nullptr;
-        if (num_decl != 1) {
-          const char* loop_type =
-              mode == ForEachStatement::ITERATE ? "for-of" : "for-in";
+        if (parsing_result.declarations.length() != 1) {
           ParserTraits::ReportMessageAt(
               parsing_result.bindings_loc,
-              MessageTemplate::kForInOfLoopMultiBindings, loop_type);
+              MessageTemplate::kForInOfLoopMultiBindings,
+              ForEachStatement::VisitModeString(mode));
           *ok = false;
           return nullptr;
         }
@@ -3630,14 +3623,10 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
             (is_strict(language_mode()) || mode == ForEachStatement::ITERATE ||
              IsLexicalVariableMode(parsing_result.descriptor.mode) ||
              !decl.pattern->IsVariableProxy())) {
-          if (mode == ForEachStatement::ITERATE) {
-            ReportMessageAt(parsing_result.first_initializer_loc,
-                            MessageTemplate::kForOfLoopInitializer);
-          } else {
-            // TODO(caitp): This should be an error in sloppy mode too.
-            ReportMessageAt(parsing_result.first_initializer_loc,
-                            MessageTemplate::kForInLoopInitializer);
-          }
+          ParserTraits::ReportMessageAt(
+              parsing_result.first_initializer_loc,
+              MessageTemplate::kForInOfLoopInitializer,
+              ForEachStatement::VisitModeString(mode));
           *ok = false;
           return nullptr;
         }
@@ -3895,8 +3884,8 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
   if (lexical_bindings.length() > 0) {
     BlockState block_state(&scope_, for_scope);
     result = DesugarLexicalBindingsInForStatement(
-                 inner_scope, is_const, &lexical_bindings, loop, init, cond,
-                 next, body, CHECK_OK);
+        inner_scope, parsing_result.descriptor.mode, &lexical_bindings, loop,
+        init, cond, next, body, CHECK_OK);
     for_scope->set_end_position(scanner()->location().end_pos);
   } else {
     for_scope->set_end_position(scanner()->location().end_pos);

src/parsing/parser.h

@@ -917,9 +917,9 @@ class Parser : public ParserBase<ParserTraits> {
                                   Expression* subject, Statement* body,
                                   bool is_destructuring);
   Statement* DesugarLexicalBindingsInForStatement(
-      Scope* inner_scope, bool is_const, ZoneList<const AstRawString*>* names,
-      ForStatement* loop, Statement* init, Expression* cond, Statement* next,
-      Statement* body, bool* ok);
+      Scope* inner_scope, VariableMode mode,
+      ZoneList<const AstRawString*>* names, ForStatement* loop, Statement* init,
+      Expression* cond, Statement* next, Statement* body, bool* ok);
 
   void RewriteDoExpression(Expression* expr, bool* ok);
 

src/parsing/preparser.cc

@@ -924,29 +924,21 @@ PreParser::Statement PreParser::ParseForStatement(bool* ok) {
       ParseVariableDeclarations(kForStatement, &decl_count, &is_lexical,
                                 &is_binding_pattern, &first_initializer_loc,
                                 &bindings_loc, CHECK_OK);
-      bool accept_IN = decl_count >= 1;
-      if (accept_IN && CheckInOrOf(&mode, ok)) {
+      if (CheckInOrOf(&mode, ok)) {
         if (!*ok) return Statement::Default();
         if (decl_count != 1) {
-          const char* loop_type =
-              mode == ForEachStatement::ITERATE ? "for-of" : "for-in";
           PreParserTraits::ReportMessageAt(
               bindings_loc, MessageTemplate::kForInOfLoopMultiBindings,
-              loop_type);
+              ForEachStatement::VisitModeString(mode));
           *ok = false;
           return Statement::Default();
         }
         if (first_initializer_loc.IsValid() &&
             (is_strict(language_mode()) || mode == ForEachStatement::ITERATE ||
              is_lexical || is_binding_pattern)) {
-          if (mode == ForEachStatement::ITERATE) {
-            ReportMessageAt(first_initializer_loc,
-                            MessageTemplate::kForOfLoopInitializer);
-          } else {
-            // TODO(caitp): This should be an error in sloppy mode, too.
-            ReportMessageAt(first_initializer_loc,
-                            MessageTemplate::kForInLoopInitializer);
-          }
+          PreParserTraits::ReportMessageAt(
+              first_initializer_loc, MessageTemplate::kForInOfLoopInitializer,
+              ForEachStatement::VisitModeString(mode));
           *ok = false;
           return Statement::Default();
         }