This patch implements an alternative approach to the rewriting

of non-pattern expressions, according to the (internally circulated)
design document.  Details to be provided here.

1.  RewritableAssignmentExpression has been renamed to RewritableExpression.
    It is a wrapper for AST nodes that wait for some potential rewriting
    (that may or may not happen).  Also, Is... and As... macros now see
    through RewritableExpressions.

2.  The function state keeps a list of rewritable expressions that must be
    rewritten only if they are used as non-pattern expressions.

3.  Expression classifiers are now templates, parameterized by parser
    traits.  They keep some additional state: a pointer to the list of
    non-pattern rewritable expressions.  It is important that expression
    classifiers be used strictly in a stack fashion, from now on.

4.  The RewriteNonPattern function has been simplified.

BUG=chromium:579913
LOG=N

Committed: https://crrev.com/7f5c864a6faf2b957b7273891e143b9bde35487c
Cr-Commit-Position: refs/heads/master@{#34154}

Review URL: https://codereview.chromium.org/1702063002

Cr-Commit-Position: refs/heads/master@{#34162}

src/ast/ast-expression-rewriter.cc

@@ -398,10 +398,10 @@ void AstExpressionRewriter::VisitDoExpression(DoExpression* node) {
 }
 
 
-void AstExpressionRewriter::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* node) {
+void AstExpressionRewriter::VisitRewritableExpression(
+    RewritableExpression* node) {
   REWRITE_THIS(node);
-  AST_REWRITE_PROPERTY(Expression, node, expression);
+  AST_REWRITE(Expression, node->expression(), node->Rewrite(replacement));
 }
 
 

src/ast/ast-expression-visitor.cc

@@ -400,8 +400,8 @@ void AstExpressionVisitor::VisitSuperCallReference(SuperCallReference* expr) {
 }
 
 
-void AstExpressionVisitor::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* expr) {
+void AstExpressionVisitor::VisitRewritableExpression(
+    RewritableExpression* expr) {
   VisitExpression(expr);
   RECURSE(Visit(expr->expression()));
 }

src/ast/ast-literal-reindexer.cc

@@ -77,8 +77,8 @@ void AstLiteralReindexer::VisitSuperCallReference(SuperCallReference* node) {
 }
 
 
-void AstLiteralReindexer::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* node) {
+void AstLiteralReindexer::VisitRewritableExpression(
+    RewritableExpression* node) {
   Visit(node->expression());
 }
 

src/ast/ast-numbering.cc

@@ -554,10 +554,10 @@ void AstNumberingVisitor::VisitFunctionLiteral(FunctionLiteral* node) {
 }
 
 
-void AstNumberingVisitor::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* node) {
+void AstNumberingVisitor::VisitRewritableExpression(
+    RewritableExpression* node) {
   IncrementNodeCount();
-  node->set_base_id(ReserveIdRange(RewritableAssignmentExpression::num_ids()));
+  node->set_base_id(ReserveIdRange(RewritableExpression::num_ids()));
   Visit(node->expression());
 }
 

src/ast/ast.h

@@ -91,7 +91,7 @@ namespace internal {
   V(CaseClause)                 \
   V(EmptyParentheses)           \
   V(DoExpression)               \
-  V(RewritableAssignmentExpression)
+  V(RewritableExpression)
 
 #define AST_NODE_LIST(V)                        \
   DECLARATION_NODE_LIST(V)                      \
@@ -205,13 +205,9 @@ class AstNode: public ZoneObject {
 
   // Type testing & conversion functions overridden by concrete subclasses.
 #define DECLARE_NODE_FUNCTIONS(type) \
-  bool Is##type() const { return node_type() == AstNode::k##type; } \
-  type* As##type() { \
-    return Is##type() ? reinterpret_cast<type*>(this) : NULL; \
-  } \
-  const type* As##type() const { \
-    return Is##type() ? reinterpret_cast<const type*>(this) : NULL; \
-  }
+  V8_INLINE bool Is##type() const;   \
+  V8_INLINE type* As##type();        \
+  V8_INLINE const type* As##type() const;
   AST_NODE_LIST(DECLARE_NODE_FUNCTIONS)
 #undef DECLARE_NODE_FUNCTIONS
 
@@ -2486,18 +2482,32 @@ class Assignment final : public Expression {
 };
 
 
-class RewritableAssignmentExpression : public Expression {
+// The RewritableExpression class is a wrapper for AST nodes that wait
+// for some potential rewriting.  However, even if such nodes are indeed
+// rewritten, the RewritableExpression wrapper nodes will survive in the
+// final AST and should be just ignored, i.e., they should be treated as
+// equivalent to the wrapped nodes.  For this reason and to simplify later
+// phases, RewritableExpressions are considered as exceptions of AST nodes
+// in the following sense:
+//
+// 1. IsRewritableExpression and AsRewritableExpression behave as usual.
+// 2. All other Is* and As* methods are practically delegated to the
+//    wrapped node, i.e. IsArrayLiteral() will return true iff the
+//    wrapped node is an array literal.
+//
+// Furthermore, an invariant that should be respected is that the wrapped
+// node is not a RewritableExpression.
+class RewritableExpression : public Expression {
  public:
-  DECLARE_NODE_TYPE(RewritableAssignmentExpression)
+  DECLARE_NODE_TYPE(RewritableExpression)
 
-  Expression* expression() { return expr_; }
+  Expression* expression() const { return expr_; }
   bool is_rewritten() const { return is_rewritten_; }
 
-  void set_expression(Expression* e) { expr_ = e; }
-
   void Rewrite(Expression* new_expression) {
     DCHECK(!is_rewritten());
     DCHECK_NOT_NULL(new_expression);
+    DCHECK(!new_expression->IsRewritableExpression());
     expr_ = new_expression;
     is_rewritten_ = true;
   }
@@ -2505,10 +2515,12 @@ class RewritableAssignmentExpression : public Expression {
   static int num_ids() { return parent_num_ids(); }
 
  protected:
-  RewritableAssignmentExpression(Zone* zone, Expression* expression)
+  RewritableExpression(Zone* zone, Expression* expression)
       : Expression(zone, expression->position()),
         is_rewritten_(false),
-        expr_(expression) {}
+        expr_(expression) {
+    DCHECK(!expression->IsRewritableExpression());
+  }
 
  private:
   int local_id(int n) const { return base_id() + parent_num_ids() + n; }
@@ -3365,12 +3377,9 @@ class AstNodeFactory final BASE_EMBEDDED {
         local_zone_, condition, then_expression, else_expression, position);
   }
 
-  RewritableAssignmentExpression* NewRewritableAssignmentExpression(
-      Expression* expression) {
+  RewritableExpression* NewRewritableExpression(Expression* expression) {
     DCHECK_NOT_NULL(expression);
-    DCHECK(expression->IsAssignment());
-    return new (local_zone_)
-        RewritableAssignmentExpression(local_zone_, expression);
+    return new (local_zone_) RewritableExpression(local_zone_, expression);
   }
 
   Assignment* NewAssignment(Token::Value op,
@@ -3508,6 +3517,46 @@ class AstNodeFactory final BASE_EMBEDDED {
 };
 
 
+// Type testing & conversion functions overridden by concrete subclasses.
+// Inline functions for AstNode.
+
+#define DECLARE_NODE_FUNCTIONS(type)                                          \
+  bool AstNode::Is##type() const {                                            \
+    NodeType mine = node_type();                                              \
+    if (mine == AstNode::kRewritableExpression &&                             \
+        AstNode::k##type != AstNode::kRewritableExpression)                   \
+      mine = reinterpret_cast<const RewritableExpression*>(this)              \
+                 ->expression()                                               \
+                 ->node_type();                                               \
+    return mine == AstNode::k##type;                                          \
+  }                                                                           \
+  type* AstNode::As##type() {                                                 \
+    NodeType mine = node_type();                                              \
+    AstNode* result = this;                                                   \
+    if (mine == AstNode::kRewritableExpression &&                             \
+        AstNode::k##type != AstNode::kRewritableExpression) {                 \
+      result =                                                                \
+          reinterpret_cast<const RewritableExpression*>(this)->expression();  \
+      mine = result->node_type();                                             \
+    }                                                                         \
+    return mine == AstNode::k##type ? reinterpret_cast<type*>(result) : NULL; \
+  }                                                                           \
+  const type* AstNode::As##type() const {                                     \
+    NodeType mine = node_type();                                              \
+    const AstNode* result = this;                                             \
+    if (mine == AstNode::kRewritableExpression &&                             \
+        AstNode::k##type != AstNode::kRewritableExpression) {                 \
+      result =                                                                \
+          reinterpret_cast<const RewritableExpression*>(this)->expression();  \
+      mine = result->node_type();                                             \
+    }                                                                         \
+    return mine == AstNode::k##type ? reinterpret_cast<const type*>(result)   \
+                                    : NULL;                                   \
+  }
+AST_NODE_LIST(DECLARE_NODE_FUNCTIONS)
+#undef DECLARE_NODE_FUNCTIONS
+
+
 }  // namespace internal
 }  // namespace v8
 

src/ast/prettyprinter.cc

@@ -412,8 +412,7 @@ void CallPrinter::VisitSuperCallReference(SuperCallReference* node) {
 }
 
 
-void CallPrinter::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* node) {
+void CallPrinter::VisitRewritableExpression(RewritableExpression* node) {
   Find(node->expression());
 }
 
@@ -929,8 +928,7 @@ void PrettyPrinter::VisitSuperCallReference(SuperCallReference* node) {
 }
 
 
-void PrettyPrinter::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* node) {
+void PrettyPrinter::VisitRewritableExpression(RewritableExpression* node) {
   Visit(node->expression());
 }
 
@@ -1705,8 +1703,7 @@ void AstPrinter::VisitSuperCallReference(SuperCallReference* node) {
 }
 
 
-void AstPrinter::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* node) {
+void AstPrinter::VisitRewritableExpression(RewritableExpression* node) {
   Visit(node->expression());
 }
 

src/compiler/ast-graph-builder.cc

@@ -3062,8 +3062,7 @@ VectorSlotPair AstGraphBuilder::CreateVectorSlotPair(
 }
 
 
-void AstGraphBuilder::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* node) {
+void AstGraphBuilder::VisitRewritableExpression(RewritableExpression* node) {
   Visit(node->expression());
 }
 

src/compiler/ast-loop-assignment-analyzer.cc

@@ -287,8 +287,7 @@ void ALAA::VisitCountOperation(CountOperation* e) {
 }
 
 
-void ALAA::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* expr) {
+void ALAA::VisitRewritableExpression(RewritableExpression* expr) {
   Visit(expr->expression());
 }
 

src/crankshaft/hydrogen.cc

@@ -12194,8 +12194,8 @@ void HOptimizedGraphBuilder::VisitExportDeclaration(
 }
 
 
-void HOptimizedGraphBuilder::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* node) {
+void HOptimizedGraphBuilder::VisitRewritableExpression(
+    RewritableExpression* node) {
   CHECK_ALIVE(Visit(node->expression()));
 }
 

src/crankshaft/typing.cc

@@ -770,8 +770,7 @@ void AstTyper::VisitSuperPropertyReference(SuperPropertyReference* expr) {}
 void AstTyper::VisitSuperCallReference(SuperCallReference* expr) {}
 
 
-void AstTyper::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* expr) {
+void AstTyper::VisitRewritableExpression(RewritableExpression* expr) {
   Visit(expr->expression());
 }
 

src/full-codegen/full-codegen.cc

@@ -1507,8 +1507,7 @@ void FullCodeGenerator::VisitEmptyParentheses(EmptyParentheses* expr) {
 }
 
 
-void FullCodeGenerator::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* expr) {
+void FullCodeGenerator::VisitRewritableExpression(RewritableExpression* expr) {
   Visit(expr->expression());
 }
 

src/interpreter/bytecode-generator.cc

@@ -2860,8 +2860,7 @@ void BytecodeGenerator::VisitLogicalAndExpression(BinaryOperation* binop) {
 }
 
 
-void BytecodeGenerator::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* expr) {
+void BytecodeGenerator::VisitRewritableExpression(RewritableExpression* expr) {
   Visit(expr->expression());
 }
 

src/parsing/expression-classifier.h

@@ -13,6 +13,7 @@ namespace v8 {
 namespace internal {
 
 
+template <typename Traits>
 class ExpressionClassifier {
  public:
   struct Error {
@@ -55,15 +56,25 @@ class ExpressionClassifier {
 
   enum FunctionProperties { NonSimpleParameter = 1 << 0 };
 
-  ExpressionClassifier()
-      : invalid_productions_(0),
+  explicit ExpressionClassifier(const Traits* t)
+      : zone_(t->zone()),
+        non_patterns_to_rewrite_(t->GetNonPatternList()),
+        invalid_productions_(0),
         function_properties_(0),
-        duplicate_finder_(nullptr) {}
+        duplicate_finder_(nullptr) {
+    non_pattern_begin_ = non_patterns_to_rewrite_->length();
+  }
 
-  explicit ExpressionClassifier(DuplicateFinder* duplicate_finder)
-      : invalid_productions_(0),
+  ExpressionClassifier(const Traits* t, DuplicateFinder* duplicate_finder)
+      : zone_(t->zone()),
+        non_patterns_to_rewrite_(t->GetNonPatternList()),
+        invalid_productions_(0),
         function_properties_(0),
-        duplicate_finder_(duplicate_finder) {}
+        duplicate_finder_(duplicate_finder) {
+    non_pattern_begin_ = non_patterns_to_rewrite_->length();
+  }
+
+  ~ExpressionClassifier() { Discard(); }
 
   bool is_valid(unsigned productions) const {
     return (invalid_productions_ & productions) == 0;
@@ -281,12 +292,14 @@ class ExpressionClassifier {
     assignment_pattern_error_ = Error();
   }
 
-  void Accumulate(const ExpressionClassifier& inner,
-                  unsigned productions = StandardProductions) {
+  void Accumulate(ExpressionClassifier* inner,
+                  unsigned productions = StandardProductions,
+                  bool merge_non_patterns = true) {
+    if (merge_non_patterns) MergeNonPatterns(inner);
     // Propagate errors from inner, but don't overwrite already recorded
     // errors.
     unsigned non_arrow_inner_invalid_productions =
-        inner.invalid_productions_ & ~ArrowFormalParametersProduction;
+        inner->invalid_productions_ & ~ArrowFormalParametersProduction;
     if (non_arrow_inner_invalid_productions == 0) return;
     unsigned non_arrow_productions =
         productions & ~ArrowFormalParametersProduction;
@@ -296,27 +309,27 @@ class ExpressionClassifier {
     if (errors != 0) {
       invalid_productions_ |= errors;
       if (errors & ExpressionProduction)
-        expression_error_ = inner.expression_error_;
+        expression_error_ = inner->expression_error_;
       if (errors & FormalParameterInitializerProduction)
         formal_parameter_initializer_error_ =
-            inner.formal_parameter_initializer_error_;
+            inner->formal_parameter_initializer_error_;
       if (errors & BindingPatternProduction)
-        binding_pattern_error_ = inner.binding_pattern_error_;
+        binding_pattern_error_ = inner->binding_pattern_error_;
       if (errors & AssignmentPatternProduction)
-        assignment_pattern_error_ = inner.assignment_pattern_error_;
+        assignment_pattern_error_ = inner->assignment_pattern_error_;
       if (errors & DistinctFormalParametersProduction)
         duplicate_formal_parameter_error_ =
-            inner.duplicate_formal_parameter_error_;
+            inner->duplicate_formal_parameter_error_;
       if (errors & StrictModeFormalParametersProduction)
         strict_mode_formal_parameter_error_ =
-            inner.strict_mode_formal_parameter_error_;
+            inner->strict_mode_formal_parameter_error_;
       if (errors & StrongModeFormalParametersProduction)
         strong_mode_formal_parameter_error_ =
-            inner.strong_mode_formal_parameter_error_;
+            inner->strong_mode_formal_parameter_error_;
       if (errors & LetPatternProduction)
-        let_pattern_error_ = inner.let_pattern_error_;
+        let_pattern_error_ = inner->let_pattern_error_;
       if (errors & CoverInitializedNameProduction)
-        cover_initialized_name_error_ = inner.cover_initialized_name_error_;
+        cover_initialized_name_error_ = inner->cover_initialized_name_error_;
     }
 
     // As an exception to the above, the result continues to be a valid arrow
@@ -325,16 +338,31 @@ class ExpressionClassifier {
         is_valid_arrow_formal_parameters()) {
       // Also copy function properties if expecting an arrow function
       // parameter.
-      function_properties_ |= inner.function_properties_;
+      function_properties_ |= inner->function_properties_;
 
-      if (!inner.is_valid_binding_pattern()) {
+      if (!inner->is_valid_binding_pattern()) {
         invalid_productions_ |= ArrowFormalParametersProduction;
-        arrow_formal_parameters_error_ = inner.binding_pattern_error_;
+        arrow_formal_parameters_error_ = inner->binding_pattern_error_;
       }
     }
   }
 
+  V8_INLINE int GetNonPatternBegin() const { return non_pattern_begin_; }
+
+  V8_INLINE void Discard() {
+    DCHECK_LE(non_pattern_begin_, non_patterns_to_rewrite_->length());
+    non_patterns_to_rewrite_->Rewind(non_pattern_begin_);
+  }
+
+  V8_INLINE void MergeNonPatterns(ExpressionClassifier* inner) {
+    DCHECK_LE(non_pattern_begin_, inner->non_pattern_begin_);
+    inner->non_pattern_begin_ = inner->non_patterns_to_rewrite_->length();
+  }
+
  private:
+  Zone* zone_;
+  ZoneList<typename Traits::Type::Expression>* non_patterns_to_rewrite_;
+  int non_pattern_begin_;
   unsigned invalid_productions_;
   unsigned function_properties_;
   Error expression_error_;
@@ -350,6 +378,7 @@ class ExpressionClassifier {
   DuplicateFinder* duplicate_finder_;
 };
 
+
 }  // namespace internal
 }  // namespace v8
 

src/parsing/parser.h

@@ -335,6 +335,9 @@ class ParserTraits {
 
     typedef v8::internal::AstProperties AstProperties;
 
+    typedef v8::internal::ExpressionClassifier<ParserTraits>
+        ExpressionClassifier;
+
     // Return types for traversing functions.
     typedef const AstRawString* Identifier;
     typedef v8::internal::Expression* Expression;
@@ -549,7 +552,7 @@ class ParserTraits {
                                     int initializer_end_position, bool is_rest);
   V8_INLINE void DeclareFormalParameter(
       Scope* scope, const ParserFormalParameters::Parameter& parameter,
-      ExpressionClassifier* classifier);
+      Type::ExpressionClassifier* classifier);
   void ParseArrowFunctionFormalParameters(ParserFormalParameters* parameters,
                                           Expression* params,
                                           const Scanner::Location& params_loc,
@@ -643,6 +646,7 @@ class ParserTraits {
 
   V8_INLINE void QueueDestructuringAssignmentForRewriting(
       Expression* assignment);
+  V8_INLINE void QueueNonPatternForRewriting(Expression* expr);
 
   void SetFunctionNameFromPropertyName(ObjectLiteralProperty* property,
                                        const AstRawString* name);
@@ -651,12 +655,13 @@ class ParserTraits {
                                         Expression* identifier);
 
   // Rewrite expressions that are not used as patterns
-  V8_INLINE Expression* RewriteNonPattern(
-      Expression* expr, const ExpressionClassifier* classifier, bool* ok);
-  V8_INLINE ObjectLiteralProperty* RewriteNonPatternObjectLiteralProperty(
-      ObjectLiteralProperty* property, const ExpressionClassifier* classifier,
+  V8_INLINE void RewriteNonPattern(Type::ExpressionClassifier* classifier,
                                    bool* ok);
 
+  V8_INLINE Zone* zone() const;
+
+  V8_INLINE ZoneList<Expression*>* GetNonPatternList() const;
+
   Expression* RewriteYieldStar(
       Expression* generator, Expression* expression, int pos);
 
@@ -812,8 +817,9 @@ class Parser : public ParserBase<ParserTraits> {
         const DeclarationParsingResult::Declaration* declaration,
         ZoneList<const AstRawString*>* names, bool* ok);
 
-    static void RewriteDestructuringAssignment(
-        Parser* parser, RewritableAssignmentExpression* expr, Scope* Scope);
+    static void RewriteDestructuringAssignment(Parser* parser,
+                                               RewritableExpression* expr,
+                                               Scope* Scope);
 
     static Expression* RewriteDestructuringAssignment(Parser* parser,
                                                       Assignment* assignment,
@@ -1029,11 +1035,7 @@ class Parser : public ParserBase<ParserTraits> {
   friend class NonPatternRewriter;
   V8_INLINE Expression* RewriteSpreads(ArrayLiteral* lit);
 
-  V8_INLINE Expression* RewriteNonPattern(
-      Expression* expr, const ExpressionClassifier* classifier, bool* ok);
-  V8_INLINE ObjectLiteralProperty* RewriteNonPatternObjectLiteralProperty(
-      ObjectLiteralProperty* property, const ExpressionClassifier* classifier,
-      bool* ok);
+  V8_INLINE void RewriteNonPattern(ExpressionClassifier* classifier, bool* ok);
 
   friend class InitializerRewriter;
   void RewriteParameterInitializer(Expression* expr, Scope* scope);
@@ -1184,7 +1186,7 @@ void ParserTraits::AddFormalParameter(ParserFormalParameters* parameters,
 
 void ParserTraits::DeclareFormalParameter(
     Scope* scope, const ParserFormalParameters::Parameter& parameter,
-    ExpressionClassifier* classifier) {
+    Type::ExpressionClassifier* classifier) {
   bool is_duplicate = false;
   bool is_simple = classifier->is_simple_parameter_list();
   auto name = is_simple || parameter.is_rest

src/parsing/pattern-rewriter.cc

@@ -33,7 +33,7 @@ void Parser::PatternRewriter::DeclareAndInitializeVariables(
 
 
 void Parser::PatternRewriter::RewriteDestructuringAssignment(
-    Parser* parser, RewritableAssignmentExpression* to_rewrite, Scope* scope) {
+    Parser* parser, RewritableExpression* to_rewrite, Scope* scope) {
   PatternRewriter rewriter;
 
   DCHECK(!to_rewrite->is_rewritten());
@@ -58,8 +58,7 @@ Expression* Parser::PatternRewriter::RewriteDestructuringAssignment(
     Parser* parser, Assignment* assignment, Scope* scope) {
   DCHECK_NOT_NULL(assignment);
   DCHECK_EQ(Token::ASSIGN, assignment->op());
-  auto to_rewrite =
-      parser->factory()->NewRewritableAssignmentExpression(assignment);
+  auto to_rewrite = parser->factory()->NewRewritableExpression(assignment);
   RewriteDestructuringAssignment(parser, to_rewrite, scope);
   return to_rewrite->expression();
 }
@@ -91,8 +90,8 @@ Parser::PatternRewriter::SetInitializerContextIfNeeded(Expression* node) {
   // AssignmentElement nodes
   PatternContext old_context = context();
   bool is_destructuring_assignment =
-      node->IsRewritableAssignmentExpression() &&
-      !node->AsRewritableAssignmentExpression()->is_rewritten();
+      node->IsRewritableExpression() &&
+      !node->AsRewritableExpression()->is_rewritten();
   bool is_assignment =
       node->IsAssignment() && node->AsAssignment()->op() == Token::ASSIGN;
   if (is_destructuring_assignment || is_assignment) {
@@ -324,10 +323,11 @@ Variable* Parser::PatternRewriter::CreateTempVar(Expression* value) {
 }
 
 
-void Parser::PatternRewriter::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* node) {
-  if (!IsAssignmentContext()) {
-    // Mark the assignment as rewritten to prevent redundant rewriting, and
+void Parser::PatternRewriter::VisitRewritableExpression(
+    RewritableExpression* node) {
+  // If this is not a destructuring assignment...
+  if (!IsAssignmentContext() || !node->expression()->IsAssignment()) {
+    // Mark the node as rewritten to prevent redundant rewriting, and
     // perform BindingPattern rewriting
     DCHECK(!node->is_rewritten());
     node->Rewrite(node->expression());

src/parsing/preparser.cc

@@ -573,7 +573,7 @@ PreParser::Statement PreParser::ParseVariableDeclarations(
     int decl_pos = peek_position();
     PreParserExpression pattern = PreParserExpression::Default();
     {
-      ExpressionClassifier pattern_classifier;
+      ExpressionClassifier pattern_classifier(this);
       Token::Value next = peek();
       pattern = ParsePrimaryExpression(&pattern_classifier, CHECK_OK);
 
@@ -594,7 +594,7 @@ PreParser::Statement PreParser::ParseVariableDeclarations(
     Scanner::Location variable_loc = scanner()->location();
     nvars++;
     if (Check(Token::ASSIGN)) {
-      ExpressionClassifier classifier;
+      ExpressionClassifier classifier(this);
       ParseAssignmentExpression(var_context != kForStatement, &classifier,
                                 CHECK_OK);
       ValidateExpression(&classifier, CHECK_OK);
@@ -648,7 +648,7 @@ PreParser::Statement PreParser::ParseExpressionOrLabelledStatement(bool* ok) {
           IsClassConstructor(function_state_->kind())) {
         bool is_this = peek() == Token::THIS;
         Expression expr = Expression::Default();
-        ExpressionClassifier classifier;
+        ExpressionClassifier classifier(this);
         if (is_this) {
           expr = ParseStrongInitializationExpression(&classifier, CHECK_OK);
         } else {
@@ -684,7 +684,7 @@ PreParser::Statement PreParser::ParseExpressionOrLabelledStatement(bool* ok) {
   }
 
   bool starts_with_identifier = peek_any_identifier();
-  ExpressionClassifier classifier;
+  ExpressionClassifier classifier(this);
   Expression expr = ParseExpression(true, &classifier, CHECK_OK);
   ValidateExpression(&classifier, CHECK_OK);
 
@@ -937,10 +937,9 @@ PreParser::Statement PreParser::ParseForStatement(bool* ok) {
         }
 
         if (mode == ForEachStatement::ITERATE) {
-          ExpressionClassifier classifier;
-          Expression enumerable =
+          ExpressionClassifier classifier(this);
           ParseAssignmentExpression(true, &classifier, CHECK_OK);
-          PreParserTraits::RewriteNonPattern(enumerable, &classifier, CHECK_OK);
+          RewriteNonPattern(&classifier, CHECK_OK);
         } else {
           ParseExpression(true, CHECK_OK);
         }
@@ -951,7 +950,7 @@ PreParser::Statement PreParser::ParseForStatement(bool* ok) {
       }
     } else {
       int lhs_beg_pos = peek_position();
-      ExpressionClassifier classifier;
+      ExpressionClassifier classifier(this);
       Expression lhs = ParseExpression(false, &classifier, CHECK_OK);
       int lhs_end_pos = scanner()->location().end_pos;
       is_let_identifier_expression =
@@ -976,10 +975,9 @@ PreParser::Statement PreParser::ParseForStatement(bool* ok) {
         }
 
         if (mode == ForEachStatement::ITERATE) {
-          ExpressionClassifier classifier;
-          Expression enumerable =
+          ExpressionClassifier classifier(this);
           ParseAssignmentExpression(true, &classifier, CHECK_OK);
-          PreParserTraits::RewriteNonPattern(enumerable, &classifier, CHECK_OK);
+          RewriteNonPattern(&classifier, CHECK_OK);
         } else {
           ParseExpression(true, CHECK_OK);
         }
@@ -1057,7 +1055,7 @@ PreParser::Statement PreParser::ParseTryStatement(bool* ok) {
   if (tok == Token::CATCH) {
     Consume(Token::CATCH);
     Expect(Token::LPAREN, CHECK_OK);
-    ExpressionClassifier pattern_classifier;
+    ExpressionClassifier pattern_classifier(this);
     ParsePrimaryExpression(&pattern_classifier, CHECK_OK);
     ValidateBindingPattern(&pattern_classifier, CHECK_OK);
     Expect(Token::RPAREN, CHECK_OK);
@@ -1114,7 +1112,7 @@ PreParser::Expression PreParser::ParseFunctionLiteral(
   FunctionState function_state(&function_state_, &scope_, function_scope, kind,
                                &factory);
   DuplicateFinder duplicate_finder(scanner()->unicode_cache());
-  ExpressionClassifier formals_classifier(&duplicate_finder);
+  ExpressionClassifier formals_classifier(this, &duplicate_finder);
 
   Expect(Token::LPAREN, CHECK_OK);
   int start_position = scanner()->location().beg_pos;
@@ -1220,7 +1218,7 @@ PreParserExpression PreParser::ParseClassLiteral(
 
   bool has_extends = Check(Token::EXTENDS);
   if (has_extends) {
-    ExpressionClassifier classifier;
+    ExpressionClassifier classifier(this);
     ParseLeftHandSideExpression(&classifier, CHECK_OK);
     ValidateExpression(&classifier, CHECK_OK);
   }
@@ -1236,7 +1234,7 @@ PreParserExpression PreParser::ParseClassLiteral(
     bool is_computed_name = false;  // Classes do not care about computed
                                     // property names here.
     Identifier name;
-    ExpressionClassifier classifier;
+    ExpressionClassifier classifier(this);
     ParsePropertyDefinition(&checker, in_class, has_extends, is_static,
                             &is_computed_name, &has_seen_constructor,
                             &classifier, &name, CHECK_OK);
@@ -1260,7 +1258,7 @@ PreParser::Expression PreParser::ParseV8Intrinsic(bool* ok) {
   // Allow "eval" or "arguments" for backward compatibility.
   ParseIdentifier(kAllowRestrictedIdentifiers, CHECK_OK);
   Scanner::Location spread_pos;
-  ExpressionClassifier classifier;
+  ExpressionClassifier classifier(this);
   ParseArguments(&spread_pos, &classifier, ok);
   ValidateExpression(&classifier, CHECK_OK);
 

src/parsing/preparser.h

@@ -197,8 +197,6 @@ class PreParserExpression {
            ExpressionTypeField::decode(code_) == kAssignment;
   }
 
-  bool IsRewritableAssignmentExpression() const { return IsAssignment(); }
-
   bool IsObjectLiteral() const {
     return TypeField::decode(code_) == kObjectLiteralExpression;
   }
@@ -487,8 +485,7 @@ class PreParserFactory {
                                           PreParserExpression right, int pos) {
     return PreParserExpression::Default();
   }
-  PreParserExpression NewRewritableAssignmentExpression(
-      PreParserExpression expression) {
+  PreParserExpression NewRewritableExpression(PreParserExpression expression) {
     return expression;
   }
   PreParserExpression NewAssignment(Token::Value op,
@@ -589,6 +586,9 @@ class PreParserTraits {
 
     typedef int AstProperties;
 
+    typedef v8::internal::ExpressionClassifier<PreParserTraits>
+        ExpressionClassifier;
+
     // Return types for traversing functions.
     typedef PreParserIdentifier Identifier;
     typedef PreParserExpression Expression;
@@ -885,7 +885,7 @@ class PreParserTraits {
     ++parameters->arity;
   }
   void DeclareFormalParameter(Scope* scope, PreParserIdentifier parameter,
-                              ExpressionClassifier* classifier) {
+                              Type::ExpressionClassifier* classifier) {
     if (!classifier->is_simple_parameter_list()) {
       scope->SetHasNonSimpleParameters();
     }
@@ -923,19 +923,19 @@ class PreParserTraits {
   inline void RewriteDestructuringAssignments() {}
 
   inline void QueueDestructuringAssignmentForRewriting(PreParserExpression) {}
+  inline void QueueNonPatternForRewriting(PreParserExpression) {}
 
   void SetFunctionNameFromPropertyName(PreParserExpression,
                                        PreParserIdentifier) {}
   void SetFunctionNameFromIdentifierRef(PreParserExpression,
                                         PreParserExpression) {}
 
-  inline PreParserExpression RewriteNonPattern(
-      PreParserExpression expr, const ExpressionClassifier* classifier,
-      bool* ok);
-  inline PreParserExpression RewriteNonPatternObjectLiteralProperty(
-      PreParserExpression property, const ExpressionClassifier* classifier,
+  inline void RewriteNonPattern(Type::ExpressionClassifier* classifier,
                                 bool* ok);
 
+  V8_INLINE Zone* zone() const;
+  V8_INLINE ZoneList<PreParserExpression>* GetNonPatternList() const;
+
   inline PreParserExpression RewriteYieldStar(
       PreParserExpression generator, PreParserExpression expr, int pos);
 
@@ -1119,19 +1119,19 @@ PreParserExpression PreParserTraits::ParseDoExpression(bool* ok) {
 }
 
 
-PreParserExpression PreParserTraits::RewriteNonPattern(
-    PreParserExpression expr, const ExpressionClassifier* classifier,
+void PreParserTraits::RewriteNonPattern(Type::ExpressionClassifier* classifier,
                                         bool* ok) {
   pre_parser_->ValidateExpression(classifier, ok);
-  return expr;
 }
 
 
-PreParserExpression PreParserTraits::RewriteNonPatternObjectLiteralProperty(
-    PreParserExpression property, const ExpressionClassifier* classifier,
-    bool* ok) {
-  pre_parser_->ValidateExpression(classifier, ok);
-  return property;
+Zone* PreParserTraits::zone() const {
+  return pre_parser_->function_state_->scope()->zone();
+}
+
+
+ZoneList<PreParserExpression>* PreParserTraits::GetNonPatternList() const {
+  return pre_parser_->function_state_->non_patterns_to_rewrite();
 }
 
 

src/typing-asm.cc

@@ -1551,8 +1551,7 @@ void AsmTyper::VisitWithExpectation(Expression* expr, Type* expected_type,
 }
 
 
-void AsmTyper::VisitRewritableAssignmentExpression(
-    RewritableAssignmentExpression* expr) {
+void AsmTyper::VisitRewritableExpression(RewritableExpression* expr) {
   RECURSE(Visit(expr->expression()));
 }
 

src/wasm/asm-wasm-builder.cc

@@ -1177,10 +1177,7 @@ class AsmWasmBuilderImpl : public AstVisitor {
 
   void VisitDoExpression(DoExpression* expr) { UNREACHABLE(); }
 
-  void VisitRewritableAssignmentExpression(
-      RewritableAssignmentExpression* expr) {
-    UNREACHABLE();
-  }
+  void VisitRewritableExpression(RewritableExpression* expr) { UNREACHABLE(); }
 
   struct IndexContainer : public ZoneObject {
     uint16_t index;