[es6] parse destructuring assignment

src/ast.h

 // 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.
 
 #ifndef V8_AST_H_
 #define V8_AST_H_
 
 #include "src/assembler.h"
 #include "src/ast-value-factory.h"
 #include "src/bailout-reason.h"
@@ skipping 350 matching lines @@
 
   // True iff the expression is the null literal.
   bool IsNullLiteral() const;
 
   // True if we can prove that the expression is the undefined literal.
   bool IsUndefinedLiteral(Isolate* isolate) const;
 
   // True iff the expression is a valid target for an assignment.
   bool IsValidReferenceExpressionOrThis() const;
 
+  bool IsPatternOrLiteral() const {
+    return IsObjectLiteral() || IsArrayLiteral();
+  }
+
   // Expression type bounds
   Bounds bounds() const { return bounds_; }
   void set_bounds(Bounds bounds) { bounds_ = bounds; }
 
   // Type feedback information for assignments and properties.
   virtual bool IsMonomorphic() {
     UNREACHABLE();
     return false;
   }
   virtual SmallMapList* GetReceiverTypes() {
@@ skipping 1968 matching lines @@
   Token::Value binary_op() const;
 
   Token::Value op() const { return TokenField::decode(bit_field_); }
   Expression* target() const { return target_; }
   Expression* value() const { return value_; }
   BinaryOperation* binary_operation() const { return binary_operation_; }
 
   // This check relies on the definition order of token in token.h.
   bool is_compound() const { return op() > Token::ASSIGN; }
 
+  // Returns true if op is `=` and LHS is might be a pattern
+  bool IsDestructuring() const {
+    return op() == Token::ASSIGN && target()->IsPatternOrLiteral();
+  }
+
   static int num_ids() { return parent_num_ids() + 2; }
   BailoutId AssignmentId() const { return BailoutId(local_id(0)); }
 
   // Type feedback information.
   TypeFeedbackId AssignmentFeedbackId() { return TypeFeedbackId(local_id(1)); }
   bool IsMonomorphic() override { return receiver_types_.length() == 1; }
   bool IsUninitialized() const {
     return IsUninitializedField::decode(bit_field_);
   }
   bool HasNoTypeInformation() {
@@ skipping 1266 matching lines @@
 
  private:
   Zone* zone_;
   AstValueFactory* ast_value_factory_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_