Implement handling of arrow functions in the parser

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 3308fba540a8b2f826be0a08093e7d2f763a45a2..84d828ebb9d40ac7505dfe16b8b8e99332e1b644 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -344,6 +344,11 @@ class Expression : public AstNode {
   Bounds bounds() const { return bounds_; }
   void set_bounds(Bounds bounds) { bounds_ = bounds; }
 
+  // Whether the expression is parenthesized
+  unsigned parenthesization_level() const { return parenthesization_level_; }
+  bool is_parenthesized() const { return parenthesization_level_ > 0; }
+  void increase_parenthesization_level() { ++parenthesization_level_; }
+
   // Type feedback information for assignments and properties.
   virtual bool IsMonomorphic() {
     UNREACHABLE();
@@ -370,6 +375,7 @@ class Expression : public AstNode {
       : AstNode(pos),
         zone_(zone),
         bounds_(Bounds::Unbounded(zone)),
+        parenthesization_level_(0),
         id_(GetNextId(zone)),
         test_id_(GetNextId(zone)) {}
   void set_to_boolean_types(byte types) { to_boolean_types_ = types; }
@@ -379,6 +385,7 @@ class Expression : public AstNode {
  private:
   Bounds bounds_;
   byte to_boolean_types_;
+  unsigned parenthesization_level_;
 
   const BailoutId id_;
   const TypeFeedbackId test_id_;