Allow constructor and method signatures in classes

src/parsing/preparser.h

Index: src/parsing/preparser.h
diff --git a/src/parsing/preparser.h b/src/parsing/preparser.h
index aa0fe207c9f10293d0b055beb93fbfb2567884c9..2e2e36d98f504a96fcc21273a4afa3507d6b63e0 100644
--- a/src/parsing/preparser.h
+++ b/src/parsing/preparser.h
@@ -183,6 +183,12 @@ class PreParserExpression {
         ExpressionTypeField::encode(kNoTemplateTagExpression));
   }
 
+  static PreParserExpression Empty() {
+    return PreParserExpression(TypeField::encode(kEmptyExpression));
+  }
+
+  bool IsEmpty() const { return TypeField::decode(code_) == kEmptyExpression; }
+
   bool IsIdentifier() const {
     return TypeField::decode(code_) == kIdentifierExpression;
   }
@@ -282,6 +288,7 @@ class PreParserExpression {
  private:
   enum Type {
     kExpression,
+    kEmptyExpression,
     kIdentifierExpression,
     kStringLiteralExpression,
     kBinaryOperationExpression,
@@ -1005,7 +1012,7 @@ class PreParserTraits {
     return PreParserIdentifier::Default();
   }
   static PreParserExpression EmptyExpression() {
-    return PreParserExpression::Default();
+    return PreParserExpression::Empty();
   }
   static PreParserExpression EmptyLiteral() {
     return PreParserExpression::Default();
@@ -1059,6 +1066,9 @@ class PreParserTraits {
   static typesystem::PreParserTypeMember EmptyTypeMember() {
     return typesystem::PreParserTypeMember::Default(false, false);
   }
+  static bool IsEmptyExpression(const PreParserExpression& expression) {
+    return expression.IsEmpty();
+  }
 
   // Odd-ball literal creators.
   static PreParserExpression GetLiteralTheHole(int position,