Allow constructor and method signatures in classes

src/parsing/parser.h

Index: src/parsing/parser.h
diff --git a/src/parsing/parser.h b/src/parsing/parser.h
index 56966382a30633933d086c8722d2c30d76cc90e8..f3facb288e929973319e55791675c9e2635d4207 100644
--- a/src/parsing/parser.h
+++ b/src/parsing/parser.h
@@ -500,6 +500,7 @@ class ParserTraits {
   static Expression* EmptyExpression() {
     return NULL;
   }
+  static bool IsEmptyExpression(Expression* e) { return e == nullptr; }
   static Literal* EmptyLiteral() {
     return NULL;
   }