new classes: assert that constructors are not callable and rewrite 'return;'

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 4e1fb26c267496cbc4f3e4934fb017a589175b86..e457e66a215f1aed49d48e5c54ffed107b29cca9 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -2618,7 +2618,7 @@ class FunctionLiteral FINAL : public Expression {
   class HasDuplicateParameters : public BitField<ParameterFlag, 3, 1> {};
   class IsFunction : public BitField<IsFunctionFlag, 4, 1> {};
   class IsParenthesized : public BitField<IsParenthesizedFlag, 5, 1> {};
-  class FunctionKindBits : public BitField<FunctionKind, 6, 6> {};
+  class FunctionKindBits : public BitField<FunctionKind, 6, 7> {};
 };