@Override
  default DfType correctForClosure() {
    DfReferenceType newType = dropLocality();
    if (newType.getMutability() == Mutability.MUST_NOT_MODIFY) {
      // If we must not modify parameter inside the method body itself,
      // we may still be able to modify it inside nested closures,
      // as they could be executed later.
      newType = newType.dropMutability();
    }
    return newType;
  }
@Override
  default DfType correctForClosure()