Cannot resolve migration dropping a required property if a DML function is involved

[dnwpark]

When migrating from:

  type Foo {
    required a: str;
  }

  function insert_foo(data: json) -> Foo {
    using (
      insert Foo {
        a := <str>data['a'],
      }
    );
  };

to:

  type Foo {
  }

  function insert_foo(data: json) -> Foo {
    using (
      insert Foo {
      }
    );
  };

Using gel migration create to resolve the migration seems unable to figure out what to do.