Why is my code does not compile? (dmd 2.021 linux)

[Weed]

void main()
{
    int i;

    ref int func()
    {
      return i;
    }

    func() = 4;
}

lval.d(5): found 'ref' instead of statement
lval.d(10): no identifier for declarator func
lval.d(11): unrecognized declaration


but code like this compiles:

ref int func()
{
  int* i = new int;
  return *i;
}

void main()
{
    func() = 4;
}