type
  File = record
    fd: Int
  end

  Map#[K, V] = record
    key: K;
    value: V
  end

  Cache#[K, V] = record(Map#[^Word8, V])
    newest: K
  end

var
  store: Cache#[^Int, ^File]
  byte_key: ^Word8
  upcast: ^Map#[^Word8, ^File]

proc put#[K2, V2](target: ^Map#[K2, V2]; key: K2)
begin
  target^.key := key
return

program()
begin
  upcast := @store;
  put(@store, byte_key)
return 0u8

end.