Port struct is not acknowledged when empty

It seems like a port struct without any fields isn't seen as a port struct.

struct port A {}

#[no_mangle]
entity top() {
    let (a, b) = port;
    let _ = inst ding(a);
}

entity ding(x: A) { }

Results in

error: A port expression cannot create non-port values
  ┌─ src/playground.spade:5:18
  │
5 │     let (a, b) = port;
  │                  ^^^^ playground::playground::A is not a port type
  │
  = note: The port expression creates a (playground::playground::A, inv playground::playground::A)

Error: aborting due to previous error

Location:
    spade-compiler/src/main.rs:169:17