  --> [ local path prefix ]/top_ports/internal_port.fpp:26:3
   |
26 |   port c = c1.P
   |   ^^^^^^^^^^^^^ topology port cannot point to an internal port
   |
  ::: [ local path prefix ]/top_ports/internal_port.fpp:7:3
   |
 7 |   internal port P(x: U32)
   |   ----------------------- defined here

