 --> [ local path prefix ]/state_machine/undef/constant_error.fpp:2:16
  |
2 |   constant b = a
  |                ^ cannot find constant `a` in scope

 --> [ local path prefix ]/state_machine/undef/constant_error.fpp:1:15
  |
1 | state machine SM {
  |               ^^ state machine must have initial transition

