 --> [ local path prefix ]/state_machine/types/struct_undef_constant.fpp:2:37
  |
2 |   struct S { x: U32 } default { x = a }
  |                                     ^ cannot find constant `a` in scope

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

