error: Duplicate transitions are not allowed!
  --> $DIR/dupe_transitions_fail.rs:5:1
   |
5  | / fsm! {
6  | |     name SimpleMachine; command SimpleMachineCommand; error Infallible;
7  | |
8  | |     One --(A)--> Two;
9  | |     One --(A)--> Two;
10 | | }
   | |_^
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)