error: State1 + Event1: State and event combination specified multiple times, remove duplicates.
  --> tests/compile-fail/double_state_event.rs:5:1
   |
5  | / statemachine! {
6  | |     transitions: {
7  | |         *State1 + Event1 = State2,
8  | |         State1 + Event1 = State3, //~ State and event combination specified multiple times, remove duplicates.
9  | |     }
10 | | }
   | |_^
   |
   = note: this error originates in the macro `statemachine` (in Nightly builds, run with -Z macro-backtrace for more info)