(** A state can "crash the world" if it can make an observable transition whose trace is not accepted by the external world. *)
Definition can_crash_world (w: world) (S: state) : Prop :=
exists t, exists S', Csem.step ge S t S' /\ forall w', ~possible_trace w t w'.

Theorem not_imm_safe_t:
forall K C a m f k,
context K RV C ->
~imm_safe_t K a m ->
Csem.step ge (ExprState f (C a) k e m) E0 Stuckstate \/ can_crash_world w (ExprState f (C a) k e m).