Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  n : Z
  x : V.t
  y : V.t
  n0 : x = y -> False
  H : false = true
  ============================
   (x = y)


DEBUG:Going to execute:
constructor 1
Level 3: evaluation returns
<coq-core.plugins.tauto::is_unit_or_eq@0>
where
tauto_flags := 
of type
tauto_flags
X1 := x = y
of type
constr of type tacvalue