Goal:
    x : t  y : t  H : lt x y  H0 : lt y x  H1 : False
  ============================
   (Lt = Gt)


DEBUG:Going to execute:
Ltac.symmetry; trivial
Level 1: Backtrace:

In environment
x, y : t
H : lt x y
H0 : lt y x
H1 : False
Unable to unify "Gt" with "Lt".
Level 0: Backtrace:

In environment
x, y : t
H : lt x y
H0 : lt y x
H1 : False
Unable to unify "Gt" with "Lt".