Goal:
    y : t  H0 : False
  ============================
   (Eq = Lt)


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

In environment
y : t
H0 : False
Unable to unify "Lt" with "Eq".
Level 0: Backtrace:

In environment
y : t
H0 : False
Unable to unify "Lt" with "Eq".