Goal:
    y : string  hc : Eq = Gt
  ============================
   (Eq = Lt)


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

In environment
y : string
hc : Eq = Gt
Unable to unify "Lt" with "Eq".
Level 0: Backtrace:

In environment
y : string
hc : Eq = Gt
Unable to unify "Lt" with "Eq".