Goal:
    A : Type  x : A  m : tree' A  a : A  H : xH <> xH
  ============================
   (Some x = Some a)


DEBUG:Going to execute:
congruence
DEBUG LTAC Evaluated term: gso0
Level 0: Backtrace:

In environment
A : Type
x : A
m : tree' A
a : A
H : xH <> xH
Unable to unify "get' ?M1991 (set0 ?M1992 ?M1993) = None" with
 "Some x = Some a".
Level 0: Backtrace:

In environment
A : Type
x : A
m : tree' A
a : A
H : xH <> xH
Unable to unify "get' ?M1991 (set0 ?M1992 ?M1993) = None" with
 "Some x = Some a".