Goal:
  
  A : Type
  i : positive
  x : A
  IHi : forall (m : tree' A) (j : positive),
        i <> j -> get' i (set' j x m) = get' i m
  m : tree' A
  a : A
  j : positive
  H : xI i <> xI j
  ============================
   (get' i (set0 j x) = None)


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

In environment
A : Type
i : positive
x : A
IHi : forall (m : tree' A) (j : positive),
      i <> j -> get' i (set' j x m) = get' i m
m : tree' A
a : A
j : positive
H : xI i <> xI j
Unable to unify "get' i (set' ?M1901 x ?M1900) = get' i ?M1900" with
 "get' i (set0 j x) = None".
Level 0: Backtrace:

In environment
A : Type
i : positive
x : A
IHi : forall (m : tree' A) (j : positive),
      i <> j -> get' i (set' j x m) = get' i m
m : tree' A
a : A
j : positive
H : xI i <> xI j
Unable to unify "get' i (set' ?M1901 x ?M1900) = get' i ?M1900" with
 "get' i (set0 j x) = None".