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
  j : positive
  H : xO i <> xO 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
j : positive
H : xO i <> xO j
Unable to unify "get' i (set' ?M1915 x ?M1914) = get' i ?M1914" 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
j : positive
H : xO i <> xO j
Unable to unify "get' i (set' ?M1915 x ?M1914) = get' i ?M1914" with
 "get' i (set0 j x) = None".