Goal:
  
  G : t
  s0 : VSet.t
  s' : VSet.t
  x : V.t
  y : V.t
  z : V.t
  d : DisjointAdd x s0 s'
  e : EdgeOf x y
  a : SPath s0 y z
  s1 : VSet.t
  x0 : V.t
  H : False
  ============================
   ({|
      pr1 := {| pr1 := s'; pr2 := {| pr1 := x; pr2 := z |} |};
      pr2 := spath_step d e a
    |} =
    {|
      pr1 := {| pr1 := s1; pr2 := {| pr1 := x0; pr2 := x0 |} |};
      pr2 := spath_refl s1 x0
    |})


DEBUG:Going to execute:
destruct id
DEBUG LTAC Evaluated term: H
DEBUG LTAC Evaluated term: False
Level 6: type of H
 has value 
False

Level 6: Backtrace:

No matching clauses for match.
Level 5: Backtrace:

No matching clauses for match.
Level 5: evaluation
raised the exception
Backtrace:

No matching clauses for match.

Level 5: Backtrace:

No matching clauses for match.
Level 4: Backtrace:

No matching clauses for match.