Goal:
    A : Type  P : A → A → Type  hd : A  hd' : A  tl : list A  p : P hd hd'
  ============================
   (hd :: tl = [] ++ hd :: tl)


DEBUG:Going to execute:
constructor 1
Level 3: evaluation returns
<coq-core.plugins.tauto::is_unit_or_eq@0>
where
tauto_flags := 
of type
tauto_flags
X1 := hd :: tl = [] ++ hd :: tl
of type
constr of type tacvalue