Goal:
  
  A : Type
  B : Type
  t' : A
  P : B → A → A → Type
  b : B
  bs : list B
  hd : A
  tl : list A
  p : P b hd t'
  e : #|bs| = #|tl|
  ============================
   (Some hd = Some hd × (hd = t') + (∑ i' : B, Some b = Some i' × P i' hd t'))


DEBUG:Going to execute:
Ltac.split
Level 2: evaluation returns
<coq-core.plugins.tauto::is_conj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := Some hd = Some hd
      × (hd = t') + (∑ i' : B, Some b = Some i' × P i' hd t')
of type
constr of type tacvalue