Goal:
  
  A : Type
  forallb_InP : ∀ l : list A, (∀ x : A, In x l → bool) → bool
  x : A
  xs : list A
  H : ∀ x0 : A, In x0 (x :: xs) → bool
  ============================
   (x = x ∨ In x xs)


DEBUG:Going to execute:
<coq-core.plugins.ltac::unify@0> $1 $2
DEBUG LTAC Evaluated term: A
DEBUG LTAC Evaluated term: (list A)