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:
match H with
           | H' => fail 2
           | _ => unify X Y; clear H' || clear H
           end
Level 4: Backtrace:

In environment
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
Unable to unify "∀ l : list A, (∀ x : A, In x l → bool) → bool" with
 "list A".
Level 4: Backtrace:

In environment
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
Unable to unify "∀ l : list A, (∀ x : A, In x l → bool) → bool" with
 "list A".
Level 4: Backtrace:

In environment
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
Unable to unify "∀ l : list A, (∀ x : A, In x l → bool) → bool" with
 "list A".
Level 4: Backtrace:

In environment
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
Unable to unify "∀ l : list A, (∀ x : A, In x l → bool) → bool" with
 "list A".
Level 3: Backtrace:

In environment
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
Unable to unify "∀ l : list A, (∀ x : A, In x l → bool) → bool" with
 "list A".