Goal:
    A : Type  P : A → Type  Q : A → Type  Hl'1 : list A  Hl' : All Q Hl'1
  ============================
   ([] = Hl'1
    → let H := CoreTactics.block in
      let H0 := CoreTactics.block in All (λ x : A, P x × Q x) [])


DEBUG:Going to execute:
cbv beta iota delta [TODO projection TODO projection] in id, id'
DEBUG LTAC Evaluated term: Hl'1
DEBUG LTAC Evaluated term: (list A)
Level 3: type of id
 has value 
(list A)