Goal:
  
  A : Type
  B : Type
  R : A → B → Type
  R' : ∀ (a : A) (b : B), R a b → Type
  ============================
   (let H := CoreTactics.block in
    NoConfusionHom_All2_dep A B R R' [] [] All2_nil All2_dep_nil All2_dep_nil
    → let H0 := CoreTactics.block in All2_dep_nil = All2_dep_nil)


DEBUG:Going to execute:
match T with
           | context [ CoreTactics.block ] =>
               change T; CoreTactics.intros_until_block
           end