Goal:
    A : Type  B : Type  C : Type  R : A → B → C → Type
  ============================
   (NoConfusionHom_All3 A B C R [] [] [] All3_nil All3_nil
    → let H := CoreTactics.block in All3_nil = All3_nil)


DEBUG:Going to execute:
<coq-core.plugins.ltac::intro@0>