Goal:
    A : Type  n : nat  P : A → bool  d : A  H : is_true true
  ============================
   (S n < 0 → ∃ x : A, d = x ∧ P x)


DEBUG:Going to execute:
try (solve [ inversion H ])
DEBUG LTAC Evaluated term: H
DEBUG LTAC Evaluated term: (is_true true)
Level 2: type of H
 has value 
(is_true true)