Goal:
  
  A : Type
  P : A -> Prop
  b : A -> bool
  f : forall x : A, reflect (P x) (b x)
  x : A
  ============================
   (reflect (P x) (b x))


DEBUG:Going to execute:
solve
[ trivial
with eq_true
| Ltac.reflexivity
| Ltac.symmetry; trivial
| contradiction ]