Goal:
    G : t  HI : invariants  A : Prop  B : Prop  b : B  H0 : A -> B  H : A
  ============================
   A


DEBUG:Going to execute:
assert X2
Level 1: evaluation returns
assert X2; [ exact (id0 id1) | clear id0 ]
where
id1 := H
of type
intropattern
id0 := H0
of type
intropattern
flags := 
of type
tauto_flags
X2 := B
of type
constr of type tacvalue