Goal:
    A : Type  R : ReflectEq A  x : A  y : A  Heq_anonymous : true = (x == y)
  ============================
   (x = y)


DEBUG:Going to execute:
Tactics.destruct_one_ex
Level 1: Backtrace:

No matching clauses for match.
Level 0: Backtrace:

No matching clauses for match.