Goal:
    x : t  y : t  Heq_anonymous : true = eqb x y
  ============================
   (x = y)


DEBUG:Going to execute:
subst *
Level 0: Backtrace:

Failed to progress.
Level 1: Backtrace:

Failed to progress.
Level 0: Backtrace:

Failed to progress.
Level 0: Backtrace:

Failed to progress.