Goal:
  
  b : Byte.byte
  y : string
  H : match ByteCompare.compare b b with
      | Eq => compare y y
      | Lt => Lt
      | Gt => Gt
      end = Lt
  IHy : compare y y = Lt -> False
  ============================
   False


DEBUG:Going to execute:
<coq-core.plugins.ssreflect::ssrrewrite@0> $1 $2
Level 0: Backtrace:

Tactic failure: congruence failed.
Level 0: Backtrace:

Tactic failure: congruence failed.