Goal:
  
  b : Byte.byte
  xs : t
  b0 : Byte.byte
  ys : t
  IHxs : forall ys : t,
         eqb xs ys = match compare xs ys with
                     | Eq => true
                     | _ => false
                     end
  ============================
   ((if ByteCompare.eqb b b0 then eqb xs ys else false) =
    match
      match ByteCompare.compare b b0 with
      | Eq => compare xs ys
      | Lt => Lt
      | Gt => Gt
      end
    with
    | Eq => true
    | _ => false
    end)


DEBUG:Going to execute:
case not_locked_false_eq_true; Ltac.assumption
Level 1: Backtrace:

In environment
b : Byte.byte
xs : t
b0 : Byte.byte
ys : t
IHxs : forall ys : t,
       eqb xs ys = match compare xs ys with
                   | Eq => true
                   | _ => false
                   end
Unable to unify
 "match
    match ByteCompare.compare b b0 with
    | Eq => compare xs ys
    | Lt => Lt
    | Gt => Gt
    end
  with
  | Eq => true
  | _ => false
  end"
with "if ByteCompare.eqb b b0 then eqb xs ys else false".
Level 0: Backtrace:

In environment
b : Byte.byte
xs : t
b0 : Byte.byte
ys : t
IHxs : forall ys : t,
       eqb xs ys = match compare xs ys with
                   | Eq => true
                   | _ => false
                   end
Unable to unify
 "match
    match ByteCompare.compare b b0 with
    | Eq => compare xs ys
    | Lt => Lt
    | Gt => Gt
    end
  with
  | Eq => true
  | _ => false
  end"
with "if ByteCompare.eqb b b0 then eqb xs ys else false".
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.