matchFamCmpNat :: [Type] -> Maybe (CoAxiomRule, [Type], Type)
matchFamCmpNat [s,t]
  | Just x <- mbX, Just y <- mbY =
    Just (axCmpNatDef, [s,t], ordering (compare x y))
  | tcEqType s t = Just (axCmpNatRefl, [s], ordering EQ)
  where mbX = isNumLitTy s
        mbY = isNumLitTy t
matchFamCmpNat :: [Type] -> Maybe (CoAxiomRule, [Type], Type)
matchFamCmpNat [s,t]
  | Just x <- mbX, Just y <- mbY =
    Just (axCmpNatDef, [s,t], ordering (compare x y))
  | tcEqType s t = Just (axCmpNatRefl, [s], ordering EQ)
  where mbX = isNumLitTy s
        mbY = isNumLitTy t
matchFamCmpNat [s,t]
  | Just x <- mbX, Just y <- mbY =
    Just (axCmpNatDef, [s,t], ordering (compare x y))
  | tcEqType s t = Just (axCmpNatRefl, [s], ordering EQ)
  where mbX = isNumLitTy s
        mbY = isNumLitTy t