∀ {motive : Lean.Grind.CommRing.Expr → Sort u} (t : Lean.Grind.CommRing.Expr)
  (num : (k : ℤ) → motive (Lean.Grind.CommRing.Expr.num k))
  (var : (i : Lean.Grind.CommRing.Var) → motive (Lean.Grind.CommRing.Expr.var i))
  («else» : Nat.hasNotBit 9 t.ctorIdx → motive t) (h : Nat.hasNotBit 9 t.ctorIdx),
  Lean.Grind.CommRing.Expr.toPolyS._sparseCasesOn_1 t num var «else» = «else» h