[Compiler.saveMono] size: 17
    def sefFn e f : Expr :=
      cases e : Expr
      | Lean.Expr.app._impl data fn.1 arg.2 =>
        jp _jp.3 _y.4 : Expr :=
          cases _y.4 : Expr
          | Bool.false =>
            let _x.5 := Expr.app._override f arg.2;
            return _x.5
          | Bool.true =>
            return e;
        let _x.6 := ptrAddrUnsafe ◾ fn.1;
        let _x.7 := ptrAddrUnsafe ◾ f;
        let _x.8 := USize.decEq _x.6 _x.7;
        cases _x.8 : Expr
        | Bool.false =>
          goto _jp.3 _x.8
        | Bool.true =>
          let _x.9 := ptrAddrUnsafe ◾ arg.2;
          let _x.10 := USize.decEq _x.9 _x.9;
          goto _jp.3 _x.10
      | _ =>
        return e