[init]
def sefFn (x_1 : obj) (x_2 : obj) : obj :=
  case x_1 : obj of
  Lean.Expr.bvar._impl →
    ret x_1
  Lean.Expr.fvar._impl →
    ret x_1
  Lean.Expr.mvar._impl →
    ret x_1
  Lean.Expr.sort._impl →
    ret x_1
  Lean.Expr.const._impl →
    ret x_1
  Lean.Expr.app._impl →
    let x_3 : obj := proj[1] x_1;
    let x_4 : obj := Lean.Expr.updateApp x_1 x_2 x_3 ◾;
    ret x_4
  Lean.Expr.lam._impl →
    ret x_1
  Lean.Expr.forallE._impl →
    ret x_1
  Lean.Expr.letE._impl →
    ret x_1
  Lean.Expr.lit._impl →
    ret x_1
  Lean.Expr.mdata._impl →
    ret x_1
  Lean.Expr.proj._impl →
    ret x_1