pub fn add_defer(
  context: DeferContext,
  defer_func: fn() -> Nil,
  first: fn(DeferContext) -> #(DeferContext, a),
) -> #(DeferContext, a)

pub fn defer(
  last defer_func: fn() -> a,
  first rest: fn() -> b,
) -> b

pub fn start_defer(
  defer_func: fn() -> Nil,
  rest: fn(DeferContext) -> #(DeferContext, a),
) -> a