@type pure() ::
  :u1
  | :u2
  | :u4
  | :u8
  | :s1
  | :s2
  | :s4
  | :s8
  | {:bits, non_neg_integer()}
  | :f4
  | :f8
  | :bytes
  | :str
  | :bool
  | :struct
  | :io
  | :any
  | {:user_defined, String.t()}

@type type_ref() ::
  pure()
  | :u2le
  | :u2be
  | :u4le
  | :u4be
  | :u8le
  | :u8be
  | :s2le
  | :s2be
  | :s4le
  | :s4be
  | :s8le
  | :s8be
  | :f4le
  | :f4be
  | :f8le
  | :f8be
  | :strz