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behaviour.ex
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behaviour.ex
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defmodule Behaviour do
@moduledoc """
This module has been deprecated.
Instead of `defcallback`, one can simply use `@callback`.
Instead of `defmacrocallback`, one can simply use `@macrocallback`.
Instead of `__behaviour__(:callbacks)`, one can simply use `behaviour_info(:callbacks)`.
"""
# TODO: Deprecate by 1.2
# TODO: Remove by 2.0
@doc """
Defines a function callback according to the given type specification.
"""
defmacro defcallback(spec) do
do_defcallback(:def, split_spec(spec, quote(do: term)))
end
@doc """
Defines a macro callback according to the given type specification.
"""
defmacro defmacrocallback(spec) do
do_defcallback(:defmacro, split_spec(spec, quote(do: Macro.t)))
end
defp split_spec({:when, _, [{:::, _, [spec, return]}, guard]}, _default) do
{spec, return, guard}
end
defp split_spec({:when, _, [spec, guard]}, default) do
{spec, default, guard}
end
defp split_spec({:::, _, [spec, return]}, _default) do
{spec, return, []}
end
defp split_spec(spec, default) do
{spec, default, []}
end
defp do_defcallback(kind, {spec, return, guards}) do
case Macro.decompose_call(spec) do
{name, args} ->
do_callback(kind, name, args, return, guards)
_ ->
raise ArgumentError, "invalid syntax in #{kind}callback #{Macro.to_string(spec)}"
end
end
defp do_callback(kind, name, args, return, guards) do
:lists.foreach fn
{:::, _, [left, right]} ->
ensure_not_default(left)
ensure_not_default(right)
left
other ->
ensure_not_default(other)
other
end, args
spec =
quote do
unquote(name)(unquote_splicing(args)) :: unquote(return) when unquote(guards)
end
case kind do
:def -> quote(do: @callback unquote(spec))
:defmacro -> quote(do: @macrocallback unquote(spec))
end
end
defp ensure_not_default({:\\, _, [_, _]}) do
raise ArgumentError, "default arguments \\\\ not supported in defcallback/defmacrocallback"
end
defp ensure_not_default(_), do: :ok
@doc false
defmacro __using__(_) do
quote do
@doc false
def __behaviour__(:callbacks) do
__MODULE__.behaviour_info(:callbacks)
end
def __behaviour__(:docs) do
for {tuple, line, kind, docs} <- Code.get_docs(__MODULE__, :callback_docs) do
case kind do
:callback -> {tuple, line, :def, docs}
:macrocallback -> {tuple, line, :defmacro, docs}
end
end
end
import unquote(__MODULE__)
end
end
end