file: Refactor io_device type

lib/kernel/src/file.erl

@@ -238,7 +238,7 @@ operating system kernel.
 
 %% Types that can be used from other modules -- alphabetically ordered.
 -export_type([date_time/0, fd/0, file_info/0, filename/0, filename_all/0,
-              io_device/0, location/0, mode/0, name/0, name_all/0, posix/0]).
+              io_device/0, io_server/0, location/0, mode/0, name/0, name_all/0, posix/0]).
 
 %%% Includes and defines
 -include("file_int.hrl").
@@ -264,8 +264,14 @@ See the documentation of the `t:name_all/0` type.".
 -type file_descriptor() :: #file_descriptor{}.
 -doc "A file descriptor representing a file opened in [`raw`](`m:file#raw`) mode.".
 -type fd()        :: file_descriptor().
--doc "As returned by `open/2`; `t:pid/0` is a process handling I/O-protocols.".
--type io_device() :: pid() | fd().
+-doc "A process handling the I/O protocol.".
+-type io_server() :: pid().
+-doc """
+An IO device as returned by `open/2`.
+
+`t:io_server/0` is returned by default and `t:fd/0` is returned if the `raw` option is given.
+""".
+-type io_device() :: io_server() | fd().
 -type location()  :: integer() | {'bof', Offset :: integer()}
                    | {'cur', Offset :: integer()}
 		   | {'eof', Offset :: integer()} | 'bof' | 'cur' | 'eof'.

lib/stdlib/src/io.erl

@@ -142,10 +142,10 @@ handled by `user`.
 """.
 -type user() :: user.
 -doc """
-An I/O device, either `standard_io`, `standard_error`, `user`, a registered
-name, or a pid handling I/O protocols (returned from `file:open/2`).
+An I/O device, either `t:standard_io/0`, `t:standard_error/0`, `t:user/0`, a `t:file:io_server/0`,
+a registered name, or any pid handling I/O protocols.
 """.
--type device() :: atom() | pid() | standard_io() | standard_error() | user().
+-type device() :: atom() | pid() | file:io_server() | standard_io() | standard_error() | user().
 -type prompt() :: atom() | unicode:chardata().
 
 %% ErrorDescription is whatever the I/O-server sends.
@@ -494,8 +494,8 @@ The options and values supported by the OTP I/O devices are as follows:
   functions can handle any of these modes and so should other, user-written,
   modules behaving as clients to I/O servers.
 
-  This option is supported by the standard shell (`group.erl`), the 'oldshell'
-  (`user.erl`), and the file I/O servers.
+  This option is supported by the `t:standard_io/0`, `t:user/0` and `t:file:io_server/0`
+   I/O servers.
 
 - **`{echo, boolean()}`** - Denotes if the terminal is to echo input. Only
   supported for the standard shell I/O server (`group.erl`)