#15694: Link discussion of file objects to glossary entry.

This is analogous to the link for `flie objects` in the description of
'open' that exists in the 2.7 docs, and adds a similar link to the
io docs.

Patch by Chris Jerdonek.

Doc/library/functions.rst

@@ -790,10 +790,13 @@ are always available.  They are listed here in alphabetical order.
    :meth:`__index__` method that returns an integer.
 
 
+   .. index::
+      single: file object; open() built-in function
+
 .. function:: open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True)
 
-   Open *file* and return a corresponding stream.  If the file cannot be opened,
-   an :exc:`IOError` is raised.
+   Open *file* and return a corresponding :term:`file object`.  If the file
+   cannot be opened, an :exc:`IOError` is raised.
 
    *file* is either a string or bytes object giving the pathname (absolute or
    relative to the current working directory) of the file to be opened or
@@ -900,7 +903,8 @@ are always available.  They are listed here in alphabetical order.
    closed.  If a filename is given *closefd* has no effect and must be ``True``
    (the default).
 
-   The type of file object returned by the :func:`open` function depends on the
+   The type of :term:`file object` returned by the :func:`open` function
+   depends on the
    mode.  When :func:`open` is used to open a file in a text mode (``'w'``,
    ``'r'``, ``'wt'``, ``'rt'``, etc.), it returns a subclass of
    :class:`io.TextIOBase` (specifically :class:`io.TextIOWrapper`).  When used

Doc/library/io.rst

@@ -16,11 +16,15 @@
 Overview
 --------
 
-The :mod:`io` module provides Python's main facilities for dealing for various
-types of I/O.  There are three main types of I/O: *text I/O*, *binary I/O*, *raw
-I/O*.  These are generic categories, and various backing stores can be used for
-each of them.  Concrete objects belonging to any of these categories will often
-be called *streams*; another common term is *file-like objects*.
+.. index::
+   single: file object; io module
+
+The :mod:`io` module provides Python's main facilities for dealing with various
+types of I/O.  There are three main types of I/O: *text I/O*, *binary I/O*
+and *raw I/O*.  These are generic categories, and various backing stores can
+be used for each of them.  A concrete object belonging to any of these
+categories is called a :term:`file object`.  Other common terms are *stream*
+and *file-like object*.
 
 Independently of its category, each concrete stream object will also have
 various capabilities: it can be read-only, write-only, or read-write. It can