CMP0121
-------

.. versionadded:: 3.21

The :command:`list` command now detects invalid indices.

Prior to CMake version 3.21, the :command:`list` command's ``GET``,
``INSERT``, ``SUBLIST``, and ``REMOVE_AT`` subcommands did not detect invalid
index arguments.

The ``OLD`` behavior of this policy is for invalid indices to be treated as
their integer value (if any) at the start of the string. For example,
``2good4you`` is a ``2`` and ``not_an_integer`` is a ``0``. The ``NEW``
behavior is for invalid indices to trigger an error.

.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 3.21
.. |WARNS_OR_DOES_NOT_WARN| replace:: warns
.. include:: include/STANDARD_ADVICE.rst

.. include:: include/DEPRECATED.rst
