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Diffstat (limited to 'docs/users_guide/exts/monadfail_desugaring.rst')
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diff --git a/docs/users_guide/exts/monadfail_desugaring.rst b/docs/users_guide/exts/monadfail_desugaring.rst new file mode 100644 index 0000000000..ddc6cff6b4 --- /dev/null +++ b/docs/users_guide/exts/monadfail_desugaring.rst @@ -0,0 +1,23 @@ +.. _monadfail-desugaring: + +New monadic failure desugaring mechanism +---------------------------------------- + +.. extension:: MonadFailDesugaring + :shortdesc: Enable monadfail desugaring. + + :since: 8.0.1 + + Use the ``MonadFail.fail`` instead of the legacy ``Monad.fail`` function + when desugaring refutable patterns in ``do`` blocks. + +The ``-XMonadFailDesugaring`` extension switches the desugaring of +``do``-blocks to use ``MonadFail.fail`` instead of ``Monad.fail``. + +This extension is enabled by default since GHC 8.6.1, under the +`MonadFail Proposal (MFP) +<https://prime.haskell.org/wiki/Libraries/Proposals/MonadFail>`__. + +This extension is temporary, and will be deprecated in a future release. + + |