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Diffstat (limited to 'docs/users_guide/using-warnings.rst')
| -rw-r--r-- | docs/users_guide/using-warnings.rst | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/docs/users_guide/using-warnings.rst b/docs/users_guide/using-warnings.rst index 2c70006a7c..3624a63384 100644 --- a/docs/users_guide/using-warnings.rst +++ b/docs/users_guide/using-warnings.rst @@ -2319,6 +2319,22 @@ of ``-W(no-)*``. triggered whenever this happens, and can be addressed by enabling the extension. +.. ghc-flag:: -Wloopy-superclass-solve + :shortdesc: warn when creating potentially-loopy superclass constraint evidence + :type: dynamic + :reverse: -Wno-loopy-superclass-solve + + :since: 9.6.1 + + As explained in :ref:`undecidable_instances`, when using + :extension:`UndecidableInstances` it is possible for GHC to construct + non-terminating evidence for certain superclass constraints. + + This behaviour is scheduled to be removed in a future GHC version. + In the meantime, GHC emits this warning to inform users of potential + non-termination. Users can manually add the required constraint to the context + to avoid the problem (thus silencing the warning). + .. ghc-flag:: -Wterm-variable-capture :shortdesc: warn when an implicitly quantified type variable captures a term's name :type: dynamic |