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Diffstat (limited to 'docs/users_guide/8.2.1-notes.rst')
| -rw-r--r-- | docs/users_guide/8.2.1-notes.rst | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/docs/users_guide/8.2.1-notes.rst b/docs/users_guide/8.2.1-notes.rst index 9a222e6003..b3dd2de93e 100644 --- a/docs/users_guide/8.2.1-notes.rst +++ b/docs/users_guide/8.2.1-notes.rst @@ -157,6 +157,16 @@ Compiler - The :ghc-flag:`-XExtendedDefaultRules` extension now defaults multi-parameter typeclasses. See :ghc-ticket:`12923`. +- GHC now ignores ``RULES`` for data constructors (:ghc-ticket:`13290`). + Previously, it accepted:: + + "NotAllowed" forall x. Just x = e + + That rule will no longer take effect, and a warning will be issued. ``RULES`` + may still mention data constructors, but not in the outermost position:: + + "StillWorks" forall x. f (Just x) = e + GHCi ~~~~ |