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Diffstat (limited to 'docs/users_guide/8.10.1-notes.rst')
| -rw-r--r-- | docs/users_guide/8.10.1-notes.rst | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/docs/users_guide/8.10.1-notes.rst b/docs/users_guide/8.10.1-notes.rst index 2ca9ce5c08..e8316d7059 100644 --- a/docs/users_guide/8.10.1-notes.rst +++ b/docs/users_guide/8.10.1-notes.rst @@ -90,6 +90,16 @@ Language for a ``newtype``. This was proposed in `GHC proposal #13 <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0013-unlifted-newtypes.rst>`__. +- New flag :ghc-flag:`-Wderiving-defaults` that controls a warning + message when both :extension:`DeriveAnyClass` and + :extension:`GeneralizedNewtypeDeriving` are enabled and no explicit + deriving strategy is in use. The warning is enabled by default and + has been present in earlier GHC versions but without the option of + disabling it. For example, this code would trigger the warning: :: + + class C a + newtype T a = MkT a deriving C + Compiler ~~~~~~~~ |