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| author | Ben Gamari <ben@smart-cactus.org> | 2016-03-29 16:30:29 +0200 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2016-03-29 18:58:39 +0200 |
| commit | ae6a56ee467d675776be75dc982f5efb2135d3d4 (patch) | |
| tree | 837ed4937801709bc2b1cf75fd7fe1dffd56cce4 /docs | |
| parent | d5d6804d37960ece2652196f3661604a70c12ffc (diff) | |
| download | haskell-ae6a56ee467d675776be75dc982f5efb2135d3d4.tar.gz | |
users-guide/rel-notes: Note broken-ness of ImpredicativeTypes
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/8.0.1-notes.rst | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/docs/users_guide/8.0.1-notes.rst b/docs/users_guide/8.0.1-notes.rst index 2ebba6e1e6..fe77bf42c0 100644 --- a/docs/users_guide/8.0.1-notes.rst +++ b/docs/users_guide/8.0.1-notes.rst @@ -205,6 +205,14 @@ Language result, :ghc-flag:`-XDeriveTraversable` now works on datatypes that contain arguments which have unlifted types. +- Note that the :ghc-flag:`-XImpredicativeTypes` extension, which has been + :ghc-wiki:`known <ImpredicativePolymorphism>` to be broken for many years, is even more + broken than usual in this release (see :ghc-ticket:`11319`, + :ghc-ticket:`11675`, and others). During pre-release testing we encountered + a number of projects that broke with confusing type errors due to (often + unnecessary) use of :ghc-flag:`-XImpredicativeTypes`. Users of + :ghc-flag:`-XImpredicativeTypes` do so at their own risk! + Compiler ~~~~~~~~ |