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| author | Ryan Scott <ryan.gl.scott@gmail.com> | 2016-12-01 12:24:48 -0500 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2016-12-01 12:24:48 -0500 |
| commit | a452c6e57a286f3b31f0e3fbef83cbea0cee8b34 (patch) | |
| tree | 76da037341de361bbd6bb90d7b48987c2aa1f19d | |
| parent | 514c01eec5f2b23f278c29b61345dce6c37900f1 (diff) | |
| download | haskell-a452c6e57a286f3b31f0e3fbef83cbea0cee8b34.tar.gz | |
Make note of #12907 in 8.0.2 release notes
Test Plan: Read it, commit it, merge it, ship it
Reviewers: goldfire, bgamari, austin, hvr, simonpj
Reviewed By: simonpj
Subscribers: thomie
Differential Revision: https://phabricator.haskell.org/D2774
GHC Trac Issues: #12907
| -rw-r--r-- | docs/users_guide/8.0.2-notes.rst | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/docs/users_guide/8.0.2-notes.rst b/docs/users_guide/8.0.2-notes.rst index 9bc78ea224..fa7aa8db3d 100644 --- a/docs/users_guide/8.0.2-notes.rst +++ b/docs/users_guide/8.0.2-notes.rst @@ -86,6 +86,19 @@ Language instance {-# OVERLAPPING #-} Foo Int +- GHC now adheres more closely to the Haskell 2010 Report with respect to + defaulting rules. As a result, GHC will now reject some defaulting rules + which GHC 8.0.1 and earlier would accept. For example, this is now + rejected :: + + module Foo where + default (Bool) + + because when the :ghc-flag:`-XExtendedDefaultRules` extension is not + enabled, defaulting rules only work for the ``Num`` class, of which ``Bool`` + is not an instance. To make GHC accept the above program, simply enable the + :ghc-flag:`-XExtendedDefaultRules` extension. + Compiler ~~~~~~~~ |