diff options
| author | HE, Tao <sighingnow@gmail.com> | 2018-02-12 19:55:41 -0500 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2018-02-13 17:49:43 -0500 |
| commit | 8936ab69d18669bab3ca4edf40458f88ae5903f0 (patch) | |
| tree | f793c1a8f115a0956386a78f355d30836805272e /docs | |
| parent | 0c9777b787d072f9f57e0cdfe44e2e2d48217077 (diff) | |
| download | haskell-8936ab69d18669bab3ca4edf40458f88ae5903f0.tar.gz | |
Raise parse error for `data T where`.
Empty GADTs data declarations can't be identified in type checker. This
patch adds additional checks in parser and raise a parse error when
encounter empty GADTs declarations but extension `GADTs` is not enabled.
Only empty declarations are checked in parser to avoid affecting
existing
error messages related to missing GADTs extension.
This patch should fix issue 8258.
Signed-off-by: HE, Tao <sighingnow@gmail.com>
Test Plan: make test TEST="T8258 T8258NoGADTs"
Reviewers: bgamari, mpickering, alanz, RyanGlScott
Reviewed By: bgamari, RyanGlScott
Subscribers: adamse, RyanGlScott, rwbarton, thomie, mpickering, carter
GHC Trac Issues: #8258
Differential Revision: https://phabricator.haskell.org/D4350
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/8.6.1-notes.rst | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/docs/users_guide/8.6.1-notes.rst b/docs/users_guide/8.6.1-notes.rst index e844ab6b2a..8f7e961b4f 100644 --- a/docs/users_guide/8.6.1-notes.rst +++ b/docs/users_guide/8.6.1-notes.rst @@ -22,6 +22,14 @@ Full details Language ~~~~~~~~ +- Data declarations with empty ``where`` clauses are no longer valid without the + extension :extension:`GADTSyntax` enabled. For instance, consider the + following, :: + + data T where + + The grammar is invalid in Haskell2010. Previously it could be compiled successfully + without ``GADTs``. As of GHC 8.6.1, this is a parse error. Compiler ~~~~~~~~ |