diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/8.8.1-notes.rst | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/docs/users_guide/8.8.1-notes.rst b/docs/users_guide/8.8.1-notes.rst index f97e79a3cf..0a095f02f2 100644 --- a/docs/users_guide/8.8.1-notes.rst +++ b/docs/users_guide/8.8.1-notes.rst @@ -27,6 +27,19 @@ Language they could only stand in for other type variables, but this restriction was deemed unnecessary in `GHC proposal #29 <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0029-scoped-type-variables-types.rst>`__. Also see :ghc-ticket:`15050`. +- The pattern-match coverage checker now checks for cases that are unreachable + due to constructors have strict argument types. For instance, in the + following example: :: + + data K = K1 | K2 !Void + + f :: K -> () + f K1 = () + + ``K2`` cannot be matched on in ``f``, since it is impossible to construct a + terminating value of type ``Void``. Accordingly, GHC will not warn about + ``K2`` (whereas previous versions of GHC would). + Compiler ~~~~~~~~ |