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Diffstat (limited to 'docs/users_guide/using-warnings.rst')
| -rw-r--r-- | docs/users_guide/using-warnings.rst | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/docs/users_guide/using-warnings.rst b/docs/users_guide/using-warnings.rst index 577bce0a74..922a9638c0 100644 --- a/docs/users_guide/using-warnings.rst +++ b/docs/users_guide/using-warnings.rst @@ -2393,6 +2393,28 @@ of ``-W(no-)*``. When :ghc-flag:`-Wterm-variable-capture` is enabled, GHC warns against implicit quantification that would stop working under ``RequiredTypeArguments``. +.. ghc-flag:: -Wmissing-role-annotations + :shortdesc: warn when type declarations don't have role annotations + :type: dynamic + :reverse: -Wno-role-annotations-signatures + :category: + + :since: 9.8 + :default: off + + .. index:: + single: roles, missing + + If you would like GHC to check that every data type definition + has a :ref:`role annotation <role-annotations>`, use the + :ghc-flag:`-Wmissing-role-annotations` option. + You can specify the role via :extension:`RoleAnnotations`. + + GHC will not warn about type class definitions with missing role annotations, + as their default roles are the strictest: all nominal. + In other words the type-class role cannot be accidentally left + representational or phantom, which could affected the code correctness. + If you're feeling really paranoid, the :ghc-flag:`-dcore-lint` option is a good choice. It turns on heavyweight intra-pass sanity-checking within GHC. (It checks GHC's |