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| author | Ben Gamari <ben@smart-cactus.org> | 2020-02-06 11:12:04 -0500 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2020-02-08 10:22:45 -0500 |
| commit | bd6667665f160f07550b25e9c80fbc197ae2f642 (patch) | |
| tree | ecb60f9cd3c285347b913ca918fd6d146a5f903c | |
| parent | 3900cb83fb10b0209fb5fb1d713bf3aaf3ee42b8 (diff) | |
| download | haskell-bd6667665f160f07550b25e9c80fbc197ae2f642.tar.gz | |
users-guide: Clarify that bundled patsyns were introduced in GHC 8.0
Closes #17094.
| -rw-r--r-- | docs/users_guide/exts/pattern_synonyms.rst | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/docs/users_guide/exts/pattern_synonyms.rst b/docs/users_guide/exts/pattern_synonyms.rst index fbdd50d083..abb7b82860 100644 --- a/docs/users_guide/exts/pattern_synonyms.rst +++ b/docs/users_guide/exts/pattern_synonyms.rst @@ -298,9 +298,11 @@ example: :: would bring into scope the data constructor ``Just`` from the ``Maybe`` type, without also bringing the type constructor ``Maybe`` into scope. -To bundle a pattern synonym with a type constructor, we list the pattern -synonym in the export list of a module which exports the type constructor. -For example, to bundle ``Zero`` with ``MyNum`` we could write the following: :: +As of GHC 8.0.1 you may also "bundle" pattern synonyms with an exported type +constructor, making that pattern appear as a data constructor of that type. To +bundle a pattern synonym, we list the pattern synonym in the export list of a +module which exports the type constructor. For example, to bundle ``Zero`` +with ``MyNum`` we could write the following: :: module Example ( MyNum(Zero) ) where |