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| author | chessai <chessai1996@gmail.com> | 2018-12-26 12:12:37 -0500 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2019-01-06 07:27:09 -0500 |
| commit | c121e33f9b039acf2ac6939af8bfafe593560039 (patch) | |
| tree | bb61fb561f3fce2c0f5d8d90884e76d5297bc609 /docs | |
| parent | 08b8ea2f4f1bbc1c61a7cca03ae7fa8ffb099556 (diff) | |
| download | haskell-c121e33f9b039acf2ac6939af8bfafe593560039.tar.gz | |
Add -Wmissing-deriving-strategies
Warn users when -XDerivingStrategies is enabled but not used, at each
potential use site.
add -Wmissing-deriving-strategies
Reviewers: bgamari, RyanGlScott
Subscribers: andrewthad, rwbarton, carter
GHC Trac Issues: #15798
Differential Revision: https://phabricator.haskell.org/D5451
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/8.8.1-notes.rst | 4 | ||||
| -rw-r--r-- | docs/users_guide/extending_ghc.rst | 1 | ||||
| -rw-r--r-- | docs/users_guide/using-warnings.rst | 21 |
3 files changed, 26 insertions, 0 deletions
diff --git a/docs/users_guide/8.8.1-notes.rst b/docs/users_guide/8.8.1-notes.rst index 69d539748d..cd4c00d1a4 100644 --- a/docs/users_guide/8.8.1-notes.rst +++ b/docs/users_guide/8.8.1-notes.rst @@ -84,6 +84,10 @@ Compiler - The deprecated ghc-flag ``-Wamp`` has been removed. +- Add new :ghc-flag:`-Wmissing-deriving-strategies` flag that warns users when they are not + taking advantage of :extension:`DerivingStrategies`. The warning is supplied at each + ``deriving`` site. + Runtime system ~~~~~~~~~~~~~~ diff --git a/docs/users_guide/extending_ghc.rst b/docs/users_guide/extending_ghc.rst index a913684a15..02847c9b86 100644 --- a/docs/users_guide/extending_ghc.rst +++ b/docs/users_guide/extending_ghc.rst @@ -851,6 +851,7 @@ In general, the ``pluginRecompile`` field has the following type:: The ``PluginRecompile`` data type is an enumeration determining how the plugin should affect recompilation. :: + data PluginRecompile = ForceRecompile | NoForceRecompile | MaybeRecompile Fingerprint A plugin which declares itself impure using ``ForceRecompile`` will always diff --git a/docs/users_guide/using-warnings.rst b/docs/users_guide/using-warnings.rst index 6a6166bf0d..03ca184531 100644 --- a/docs/users_guide/using-warnings.rst +++ b/docs/users_guide/using-warnings.rst @@ -904,6 +904,27 @@ of ``-W(no-)*``. This option isn't enabled by default because it can be very noisy, and it often doesn't indicate a bug in the program. +.. ghc-flag:: -Wmissing-deriving-strategies + :shortdesc: warn when a deriving clause is missing a deriving strategy + :type: dynamic + :reverse: -Wno-missing-deriving-strategies + :category: + + :since: 8.8.1 + + The datatype below derives the ``Eq`` typeclass, but doesn't specify a + strategy. When :ghc-flag:`-Wmissing-deriving-strategies` is enabled, + the compiler will emit a warning about this. :: + + data Foo a = Foo a + deriving (Eq) + + The compiler will warn here that the deriving clause doesn't specify a + strategy. If the warning is enabled, but :extension:`DerivingStrategies` is + not enabled, the compiler will suggest turning on the + :extension:`DerivingStrategies` extension. This option is not on by default, + having to be turned on manually or with :ghc-flag:`-Weverything`. + .. ghc-flag:: -Wmissing-fields :shortdesc: warn when fields of a record are uninitialised :type: dynamic |