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Diffstat (limited to 'docs/users_guide/using-warnings.rst')
| -rw-r--r-- | docs/users_guide/using-warnings.rst | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/docs/users_guide/using-warnings.rst b/docs/users_guide/using-warnings.rst index 5f07299258..5eb4bc51c9 100644 --- a/docs/users_guide/using-warnings.rst +++ b/docs/users_guide/using-warnings.rst @@ -51,6 +51,7 @@ To reverse ``-Werror``, which makes all warnings into errors, use ``-Wwarn``. * :ghc-flag:`-Wunrecognised-warning-flags` * :ghc-flag:`-Winaccessible-code` * :ghc-flag:`-Wstar-binder` + * :ghc-flag:`-Woperator-whitespace-ext-conflict` The following flags are simple ways to select standard "packages" of warnings: @@ -1853,6 +1854,7 @@ of ``-W(no-)*``. .. ghc-flag:: -Winvalid-haddock :shortdesc: warn when a Haddock comment occurs in an invalid position :type: dynamic + :reverse: -Wno-invalid-haddock :category: :since: 9.0 @@ -1869,6 +1871,56 @@ of ``-W(no-)*``. This warning informs you about discarded documentation comments. It has no effect when :ghc-flag:`-haddock` is disabled. +.. ghc-flag:: -Woperator-whitespace-ext-conflict + :shortdesc: warn on uses of infix operators that would be parsed differently + were a particular GHC extension enabled + :type: dynamic + :reverse: -Wno-operator-whitespace-ext-conflict + :category: + + :since: 9.2 + + When :extension:`TemplateHaskell` is enabled, ``f $x`` is parsed as ``f`` + applied to an untyped splice. But when the extension is disabled, the + expression is parsed as a use of the ``$`` infix operator. + + To make it easy to read ``f $x`` without checking the enabled extensions, + one could rewrite it as ``f $ x``, which is what this warning suggests. + + Currently, it detects the following cases: + + * ``$x`` could mean an untyped splice under :extension:`TemplateHaskell` + * ``$$x`` could mean a typed splice under :extension:`TemplateHaskell` + * ``%m`` could mean a multiplicity annotation under :extension:`LinearTypes` + + It only covers extensions that currently exist. If you want to enforce a + stricter policy and always require whitespace around all infix operators, + use :ghc-flag:`-Woperator-whitespace`. + +.. ghc-flag:: -Woperator-whitespace + :shortdesc: warn on prefix, suffix, and tight infix uses of infix operators + :type: dynamic + :reverse: -Wno-operator-whitespace + :category: + + :since: 9.2 + + There are four types of infix operator occurrences, as defined by + `GHC Proposal #229 <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0229-whitespace-bang-patterns.rst>`__:: + + a ! b -- a loose infix occurrence + a!b -- a tight infix occurrence + a !b -- a prefix occurrence + a! b -- a suffix occurrence + + A loose infix occurrence of any operator is always parsed as an infix + operator, but other occurrence types may be assigned a special meaning. + For example, a prefix ``!`` denotes a bang pattern, and a prefix ``$`` + denotes a :extension:`TemplateHaskell` splice. + + This warning encourages the use of loose infix occurrences of all infix + operators, to prevent possible conflicts with future language extensions. + .. ghc-flag:: -Wauto-orphans :shortdesc: *(deprecated)* Does nothing :type: dynamic |