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Diffstat (limited to 'docs/users_guide/using-warnings.rst')
| -rw-r--r-- | docs/users_guide/using-warnings.rst | 432 |
1 files changed, 408 insertions, 24 deletions
diff --git a/docs/users_guide/using-warnings.rst b/docs/users_guide/using-warnings.rst index 48a9296b1a..39d7de4147 100644 --- a/docs/users_guide/using-warnings.rst +++ b/docs/users_guide/using-warnings.rst @@ -37,6 +37,10 @@ generally likely to indicate bugs in your program. These are: The following flags are simple ways to select standard "packages" of warnings: .. ghc-flag:: -W + :shortdesc: enable normal warnings + :type: dynamic + :reverse: -w + :category: Provides the standard warnings plus @@ -53,6 +57,10 @@ The following flags are simple ways to select standard "packages" of warnings: * :ghc-flag:`-Wunbanged-strict-patterns` .. ghc-flag:: -Wall + :shortdesc: enable almost all warnings (details in :ref:`options-sanity`) + :type: dynamic + :reverse: -w + :category: Turns on all warning options that indicate potentially suspicious code. The warnings that are *not* enabled by :ghc-flag:`-Wall` are @@ -72,6 +80,11 @@ The following flags are simple ways to select standard "packages" of warnings: * :ghc-flag:`-Wredundant-constraints` .. ghc-flag:: -Wcompat + :shortdesc: enable future compatibility warnings + (details in :ref:`options-sanity`) + :type: dynamic + :reverse: -Wno-compat + :category: Turns on warnings that will be enabled by default in the future, but remain off in normal compilations for the time being. This allows library authors @@ -88,10 +101,17 @@ The following flags are simple ways to select standard "packages" of warnings: * :ghc-flag:`-Wnoncanonical-monoid-instances` .. ghc-flag:: -Wno-compat + :shortdesc: Disables all warnings enabled by :ghc-flag:`-Wcompat`. + :type: dynamic + :reverse: -Wcompat + :category: Disables all warnings enabled by :ghc-flag:`-Wcompat`. .. ghc-flag:: -w + :shortdesc: disable all warnings + :type: dynamic + :category: Turns off all warnings, including the standard ones and those that :ghc-flag:`-Wall` doesn't enable. @@ -100,11 +120,19 @@ These options control which warnings are considered fatal and cause compilation to abort. .. ghc-flag:: -Werror + :shortdesc: make warnings fatal + :type: dynamic + :reverse: -Wwarn + :category: Makes any warning into a fatal error. Useful so that you don't miss warnings when doing batch compilation. .. ghc-flag:: -Werror=⟨wflag⟩ + :shortdesc: make a specific warning fatal + :type: dynamic + :reverse: -Wwarn=⟨wflag⟩ + :category: :noindex: :implies: ``-W<wflag>`` @@ -113,11 +141,19 @@ to abort. it hasn't been enabled yet. .. ghc-flag:: -Wwarn + :shortdesc: make warnings non-fatal + :type: dynamic + :reverse: -Werror + :category: Warnings are treated only as warnings, not as errors. This is the default, but can be useful to negate a :ghc-flag:`-Werror` flag. .. ghc-flag:: -Wwarn=⟨wflag⟩ + :shortdesc: make a specific warning non-fatal + :type: dynamic + :reverse: -Werror=⟨wflag⟩ + :category: :noindex: Causes a specific warning to be treated as normal warning, not fatal error. @@ -129,6 +165,10 @@ When a warning is emitted, the specific warning flag which controls it is shown. .. ghc-flag:: -fshow-warning-groups + :shortdesc: show which group an emitted warning belongs to. + :type: dynamic + :reverse: -fno-show-warning-groups + :category: When showing which flag controls a warning, also show the respective warning group flag(s) that warning is contained in. @@ -142,6 +182,11 @@ all these warnings can still be controlled with ``-f(no-)warn-*`` instead of ``-W(no-)*``. .. ghc-flag:: -Wunrecognised-warning-flags + :shortdesc: throw a warning when an unreconised ``-W...`` flag is + encountered on the command line. + :type: dynamic + :reverse: -Wno-unrecognised-warning-flags + :category: Enables warnings when the compiler encounters a ``-W...`` flag that is not recognised. @@ -149,6 +194,12 @@ of ``-W(no-)*``. This warning is on by default. .. ghc-flag:: -Wtyped-holes + :shortdesc: Report warnings when :ref:`typed hole <typed-holes>` errors are + :ref:`deferred until runtime <defer-type-errors>`. See + :ghc-flag:`-fdefer-typed-holes`. + :type: dynamic + :reverse: -Wno-typed-holes + :category: Determines whether the compiler reports typed holes warnings. Has no effect unless typed holes errors are deferred until runtime. See @@ -156,7 +207,13 @@ of ``-W(no-)*``. This warning is on by default. -.. ghc-flag:: -Wtype-errors +.. ghc-flag:: -Wdeferred-type-errors + :shortdesc: Report warnings when :ref:`deferred type errors + <defer-type-errors>` are enabled. This option is enabled by + default. See :ghc-flag:`-fdefer-type-errors`. + :type: dynamic + :reverse: -Wno-deferred-type-errors + :category: Causes a warning to be reported when a type error is deferred until runtime. See :ref:`defer-type-errors` @@ -164,6 +221,14 @@ of ``-W(no-)*``. This warning is on by default. .. ghc-flag:: -fdefer-type-errors + :shortdesc: Turn type errors into warnings, :ref:`deferring the error until + runtime <defer-type-errors>`. Implies + :ghc-flag:`-fdefer-typed-holes` and + :ghc-flag:`-fdefer-out-of-scope-variables`. + See also :ghc-flag:`-Wdeferred-type-errors` + :type: dynamic + :reverse: -fno-defer-type-errors + :category: :implies: :ghc-flag:`-fdefer-typed-holes` @@ -174,6 +239,13 @@ of ``-W(no-)*``. :ref:`defer-type-errors` .. ghc-flag:: -fdefer-typed-holes + :shortdesc: Convert :ref:`typed hole <typed-holes>` errors into warnings, + :ref:`deferring the error until runtime <defer-type-errors>`. + Implied by :ghc-flag:`-fdefer-type-errors`. + See also :ghc-flag:`-Wtyped-holes`. + :type: dynamic + :reverse: -fno-defer-typed-holes + :category: Defer typed holes errors (errors about names with a leading underscore (e.g., “_”, “_foo”, “_bar”)) until runtime. This will turn the errors @@ -185,6 +257,12 @@ of ``-W(no-)*``. Implied by :ghc-flag:`-fdefer-type-errors`. See also :ghc-flag:`-Wtyped-holes`. .. ghc-flag:: -fdefer-out-of-scope-variables + :shortdesc: Convert variable out of scope variables errors into warnings. + Implied by :ghc-flag:`-fdefer-type-errors`. + See also :ghc-flag:`-Wdeferred-out-of-scope-variables`. + :type: dynamic + :reverse: -fno-defer-out-of-scope-variables + :category: Defer variable out-of-scope errors (errors about names without a leading underscore) until runtime. This will turn variable-out-of-scope errors into warnings. @@ -195,10 +273,24 @@ of ``-W(no-)*``. Implied by :ghc-flag:`-fdefer-type-errors`. See also :ghc-flag:`-Wdeferred-out-of-scope-variables`. .. ghc-flag:: -Wdeferred-out-of-scope-variables + :shortdesc: Report warnings when variable out-of-scope errors are + :ref:`deferred until runtime. + See :ghc-flag:`-fdefer-out-of-scope-variables`. + :type: dynamic + :reverse: -Wno-deferred-out-of-scope-variables + :category: Warn when a deferred out-of-scope variable is encountered. .. ghc-flag:: -Wpartial-type-signatures + :shortdesc: warn about holes in partial type signatures when + :ghc-flag:`-XPartialTypeSignatures` is enabled. Not applicable when + :ghc-flag:`-XPartialTypesignatures` is not enabled, in which case + errors are generated for such holes. See + :ref:`partial-type-signatures`. + :type: dynamic + :reverse: -Wno-partial-type-signatures + :category: Determines whether the compiler reports holes in partial type signatures as warnings. Has no effect unless @@ -209,6 +301,10 @@ of ``-W(no-)*``. This warning is on by default. .. ghc-flag:: -fhelpful-errors + :shortdesc: Make suggestions for mis-spelled names. + :type: dynamic + :reverse: -fno-helpful-errors + :category: When a name or package is not found in scope, make suggestions for the name or package you might have meant instead. @@ -216,6 +312,10 @@ of ``-W(no-)*``. This option is on by default. .. ghc-flag:: -Wunrecognised-pragmas + :shortdesc: warn about uses of pragmas that GHC doesn't recognise + :type: dynamic + :reverse: -Wno-unrecognised-pragmas + :category: Causes a warning to be emitted when a pragma that GHC doesn't recognise is used. As well as pragmas that GHC itself uses, GHC also @@ -225,22 +325,47 @@ of ``-W(no-)*``. This option is on by default. .. ghc-flag:: -Wmissed-specialisations - -Wall-missed-specialisations + :shortdesc: warn when specialisation of an imported, overloaded function + fails. + :type: dynamic + :reverse: -Wno-missed-specialisations + :category: Emits a warning if GHC cannot specialise an overloaded function, usually - because the function needs an ``INLINABLE`` pragma. The "all" form reports - all such situations whereas the "non-all" form only reports when the + because the function needs an ``INLINABLE`` pragma. Reports when the situation arises during specialisation of an imported function. - The "non-all" form is intended to catch cases where an imported function - that is marked as ``INLINABLE`` (presumably to enable specialisation) cannot - be specialised as it calls other functions that are themselves not specialised. + This form is intended to catch cases where an imported function + that is marked as ``INLINABLE`` (presumably to enable specialisation) + cannot be specialised as it calls other functions that are themselves not + specialised. - Note that these warnings will not throw errors if used with :ghc-flag:`-Werror`. + Note that this warning will not throw errors if used with + :ghc-flag:`-Werror`. - These options are both off by default. + This option is off by default. + +.. ghc-flag:: -Wall-missed-specialisations + :shortdesc: warn when specialisation of any overloaded function fails. + :type: dynamic + :reverse: -Wno-all-missed-specialisations + :category: + + Emits a warning if GHC cannot specialise an overloaded function, usually + because the function needs an ``INLINABLE`` pragma. Reports + all such situations. + + Note that this warning will not throw errors if used with + :ghc-flag:`-Werror`. + + This option is off by default. .. ghc-flag:: -Wwarnings-deprecations + :shortdesc: warn about uses of functions & types that have warnings or + deprecated pragmas + :type: dynamic + :reverse: -Wno-warnings-deprecations + :category: .. index:: pair: deprecations; warnings @@ -252,6 +377,11 @@ of ``-W(no-)*``. This option is on by default. .. ghc-flag:: -Wdeprecations + :shortdesc: warn about uses of functions & types that have warnings or + deprecated pragmas. Alias for :ghc-flag:`-Wwarnings-deprecations` + :type: dynamic + :reverse: -Wno-deprecations + :category: .. index:: single: deprecations @@ -264,6 +394,11 @@ of ``-W(no-)*``. This option is on by default. .. ghc-flag:: -Wamp + :shortdesc: *(deprecated)* warn on definitions conflicting with the + Applicative-Monad Proposal (AMP) + :type: dynamic + :reverse: -Wno-amp + :category: .. index:: single: AMP @@ -275,6 +410,13 @@ of ``-W(no-)*``. the AMP (Applicative-Monad proosal). .. ghc-flag:: -Wnoncanonical-monad-instances + :shortdesc: warn when ``Applicative`` or ``Monad`` instances have + noncanonical definitions of ``return``, ``pure``, ``(>>)``, + or ``(*>)``. + See flag description in :ref:`options-sanity` for more details. + :type: dynamic + :reverse: -Wno-noncanonical-monad-instances + :category: Warn if noncanonical ``Applicative`` or ``Monad`` instances declarations are detected. @@ -295,6 +437,12 @@ of ``-W(no-)*``. This option is off by default. .. ghc-flag:: -Wnoncanonical-monadfail-instances + :shortdesc: warn when ``Monad`` or ``MonadFail`` instances have + noncanonical definitions of ``fail``. + See flag description in :ref:`options-sanity` for more details. + :type: dynamic + :reverse: -Wno-noncanonical-monadfail-instances + :category: Warn if noncanonical ``Monad`` or ``MonadFail`` instances declarations are detected. @@ -317,6 +465,12 @@ of ``-W(no-)*``. This option is off by default. .. ghc-flag:: -Wnoncanonical-monoid-instances + :shortdesc: warn when ``Semigroup`` or ``Monoid`` instances have + noncanonical definitions of ``(<>)`` or ``mappend``. + See flag description in :ref:`options-sanity` for more details. + :type: dynamic + :reverse: -Wno-noncanonical-monoid-instances + :category: Warn if noncanonical ``Semigroup`` or ``Monoid`` instances declarations are detected. @@ -337,6 +491,11 @@ of ``-W(no-)*``. :ghc-flag:`-Wcompat` option group. .. ghc-flag:: -Wmissing-monadfail-instances + :shortdesc: Warn when a failable pattern is used in a do-block that does + not have a ``MonadFail`` instance. + :type: dynamic + :reverse: -Wno-missing-monadfail-instances + :category: .. index:: single: MFP @@ -353,6 +512,11 @@ of ``-W(no-)*``. <https://prime.haskell.org/wiki/Libraries/Proposals/MonadFail>`__. .. ghc-flag:: -Wsemigroup + :shortdesc: warn when a ``Monoid`` is not ``Semigroup``, and on non- + ``Semigroup`` definitions of ``(<>)``? + :type: dynamic + :reverse: -Wno-semigroup + :category: .. index:: single: semigroup; warning @@ -368,6 +532,10 @@ of ``-W(no-)*``. default, but will be switched on in a future GHC release. .. ghc-flag:: -Wdeprecated-flags + :shortdesc: warn about uses of commandline flags that are deprecated + :type: dynamic + :reverse: -Wno-deprecated-flags + :category: .. index:: single: deprecated flags @@ -378,6 +546,10 @@ of ``-W(no-)*``. This option is on by default. .. ghc-flag:: -Wunsupported-calling-conventions + :shortdesc: warn about use of an unsupported calling convention + :type: dynamic + :reverse: -Wno-unsupported-calling-conventions + :category: Causes a warning to be emitted for foreign declarations that use unsupported calling conventions. In particular, if the ``stdcall`` @@ -385,6 +557,10 @@ of ``-W(no-)*``. it will be treated as ``ccall``. .. ghc-flag:: -Wdodgy-foreign-imports + :shortdesc: warn about dodgy foreign imports + :type: dynamic + :reverse: -Wno-dodgy-foreign-import + :category: Causes a warning to be emitted for foreign imports of the following form: :: @@ -403,6 +579,10 @@ of ``-W(no-)*``. warning. .. ghc-flag:: -Wdodgy-exports + :shortdesc: warn about dodgy exports + :type: dynamic + :reverse: -Wno-dodgy-exports + :category: Causes a warning to be emitted when a datatype ``T`` is exported with all constructors, i.e. ``T(..)``, but is it just a type @@ -412,6 +592,10 @@ of ``-W(no-)*``. but that module exports nothing. .. ghc-flag:: -Wdodgy-imports + :shortdesc: warn about dodgy imports + :type: dynamic + :reverse: -Wno-dodgy-imports + :category: Causes a warning to be emitted in the following cases: @@ -422,16 +606,28 @@ of ``-W(no-)*``. exported. .. ghc-flag:: -Woverflowed-literals + :shortdesc: warn about literals that will overflow their type + :type: dynamic + :reverse: -Wno-overflowed-literals + :category: Causes a warning to be emitted if a literal will overflow, e.g. ``300 :: Word8``. .. ghc-flag:: -Wempty-enumerations + :shortdesc: warn about enumerations that are empty + :type: dynamic + :reverse: -Wno-empty-enumerations + :category: Causes a warning to be emitted if an enumeration is empty, e.g. ``[5 .. 3]``. .. ghc-flag:: -Wduplicate-constraints + :shortdesc: warn when a constraint appears duplicated in a type signature + :type: dynamic + :reverse: -Wno-duplicate-constraints + :category: .. index:: single: duplicate constraints, warning @@ -447,6 +643,11 @@ of ``-W(no-)*``. :ghc-flag:`-Wredundant-constraints`. .. ghc-flag:: -Wredundant-constraints + :shortdesc: Have the compiler warn about redundant constraints in type + signatures. + :type: dynamic + :reverse: -Wno-redundant-constraints + :category: :since: 8.0 @@ -492,6 +693,10 @@ of ``-W(no-)*``. constraint is needed, so no warning is issued. .. ghc-flag:: -Wduplicate-exports + :shortdesc: warn when an entity is exported multiple times + :type: dynamic + :reverse: -Wno-duplicate-exports + :category: .. index:: single: duplicate exports, warning @@ -505,6 +710,10 @@ of ``-W(no-)*``. This option is on by default. .. ghc-flag:: -Whi-shadowing + :shortdesc: warn when a ``.hi`` file in the current directory shadows a library + :type: dynamic + :reverse: -Wno-hi-shadowing + :category: .. index:: single: shadowing; interface files @@ -514,6 +723,11 @@ of ``-W(no-)*``. name in a library or other directory. .. ghc-flag:: -Widentities + :shortdesc: warn about uses of Prelude numeric conversions that are probably + the identity (and hence could be omitted) + :type: dynamic + :reverse: -Wno-identities + :category: Causes the compiler to emit a warning when a Prelude numeric conversion converts a type ``T`` to the same type ``T``; such calls are @@ -521,27 +735,34 @@ of ``-W(no-)*``. ``toInteger``, ``toRational``, ``fromIntegral``, and ``realToFrac``. .. ghc-flag:: -Wimplicit-prelude + :shortdesc: warn when the Prelude is implicitly imported + :type: dynamic + :reverse: -Wno-implicit-prelude + :category: .. index:: single: implicit prelude, warning - Have the compiler warn if the Prelude is implicitly imported. This - happens unless either the Prelude module is explicitly imported with - an ``import ... Prelude ...`` line, or this implicit import is - disabled (either by :ghc-flag:`-XNoImplicitPrelude` or a - ``LANGUAGE NoImplicitPrelude`` pragma). + Have the compiler warn if the Prelude is implicitly imported. This happens + unless either the Prelude module is explicitly imported with an ``import + ... Prelude ...`` line, or this implicit import is disabled (either by + :ghc-flag:`-XNoImplicitPrelude` or a ``LANGUAGE NoImplicitPrelude`` + pragma). - Note that no warning is given for syntax that implicitly refers to - the Prelude, even if :ghc-flag:`-XNoImplicitPrelude` would change whether it - refers to the Prelude. For example, no warning is given when ``368`` - means ``Prelude.fromInteger (368::Prelude.Integer)`` (where - ``Prelude`` refers to the actual Prelude module, regardless of the - imports of the module being compiled). + Note that no warning is given for syntax that implicitly refers to the + Prelude, even if :ghc-flag:`-XNoImplicitPrelude` would change whether it + refers to the Prelude. For example, no warning is given when ``368`` means + ``Prelude.fromInteger (368::Prelude.Integer)`` (where ``Prelude`` refers + to the actual Prelude module, regardless of the imports of the module + being compiled). This warning is off by default. .. ghc-flag:: -Wincomplete-patterns - -Wincomplete-uni-patterns + :shortdesc: warn when a pattern match could fail + :type: dynamic + :reverse: -Wno-incomplete-patterns + :category: .. index:: single: incomplete patterns, warning @@ -559,14 +780,26 @@ of ``-W(no-)*``. generally considered good practice to cover all the cases in your functions, and it is switched on by :ghc-flag:`-W`. - The flag :ghc-flag:`-Wincomplete-uni-patterns` is similar, except that - it applies only to lambda-expressions and pattern bindings, - constructs that only allow a single pattern: :: + +.. ghc-flag:: -Wincomplete-uni-patterns + :shortdesc: warn when a pattern match in a lambda expression or + pattern binding could fail + :type: dynamic + :reverse: -Wno-incomplete-uni-patterns + :category: + + The flag :ghc-flag:`-Wincomplete-uni-patterns` is similar to + :ghc-flag:`-Wincomplete-patterns`, except that it applies only to + lambda-expressions and pattern bindings, constructs that only allow a + single pattern: :: h = \[] -> 2 Just k = f y .. ghc-flag:: -fmax-pmcheck-iterations=⟨n⟩ + :shortdesc: the iteration limit for the pattern match checker + :type: dynamic + :category: :default: 2000000 @@ -579,6 +812,10 @@ of ``-W(no-)*``. pattern match, for the sake of future readers of your code. .. ghc-flag:: -Wincomplete-record-updates + :shortdesc: warn when a record update could fail + :type: dynamic + :reverse: -Wno-incomplete-record-updates + :category: .. index:: single: incomplete record updates, warning @@ -598,6 +835,10 @@ of ``-W(no-)*``. and it often doesn't indicate a bug in the program. .. ghc-flag:: -Wmissing-fields + :shortdesc: warn when fields of a record are uninitialised + :type: dynamic + :reverse: -Wno-missing-fields + :category: .. index:: single: missing fields, warning @@ -610,6 +851,11 @@ of ``-W(no-)*``. programmer error. .. ghc-flag:: -Wmissing-import-lists + :shortdesc: warn when an import declaration does not explicitly list all the + names brought into scope + :type: dynamic + :reverse: -fnowarn-missing-import-lists + :category: .. index:: single: missing import lists, warning @@ -632,6 +878,10 @@ of ``-W(no-)*``. unlikely to produce ambiguity in ``M``. .. ghc-flag:: -Wmissing-methods + :shortdesc: warn when class methods are undefined + :type: dynamic + :reverse: -Wno-missing-methods + :category: .. index:: single: missing methods, warning @@ -658,6 +908,10 @@ of ``-W(no-)*``. :ref:`minimal-pragma`. .. ghc-flag:: -Wmissing-signatures + :shortdesc: warn about top-level functions without signatures + :type: dynamic + :reverse: -Wno-missing-signatures + :category: .. index:: single: type signatures, missing @@ -668,6 +922,12 @@ of ``-W(no-)*``. option is off by default. .. ghc-flag:: -Wmissing-exported-sigs + :shortdesc: *(deprecated)* + warn about top-level functions without signatures, only if they + are exported. takes precedence over -Wmissing-signatures + :type: dynamic + :reverse: -Wno-missing-exported-sigs + :category: .. index:: single: type signatures, missing @@ -676,6 +936,11 @@ of ``-W(no-)*``. :ghc-flag:`-Wmissing-exported-signatures`. .. ghc-flag:: -Wmissing-exported-signatures + :shortdesc: warn about top-level functions without signatures, only if they + are exported. takes precedence over -Wmissing-signatures + :type: dynamic + :reverse: -Wno-missing-exported-signatures + :category: .. index:: single: type signatures, missing @@ -688,6 +953,11 @@ of ``-W(no-)*``. reports the inferred type. The option is off by default. .. ghc-flag:: -Wmissing-local-sigs + :shortdesc: *(deprecated)* + warn about polymorphic local bindings without signatures + :type: dynamic + :reverse: -Wno-missing-local-sigs + :category: .. index:: single: type signatures, missing @@ -696,6 +966,10 @@ of ``-W(no-)*``. :ghc-flag:`-Wmissing-local-signatures`. .. ghc-flag:: -Wmissing-local-signatures + :shortdesc: warn about polymorphic local bindings without signatures + :type: dynamic + :reverse: -Wno-missing-local-signatures + :category: .. index:: single: type signatures, missing @@ -706,6 +980,10 @@ of ``-W(no-)*``. default. .. ghc-flag:: -Wmissing-pattern-synonym-signatures + :shortdesc: warn when pattern synonyms do not have type signatures + :type: dynamic + :reverse: -Wno-missing-pattern-synonym-signatures + :category: .. index:: single: type signatures, missing, pattern synonyms @@ -719,6 +997,10 @@ of ``-W(no-)*``. type. This option is off by default. .. ghc-flag:: -Wname-shadowing + :shortdesc: warn when names are shadowed + :type: dynamic + :reverse: -Wno-name-shadowing + :category: .. index:: single: shadowing, warning @@ -736,6 +1018,11 @@ of ``-W(no-)*``. f x = do { _ignore <- this; _ignore <- that; return (the other) } .. ghc-flag:: -Worphans + :shortdesc: warn when the module contains :ref:`orphan instance declarations + or rewrite rules <orphan-modules>` + :type: dynamic + :reverse: -Wno-orphans + :category: .. index:: single: orphan instances, warning @@ -758,6 +1045,10 @@ of ``-W(no-)*``. instances. .. ghc-flag:: -Woverlapping-patterns + :shortdesc: warn about overlapping patterns + :type: dynamic + :reverse: -Wno-overlapping-patterns + :category: .. index:: single: overlapping patterns, warning @@ -776,6 +1067,11 @@ of ``-W(no-)*``. is a programmer mistake/error, so this option is enabled by default. .. ghc-flag:: -Wsimplifiable-class-constraints + :shortdesc: 2arn about class constraints in a type signature that can + be simplified using a top-level instance declaration. + :type: dynamic + :reverse: -Wno-overlapping-patterns + :category: :since: 8.2 @@ -799,6 +1095,10 @@ of ``-W(no-)*``. <-Wsimplifiable-class-constraints>`. .. ghc-flag:: -Wtabs + :shortdesc: warn if there are tabs in the source file + :type: dynamic + :reverse: -Wno-tabs + :category: .. index:: single: tabs, warning @@ -806,6 +1106,10 @@ of ``-W(no-)*``. Have the compiler warn if there are tabs in your source file. .. ghc-flag:: -Wtype-defaults + :shortdesc: warn when defaulting happens + :type: dynamic + :reverse: -Wno-type-defaults + :category: .. index:: single: defaulting mechanism, warning @@ -822,6 +1126,10 @@ of ``-W(no-)*``. This warning is off by default. .. ghc-flag:: -Wmonomorphism-restriction + :shortdesc: warn when the Monomorphism Restriction is applied + :type: dynamic + :reverse: -Wno-monomorphism-restriction + :category: .. index:: single: monomorphism restriction, warning @@ -834,10 +1142,19 @@ of ``-W(no-)*``. This warning is off by default. .. ghc-flag:: -Wunsupported-llvm-version + :shortdesc: Warn when using :ghc-flag:`-fllvm` with an unsupported + version of LLVM. + :type: dynamic + :reverse: -Wno-monomorphism-restriction + :category: Warn when using :ghc-flag:`-fllvm` with an unsupported version of LLVM. .. ghc-flag:: -Wunticked-promoted-constructors + :shortdesc: warn if promoted constructors are not ticked + :type: dynamic + :reverse: -Wno-unticked-promoted-constructors + :category: .. index:: single: promoted constructor, warning @@ -859,6 +1176,12 @@ of ``-W(no-)*``. This warning is enabled by default in :ghc-flag:`-Wall` mode. .. ghc-flag:: -Wunused-binds + :shortdesc: warn about bindings that are unused. Alias for + :ghc-flag:`-Wunused-top-binds`, :ghc-flag:`-Wunused-local-binds` and + :ghc-flag:`-Wunused-pattern-binds` + :type: dynamic + :reverse: -Wno-unused-binds + :category: .. index:: single: unused binds, warning @@ -872,6 +1195,10 @@ of ``-W(no-)*``. - :ghc-flag:`-Wunused-pattern-binds` .. ghc-flag:: -Wunused-top-binds + :shortdesc: warn about top-level bindings that are unused + :type: dynamic + :reverse: -Wno-unused-top-binds + :category: .. index:: single: unused binds, warning @@ -902,6 +1229,10 @@ of ``-W(no-)*``. _w = True -- No warning: _w starts with an underscore .. ghc-flag:: -Wunused-local-binds + :shortdesc: warn about local bindings that are unused + :type: dynamic + :reverse: -Wno-unused-local-binds + :category: .. index:: single: unused binds, warning @@ -914,6 +1245,10 @@ of ``-W(no-)*``. g = h x -- No warning: g is unused, but is a top-level binding .. ghc-flag:: -Wunused-pattern-binds + :shortdesc: warn about pattern match bindings that are unused + :type: dynamic + :reverse: -Wno-unused-pattern-binds + :category: .. index:: single: unused binds, warning @@ -936,6 +1271,10 @@ of ``-W(no-)*``. it forces evaluation, and is useful as an alternative to ``seq``. .. ghc-flag:: -Wunused-imports + :shortdesc: warn about unnecessary imports + :type: dynamic + :reverse: -Wno-unused-imports + :category: .. index:: single: unused imports, warning @@ -947,6 +1286,10 @@ of ``-W(no-)*``. declarations, which are anonymous in Haskell. .. ghc-flag:: -Wunused-matches + :shortdesc: warn about variables in patterns that aren't used + :type: dynamic + :reverse: -Wno-unused-matches + :category: .. index:: single: unused matches, warning @@ -965,6 +1308,11 @@ of ``-W(no-)*``. :ghc-flag:`-Wunused-type-patterns` flag. .. ghc-flag:: -Wunused-do-bind + :shortdesc: warn about do bindings that appear to throw away values of types + other than ``()`` + :type: dynamic + :reverse: -Wno-unused-do-bind + :category: .. index:: single: unused do binding, warning @@ -986,6 +1334,11 @@ of ``-W(no-)*``. do { mapM_ popInt xs ; return 10 } .. ghc-flag:: -Wunused-type-patterns + :shortdesc: warn about unused type variables which arise from patterns + in type family and data family instances + :type: dynamic + :reverse: -Wno-unused-type-patterns + :category: .. index:: single: unused type patterns, warning @@ -1008,6 +1361,11 @@ of ``-W(no-)*``. documentation harder to read. .. ghc-flag:: -Wunused-foralls + :shortdesc: warn about type variables in user-written + ``forall``\\s that are unused + :type: dynamic + :reverse: -Wno-unused-foralls + :category: .. index:: single: unused foralls, warning @@ -1021,6 +1379,11 @@ of ``-W(no-)*``. would report ``a`` and ``c`` as unused. .. ghc-flag:: -Wwrong-do-bind + :shortdesc: warn about do bindings that appear to throw away monadic values + that you should have bound instead + :type: dynamic + :reverse: -Wno-wrong-do-bind + :category: .. index:: single: apparently erroneous do binding, warning @@ -1044,12 +1407,21 @@ of ``-W(no-)*``. do { popInt 10 ; return 10 } .. ghc-flag:: -Winline-rule-shadowing + :shortdesc: Warn if a rewrite RULE might fail to fire because the + function might be inlined before the rule has a chance to fire. + See :ref:`rules-inline`. + :type: dynamic + :reverse: -Wno-inline-rule-shadowing + :category: Warn if a rewrite RULE might fail to fire because the function might be inlined before the rule has a chance to fire. See :ref:`rules-inline`. .. ghc-flag:: -Wcpp-undef + :shortdesc: warn on uses of the `#if` directive on undefined identifiers + :type: dynamic + :category: :since: 8.2 @@ -1058,12 +1430,24 @@ of ``-W(no-)*``. undefined identifiers. .. ghc-flag:: -Wunbanged-strict-patterns + :shortdesc: warn on pattern bind of unlifted variable that is neither bare + nor banged + :type: dynamic + :reverse: -Wno-unbanged-strict-patterns + :category: This flag warns whenever you write a pattern that binds a variable whose type is unlifted, and yet the pattern is not a bang pattern nor a bare variable. See :ref:`glasgow-unboxed` for information about unlifted types. .. ghc-flag:: -Wmissing-home-modules + :shortdesc: warn when encountering a home module imported, but not listed + on the command line. Useful for cabal to ensure GHC won't pick + up modules, not listed neither in ``exposed-modules``, nor in + ``other-modules``. + :type: dynamic + :reverse: -Wno-missing-home-modules + :category: :since: 8.2 |