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* Warn if unicode bidirectional formatting characters are found in the source ↵Zubin Duggal2021-10-261-0/+18
| | | | (#20263)
* Emit warning if bang is applied to unlifted typesTito Sacchi2021-09-171-0/+14
| | | | | | | | | | | | | | | | GHC will trigger a warning similar to the following when a strictness flag is applied to an unlifted type (primitive or defined with the Unlifted* extensions) in the definition of a data constructor. Test.hs:7:13: warning: [-Wredundant-strictness-flags] • Strictness flag has no effect on unlifted type ‘Int#’ • In the definition of data constructor ‘TestCon’ In the data type declaration for ‘Test’ | 7 | data Test = TestCon !Int# | ^^^^^^^^^^^^^ Fixes #20187
* Docs: use :default: and :ghc-ticket:Krzysztof Gogolewski2021-07-281-47/+52
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* Re #18087 !6238 Empty line in front of :since:Andreas Abel2021-07-271-0/+3
| | | | Ack. @monoidal
* Issue #18087: :since: for warnings of ghc 6/7/8Andreas Abel2021-07-271-0/+113
| | | | | | | | | | | Added :since: fields to users_guide on warning, for warnings introduced starting GHC 6.0. The data was extracted from the HTML docs on warnings, see https://gitlab.haskell.org/ghc/ghc/-/issues/18087 and partially verified by consulting the change logs.
* Doc: warnings: since: remove minor version number for uniformityAndreas Abel2021-07-271-5/+5
| | | | | New warnings are only released in major versions, it seems. One way or the other, a .1 minor version can always be dropped.
* Doc: tabs to spacesAndreas Abel2021-07-271-2/+2
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* Typos, minor comment fixesKrzysztof Gogolewski2021-06-221-2/+2
| | | | | | | | | | | | | | | | | | | - Remove fstName, sndName, fstIdKey, sndIdKey - no longer used, removed from basicKnownKeyNames - Remove breakpointId, breakpointCondId, opaqueTyCon, unknownTyCon - they were used in the old implementation of the GHCi debugger - Fix typos in comments - Remove outdated comment in Lint.hs - Use 'LitRubbish' instead of 'RubbishLit' for consistency - Remove comment about subkinding - superseded by Note [Kind Constraint and kind Type] - Mention ticket ID in a linear types error message - Fix formatting in using-warnings.rst and linear-types.rst - Remove comment about 'Any' in Dynamic.hs - Dynamic now uses Typeable + existential instead of Any - Remove codeGen/should_compile/T13233.hs This was added by accident, it is not used and T13233 is already in should_fail
* Deprecate -Wmissing-monadfail-instances (#17875)Krzysztof Gogolewski2021-06-191-41/+23
| | | | | Also document deprecation of Wnoncanonical-monadfail-instances and -Wimplicit-kind-vars
* Add -Wmissing-exported-pattern-synonym-signaturesThomas Winant2021-05-291-0/+18
| | | | | | | | | | | | | After !4741, it was no longer possible to silence a warning about a missing pattern synonym signature if the `-Wmissing-signatures` flag was on. Restore the previous semantics while still adhering to the principle "enabling an additional warning flag should never make prior warnings disappear". For more symmetry and granularity, introduce `-Wmissing-exported-pattern-synonym-signatures`. See Note [Missing signatures] for an overview of all flags involved.
* Data.List specialization to []Oleg Grenrus2021-04-011-7/+2
| | | | | | | - Remove GHC.OldList - Remove Data.OldList - compat-unqualified-imports is no-op - update haddock submodule
* Implement -Wmissing-kind-signaturesOleg Grenrus2021-03-251-0/+27
| | | | Fixes #19564
* Add a Template Haskell warning flag -Wimplicit-liftKrzysztof Gogolewski2021-03-041-0/+17
| | | | Part of #17804.
* Fix typo in docs [skip ci]Sebastian Graf2021-03-031-1/+1
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* Pmc: Implement `considerAccessible` (#18610)Sebastian Graf2021-03-011-0/+28
| | | | | | | | | | | | | | | | | | | | | | | | | | Consider (`T18610`): ```hs f :: Bool -> Int f x = case (x, x) of (True, True) -> 1 (False, False) -> 2 (True, False) -> 3 -- Warning: Redundant ``` The third clause will be flagged as redundant. Nevertheless, the programmer might intend to keep the clause in order to avoid bitrot. After this patch, the programmer can write ```hs g :: Bool -> Int g x = case (x, x) of (True, True) -> 1 (False, False) -> 2 (True, False) | GHC.Exts.considerAccessible -> 3 -- No warning ``` And won't be bothered any longer. See also `Note [considerAccessible]` and the updated entries in the user's guide. Fixes #18610 and #19228.
* Implement -Wambiguous-fieldsAdam Gundry2021-02-261-0/+20
| | | | | | Fixes #18966. Adds a new warning -Wambiguous-fields for uses of field selectors or record updates that will be rejected in the future, when the DuplicateRecordFields extension is simplified per https://github.com/ghc-proposals/ghc-proposals/pull/366.
* Prefer -Wmissing-signatures over -Wmissing-exported-signatures (#14794)Michiel de Bruijne2021-02-221-3/+4
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* Add -Wsafe to flags not enabled by -WallFendor2021-02-101-0/+1
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* Documentation fixesKrzysztof Gogolewski2021-01-301-3/+3
| | | | | | | | | | | | | | | - Add missing :since: for NondecreasingIndentation and OverlappingInstances - Remove duplicated descriptions for Safe Haskell flags and UndecidableInstances. Instead, the sections contain a link. - compare-flags: Also check for options supported by ghci. This uncovered two more that are not documented. The flag -smp was removed. - Formatting fixes - Remove the warning about -XNoImplicitPrelude - it was written in 1996, the extension is no longer dangerous. - Fix misspelled :reverse: flags Fixes #18958.
* Add two warnings to -WallTom Ellis2020-12-191-2/+0
| | | | | | | * -Wincomplete-uni-patterns * -Wincomplete-record-updates See https://gitlab.haskell.org/ghc/ghc/-/issues/15656
* Implement -Woperator-whitespace (#18834)Vladislav Zavialov2020-10-191-0/+52
| | | | | | | | | | | | | | This patch implements two related warnings: -Woperator-whitespace-ext-conflict warns on uses of infix operators that would be parsed differently were a particular GHC extension enabled -Woperator-whitespace warns on prefix, suffix, and tight infix uses of infix operators Updates submodules: haddock, containers.
* Document -Wderiving-typeableMaxGabriel2020-10-091-0/+14
| | | | Tracking: #18641
* Document profiling flags, warning flags, and no-pieRachel2020-10-071-31/+86
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* Small documentation fixesKrzysztof Gogolewski2020-10-031-2/+6
| | | | | | | | | - Fix formatting of code blocks and a few sphinx warnings - Move the Void# change to 9.2, it was done right after the branch was cut - Fix typo in linear types documentation - Note that -Wincomplete-uni-patterns affects lazy patterns [skip ci]
* Implement -Wredundant-bang-patterns (#17340)nineonine2020-08-191-0/+41
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add new flag '-Wredundant-bang-patterns' that enables checks for "dead" bangs. Dead bangs are the ones that under no circumstances can force a thunk that wasn't already forced. Dead bangs are a form of redundant bangs. The new check is performed in Pattern-Match Coverage Checker along with other checks (namely, redundant and inaccessible RHSs). Given f :: Bool -> Int f True = 1 f !x = 2 we can detect dead bang patterns by checking whether @x ~ ⊥@ is satisfiable where the PmBang appears in 'checkGrdTree'. If not, then clearly the bang is dead. Such a dead bang is then indicated in the annotated pattern-match tree by a 'RedundantSrcBang' wrapping. In 'redundantAndInaccessibles', we collect all dead bangs to warn about. Note that we don't want to warn for a dead bang that appears on a redundant clause. That is because in that case, we recommend to delete the clause wholly, including its leading pattern match. Dead bang patterns are redundant. But there are bang patterns which are redundant that aren't dead, for example f !() = 0 the bang still forces the match variable, before we attempt to match on (). But it is redundant with the forcing done by the () match. We currently don't detect redundant bangs that aren't dead.
* users-guide: Rename 8.12 to 9.0Takenobu Tani2020-08-061-1/+1
| | | | | | | | | GHC 8.12.1 has been renamed to GHC 9.0.1. See also: https://mail.haskell.org/pipermail/ghc-devs/2020-July/019083.html [skip ci]
* Replace broken links to old haskell-prime site by working links to gitlab ↵BinderDavid2020-07-221-1/+1
| | | | | | instance. [skip ci]
* Accumulate Haddock comments in P (#17544, #17561, #8944)Vladislav Zavialov2020-07-211-0/+19
| | | | | | | | | | | | | | | | | | Haddock comments are, first and foremost, comments. It's very annoying to incorporate them into the grammar. We can take advantage of an important property: adding a Haddock comment does not change the parse tree in any way other than wrapping some nodes in HsDocTy and the like (and if it does, that's a bug). This patch implements the following: * Accumulate Haddock comments with their locations in the P monad. This is handled in the lexer. * After parsing, do a pass over the AST to associate Haddock comments with AST nodes using location info. * Report the leftover comments to the user as a warning (-Winvalid-haddock).
* Mention flags that are not enabled by -Wall (#18372)Valery Tolstov2020-07-031-1/+5
| | | | | * Mention missing flags that are not actually enabled by -Wall (docs/users_guide/using-warnings.rst) * Additionally remove -Wmissing-monadfail-instances from the list of flags enabled by -Wcompat, as it is not the case since 8.8
* docs: fix formatting in users guideAdam Sandberg Ericsson2020-06-171-2/+1
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* Enable -Wstar-is-type in -WallBen Gamari2020-02-201-1/+0
| | | | | | | | | | As noted in [proposal 0143][proposal] this is supposed to happen in 8.12. Also fix an incorrect claim in the users guide that -Wstar-is-type is enabled by default. [proposal]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0143-remove-star-kind.rst
* Fix flag documentation (#17826)Sylvain Henry2020-02-131-2/+4
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* Introduce -Wcompat-unqualified-importsBen Gamari2020-02-081-3/+22
| | | | | | | | | | | | | This implements the warning proposed in option (B) of the Data.List.singleton CLC [discussion][]. This warning, which is included in `-Wcompat` is intended to help users identify imports of modules that will change incompatibly in future GHC releases. This currently only includes `Data.List` due to the expected specialisation and addition of `Data.List.singleton`. Fixes #17244. [discussion]: https://groups.google.com/d/msg/haskell-core-libraries/q3zHLmzBa5E/PmlAs_kYAQAJ
* PmCheck: Formulate as translation between Clause TreesSebastian Graf2020-01-251-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We used to check `GrdVec`s arising from multiple clauses and guards in isolation. That resulted in a split between `pmCheck` and `pmCheckGuards`, the implementations of which were similar, but subtly different in detail. Also the throttling mechanism described in `Note [Countering exponential blowup]` ultimately got quite complicated because it had to cater for both checking functions. This patch realises that pattern match checking doesn't just consider single guarded RHSs, but that it's always a whole set of clauses, each of which can have multiple guarded RHSs in turn. We do so by translating a list of `Match`es to a `GrdTree`: ```haskell data GrdTree = Rhs !RhsInfo | Guard !PmGrd !GrdTree -- captures lef-to-right match semantics | Sequence !GrdTree !GrdTree -- captures top-to-bottom match semantics | Empty -- For -XEmptyCase, neutral element of Sequence ``` Then we have a function `checkGrdTree` that matches a given `GrdTree` against an incoming set of values, represented by `Deltas`: ```haskell checkGrdTree :: GrdTree -> Deltas -> CheckResult ... ``` Throttling is isolated to the `Sequence` case and becomes as easy as one would expect: When the union of uncovered values becomes too big, just return the original incoming `Deltas` instead (which is always a superset of the union, thus a sound approximation). The returned `CheckResult` contains two things: 1. The set of values that were not covered by any of the clauses, for exhaustivity warnings. 2. The `AnnotatedTree` that enriches the syntactic structure of the input program with divergence and inaccessibility information. This is `AnnotatedTree`: ```haskell data AnnotatedTree = AccessibleRhs !RhsInfo | InaccessibleRhs !RhsInfo | MayDiverge !AnnotatedTree | SequenceAnn !AnnotatedTree !AnnotatedTree | EmptyAnn ``` Crucially, `MayDiverge` asserts that the tree may force diverging values, so not all of its wrapped clauses can be redundant. While the set of uncovered values can be used to generate the missing equations for warning messages, redundant and proper inaccessible equations can be extracted from `AnnotatedTree` by `redundantAndInaccessibleRhss`. For this to work properly, the interface to the Oracle had to change. There's only `addPmCts` now, which takes a bag of `PmCt`s. There's a whole bunch of `PmCt` variants to replace the different oracle functions from before. The new `AnnotatedTree` structure allows for more accurate warning reporting (as evidenced by a number of changes spread throughout GHC's code base), thus we fix #17465. Fixes #17646 on the go. Metric Decrease: T11822 T9233 PmSeriesS haddock.compiler
* Fix typos, via a Levenshtein-style correctorBrian Wignall2020-01-041-1/+1
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* Whitespace-sensitive bang patterns (#1087, #17162)wip/whitespace-and-lookaheadVladislav Zavialov2019-11-271-7/+0
| | | | | | | | | | | | | | | | | | This patch implements a part of GHC Proposal #229 that covers five operators: * the bang operator (!) * the tilde operator (~) * the at operator (@) * the dollar operator ($) * the double dollar operator ($$) Based on surrounding whitespace, these operators are disambiguated into bang patterns, lazy patterns, strictness annotations, type applications, splices, and typed splices. This patch doesn't cover the (-) operator or the -Woperator-whitespace warning, which are left as future work.
* Add back documentation for deprecated -Whi-shadowingLuke Lau2019-10-271-0/+17
| | | | | | This was removed in b538476be3706264620c072e6e436debf9e0d3e4, but without it the compare-flags.py script fails. This adds it back and marks it as deprecated, with a notice that it is slated for removal.
* users-guide: Fix :since: for -Wunused-packagesBen Gamari2019-10-231-1/+1
| | | | Fixes #17382.
* users-guide: Fix various warningsBen Gamari2019-10-081-9/+27
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* users-guide: Refer to language extension flags via :extension:Ben Gamari2019-10-081-8/+8
| | | | Previously several were referred to via :ghc-flag:`-X...`.
* Deprecate -fwarn-hi-shadowing, because it was never implemented and isDaroc Alden2019-10-041-13/+0
| | | | | | not used. This fixes #10913.
* PmCheck: Elaborate what 'model' means in the user guide [skip ci]Sebastian Graf2019-09-271-8/+14
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* PmCheck: Only ever check constantly many models against a single patternSebastian Graf2019-09-251-10/+12
| | | | | | | | | | | | | | | | | | | | | | | | | Introduces a new flag `-fmax-pmcheck-deltas` to achieve that. Deprecates the old `-fmax-pmcheck-iter` mechanism in favor of this new flag. From the user's guide: Pattern match checking can be exponential in some cases. This limit makes sure we scale polynomially in the number of patterns, by forgetting refined information gained from a partially successful match. For example, when matching `x` against `Just 4`, we split each incoming matching model into two sub-models: One where `x` is not `Nothing` and one where `x` is `Just y` but `y` is not `4`. When the number of incoming models exceeds the limit, we continue checking the next clause with the original, unrefined model. This also retires the incredibly hard to understand "maximum number of refinements" mechanism, because the current mechanism is more general and should catch the same exponential cases like PrelRules at the same time. ------------------------- Metric Decrease: T11822 -------------------------
* Add -Wderiving-defaults (#15839)Kari Pahula2019-09-251-0/+18
| | | | | | Enabling both DeriveAnyClass and GeneralizedNewtypeDeriving can cause a warning when no explicit deriving strategy is in use. This change adds an enable/suppress flag for it.
* Warn about unused packagesYuras Shumovich2019-06-111-0/+15
| | | | | | | | | | | | Reviewers: bgamari, simonpj Reviewed By: simonpj Subscribers: hvr, simonpj, mpickering, rwbarton, carter GHC Trac Issues: #15838 Differential Revision: https://phabricator.haskell.org/D5285
* Minor spelling fixes to users guide.P.C. Shyamshankar2019-05-291-1/+1
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* users-guide: Fix directive errors on 8.10Takenobu Tani2019-05-211-2/+4
| | | | | | | | | | | The following sections are not displayed due to a directive error: * -Wunused-record-wildcards * -Wredundant-record-wildcards I changed the location of the `since` directive. [skip ci]
* users-guide: Fix typoNathan Collins2019-04-031-1/+1
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* Treat kind/type variables identically, demolish FKTVVladislav Zavialov2019-02-271-53/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implements GHC Proposal #24: .../ghc-proposals/blob/master/proposals/0024-no-kind-vars.rst Fixes Trac #16334, Trac #16315 With this patch, scoping rules for type and kind variables have been unified: kind variables no longer receieve special treatment. This simplifies both the language and the implementation. User-facing changes ------------------- * Kind variables are no longer implicitly quantified when an explicit forall is used: p :: Proxy (a :: k) -- still accepted p :: forall k a. Proxy (a :: k) -- still accepted p :: forall a. Proxy (a :: k) -- no longer accepted In other words, now we adhere to the "forall-or-nothing" rule more strictly. Related function: RnTypes.rnImplicitBndrs * The -Wimplicit-kind-vars warning has been deprecated. * Kind variables are no longer implicitly quantified in constructor declarations: data T a = T1 (S (a :: k) | forall (b::k). T2 (S b) -- no longer accepted data T (a :: k) = T1 (S (a :: k) | forall (b::k). T2 (S b) -- still accepted Related function: RnTypes.extractRdrKindSigVars * Implicitly quantified kind variables are no longer put in front of other variables: f :: Proxy (a :: k) -> Proxy (b :: j) f :: forall k j (a :: k) (b :: j). Proxy a -> Proxy b -- old order f :: forall k (a :: k) j (b :: j). Proxy a -> Proxy b -- new order This is a breaking change for users of TypeApplications. Note that we still respect the dpendency order: 'k' before 'a', 'j' before 'b'. See "Ordering of specified variables" in the User's Guide. Related function: RnTypes.rnImplicitBndrs * In type synonyms and type family equations, free variables on the RHS are no longer implicitly quantified unless used in an outermost kind annotation: type T = Just (Nothing :: Maybe a) -- no longer accepted type T = Just Nothing :: Maybe (Maybe a) -- still accepted The latter form is a workaround due to temporary lack of an explicit quantification method. Ideally, we would write something along these lines: type T @a = Just (Nothing :: Maybe a) Related function: RnTypes.extractHsTyRdrTyVarsKindVars * Named wildcards in kinds are fixed (Trac #16334): x :: (Int :: _t) -- this compiles, infers (_t ~ Type) Related function: RnTypes.partition_nwcs Implementation notes -------------------- * One of the key changes is the removal of FKTV in RnTypes: - data FreeKiTyVars = FKTV { fktv_kis :: [Located RdrName] - , fktv_tys :: [Located RdrName] } + type FreeKiTyVars = [Located RdrName] We used to keep track of type and kind variables separately, but now that they are on equal footing when it comes to scoping, we can put them in the same list. * extract_lty and family are no longer parametrized by TypeOrKind, as we now do not distinguish kind variables from type variables. * PatSynExPE and the related Note [Pattern synonym existentials do not scope] have been removed (Trac #16315). With no implicit kind quantification, we can no longer trigger the error. * reportFloatingKvs and the related Note [Free-floating kind vars] have been removed. With no implicit kind quantification, we can no longer trigger the error.
* Implement -Wredundant-record-wildcards and -Wunused-record-wildcardsMatthew Pickering2019-02-141-3/+47
| | | | | | | | | -Wredundant-record-wildcards warns when a .. pattern binds no variables. -Wunused-record-wildcards warns when none of the variables bound by a .. pattern are used. These flags are enabled by `-Wall`.
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