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* Change GHC.Prim to GHC.Exts in docs and testsKrzysztof Gogolewski2022-04-011-1/+0
| | | | | Users are supposed to import GHC.Exts rather than GHC.Prim. Part of #18749.
* Add test for #20562Oleg Grenrus2022-02-162-0/+16
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* Make implication tidying agree with Note [Tidying multiple names at once]Matthew Pickering2022-02-052-7/+7
| | | | | | | | | | | Note [Tidying multiple names at once] indicates that if multiple variables have the same name then we shouldn't prioritise one of them and instead rename them all to a1, a2, a3... etc This patch implements that change, some error message changes as expected. Closes #20932
* Use diagnostic infrastructure in GHC.Tc.Errorssheaf2022-01-1722-50/+65
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* Check quoted TH names are in the correct namespacesheaf2022-01-042-9/+9
| | | | | | | | | | | | When quoting (using a TH single or double quote) a built-in name such as the list constructor (:), we didn't always check that the resulting 'Name' was in the correct namespace. This patch adds a check in GHC.Rename.Splice to ensure we get a Name that is in the term-level/type-level namespace, when using a single/double tick, respectively. Fixes #20884.
* testsuite: Remove reqlib modifierMatthew Pickering2021-12-222-13/+0
| | | | | | | | | | | | | | | | | | | | The reqlib modifer was supposed to indicate that a test needed a certain library in order to work. If the library happened to be installed then the test would run as normal. However, CI has never run these tests as the packages have not been installed and we don't want out tests to depend on things which might get externally broken by updating the compiler. The new strategy is to run these tests in head.hackage, where the tests have been cabalised as well as possible. Some tests couldn't be transferred into the normal style testsuite but it's better than never running any of the reqlib tests. https://gitlab.haskell.org/ghc/head.hackage/-/merge_requests/169 A few submodules also had reqlib tests and have been updated to remove it. Closes #16264 #20032 #17764 #16561
* EPA: Get rid of bare SrcSpan's in the ParsedSourceAlan Zimmerman2021-11-021-1/+3
| | | | | | | | | | | | | The ghc-exactPrint library has had to re-introduce the relatavise phase. This is needed if you change the length of an identifier and want the layout to be preserved afterwards. It is not possible to relatavise a bare SrcSpan, so introduce `SrcAnn NoEpAnns` for them instead. Updates haddock submodule.
* EPA: Use LocatedA for ModuleNameAlan Zimmerman2021-10-241-1/+1
| | | | | This allows us to use an Anchor with a DeltaPos in it when exact printing.
* Refactor package importsSylvain Henry2021-10-221-1/+3
| | | | | | | | | Use an (Raw)PkgQual datatype instead of `Maybe FastString` to represent package imports. Factorize the code that renames RawPkgQual into PkgQual in function `rnPkgQual`. Renaming consists in checking if the FastString is the magic "this" keyword, the home-unit unit-id or something else. Bump haddock submodule
* fuzzyLookup: More deterministic orderJoachim Breitner2021-10-141-1/+1
| | | | | | else the output may depend on the input order, which seems it may depend on the concrete Uniques, which is causing headaches when including test cases about that.
* Eradicate TcRnUnknownMessage from GHC.Tc.DerivAlfredo Di Napoli2021-10-051-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This (big) commit finishes porting the GHC.Tc.Deriv module to support the new diagnostic infrastructure (#18516) by getting rid of the legacy calls to `TcRnUnknownMessage`. This work ended up being quite pervasive and touched not only the Tc.Deriv module but also the Tc.Deriv.Utils and Tc.Deriv.Generics module, which needed to be adapted to use the new infrastructure. This also required generalising `Validity`. More specifically, this is a breakdown of the work done: * Add and use the TcRnUselessTypeable data constructor * Add and use TcRnDerivingDefaults data constructor * Add and use the TcRnNonUnaryTypeclassConstraint data constructor * Add and use TcRnPartialTypeSignatures * Add T13324_compile2 test to test another part of the TcRnPartialTypeSignatures diagnostic * Add and use TcRnCannotDeriveInstance data constructor, which introduces a new data constructor to TcRnMessage called TcRnCannotDeriveInstance, which is further sub-divided to carry a `DeriveInstanceErrReason` which explains the reason why we couldn't derive a typeclass instance. * Add DerivErrSafeHaskellGenericInst data constructor to DeriveInstanceErrReason * Add DerivErrDerivingViaWrongKind and DerivErrNoEtaReduce * Introduce the SuggestExtensionInOrderTo Hint, which adds (and use) a new constructor to the hint type `LanguageExtensionHint` called `SuggestExtensionInOrderTo`, which can be used to give a bit more "firm" recommendations when it's obvious what the required extension is, like in the case for the `DerivingStrategies`, which automatically follows from having enabled both `DeriveAnyClass` and `GeneralizedNewtypeDeriving`. * Wildcard-free pattern matching in mk_eqn_stock, which removes `_` in favour of pattern matching explicitly on `CanDeriveAnyClass` and `NonDerivableClass`, because that determine whether or not we can suggest to the user `DeriveAnyClass` or not.
* EPA: correctly capture comments between 'where' and bindsAlan Zimmerman2021-09-171-1/+2
| | | | | | | | | | | | In the following foo = x where -- do stuff doStuff = do stuff The "-- do stuff" comment is captured in the HsValBinds. Closes #20297
* Add proper GHCHints for most PsMessage constructorswip/adinapoli-issue-20055Alfredo Di Napoli2021-07-123-5/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit adds proper hints to most diagnostic types in the `GHC.Parser.Errors.Types` module. By "proper" we mean that previous to this commit the hints were bundled together with the diagnostic message, whereas now we moved most of them as proper `[GhcHint]` in the implementation of `diagnosticHints`. More specifically, this is the list of constructors which now has proper hints: * PsErrIllegalBangPattern * PsWarnOperatorWhitespaceExtConflict * PsErrLambdaCase * PsErrIllegalPatSynExport * PsWarnOperatorWhitespace * PsErrMultiWayIf * PsErrIllegalQualifiedDo * PsErrNumUnderscores * PsErrLinearFunction * PsErrIllegalTraditionalRecordSyntax * PsErrIllegalExplicitNamespace * PsErrOverloadedRecordUpdateNotEnabled * PsErrIllegalDataTypeContext * PsErrSemiColonsInCondExpr * PsErrSemiColonsInCondCmd * PsWarnStarIsType * PsWarnImportPreQualified * PsErrImportPostQualified * PsErrEmptyDoubleQuotes * PsErrIllegalRoleName * PsWarnStarBinder For some reason, this patch increases the peak_megabyte_allocated of the T11545 test to 90 (from a baseline of 80) but that particular test doesn't emit any parsing diagnostic or hint and the metric increase happens only for the `aarch64-linux-deb10`. Metric Increase: T11545
* Fix issue 20038 - Change 'variable' -> 'variables'Edward2021-07-061-1/+1
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* Suggest similar names when reporting types in terms (#19978)Vladislav Zavialov2021-06-251-2/+3
| | | | This fixes an error message regression.
* visually align expected and actual modules nameiori tsu2021-05-031-1/+1
| | | | | | | | | | | | | | | | | | | | before: > /home/matt/Projects/persistent/persistent/Database/Persist/ImplicitIdDef.hs:1:8: error: > File name does not match module name: > Saw: ‘A.B.Module’ > Expected: ‘A.B.Motule’ > | > 1 | module A.B.Motule > | ^^^^^^^^^^> after: > /home/matt/Projects/persistent/persistent/Database/Persist/ImplicitIdDef.hs:1:8: error: > File name does not match module name: > Saw: ‘A.B.Module’ > Expected: ‘A.B.Motule’ > | > 1 | module A.B.Motule > | ^^^^^^^^^^>
* EPA: cleanups after the mergeAlan Zimmerman2021-04-191-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Remove EpaAnn type synonym, rename EpaAnn' to EpaAnn. Closes #19705 Updates haddock submodule -- Change data EpaAnchor = AR RealSrcSpan | AD DeltaPos To instead be data EpaAnchor = AnchorReal RealSrcSpan | AnchorDelta DeltaPos Closes #19699 -- Change data DeltaPos = DP { deltaLine :: !Int, deltaColumn :: !Int } To instead be data DeltaPos = SameLine { deltaColumn :: !Int } | DifferentLine { deltaLine :: !Int, startColumn :: !Int } Closes #19698 -- Also some clean-ups of unused parts of check-exact.
* EPA : Rename AnnComment to EpaCommentAlan Zimmerman2021-03-311-7/+7
| | | | Follow-up from !2418, see #19579
* EPA : Rename ApiAnn to EPAnnAlan Zimmerman2021-03-311-13/+13
| | | | | | Follow-up from !2418, see #19579 Updates haddock submodule
* EPA : Rename AddApiAnn to AddEpAnnAlan Zimmerman2021-03-311-1/+1
| | | | | | | As port of the process of migrating naming from API Annotations to exact print annotations (EPA) Follow-up from !2418, see #19579
* GHC Exactprint main commitAlan Zimmerman2021-03-201-17/+83
| | | | | | | | Metric Increase: T10370 parsing001 Updates haddock submodule
* Use GHC2021 as default languageJoachim Breitner2021-03-1013-28/+37
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* Fixes to dealing with the export of mainSimon Peyton Jones2021-03-091-2/+2
| | | | | | | | | | | | | | | | | | | | It's surprisingly tricky to deal with 'main' (#19397). This patch does quite bit of refactoring do to it right. Well, more-right anyway! The moving parts are documented in GHC.Tc.Module Note [Dealing with main] Some other oddments: * Rename tcRnExports to rnExports; no typechecking here! * rnExports now uses checkNoErrs rather than failIfErrsM; the former fails only if rnExports itself finds errors * Small improvements to tcTyThingCategory, which ultimately weren't important to the patch, but I've retained as a minor improvement.
* Fix tests relying on same-line diagnostic orderingAlfredo Di Napoli2021-01-221-4/+5
| | | | | | | | This commit fixes 19 tests which were failing due to the use of `consBag` / `snocBag`, which have been now replaced by `addMessage`. This means that now GHC would output things in different order but only for /diagnostics on the same line/, so this is just reflecting that. The "normal" order of messages is still guaranteed.
* Fix bad span calculations of post qualified importsShayne Fletcher2020-12-053-0/+68
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* Fall back to types when looking up data constructors (#18740)wip/ghc-18740-lookup-updateDaniel Rogozin2020-10-112-3/+11
| | | | | | | | | | | | | | | | | | | | Before this patch, referring to a data constructor in a term-level context led to a scoping error: ghci> id Int <interactive>:1:4: error: Data constructor not in scope: Int After this patch, the renamer falls back to the type namespace and successfully finds the Int. It is then rejected in the type checker with a more useful error message: <interactive>:1:4: error: • Illegal term-level use of the type constructor ‘Int’ imported from ‘Prelude’ (and originally defined in ‘GHC.Types’) • In the first argument of ‘id’, namely ‘Int’ In the expression: id Int We also do this for type variables.
* PmCheck: Big refactor using guard tree variants more closely following ↵Sebastian Graf2020-09-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | source syntax (#18565) Previously, we desugared and coverage checked plain guard trees as described in Lower Your Guards. That caused (in !3849) quite a bit of pain when we need to partially recover tree structure of the input syntax to return covered sets for long-distance information, for example. In this refactor, I introduced a guard tree variant for each relevant source syntax component of a pattern-match (mainly match groups, match, GRHS, empty case, pattern binding). I made sure to share as much coverage checking code as possible, so that the syntax-specific checking functions are just wrappers around the more substantial checking functions for the LYG primitives (`checkSequence`, `checkGrds`). The refactoring payed off in clearer code and elimination of all panics related to assumed guard tree structure and thus fixes #18565. I also took the liberty to rename and re-arrange the order of functions and comments in the module, deleted some dead and irrelevant Notes, wrote some new ones and gave an overview module haddock.
* gitlab-ci: Bump Docker imagesBen Gamari2020-09-091-0/+1
| | | | | | | We now generate our Docker images via Dhall definitions, as described in ghc/ci-images!52. Additionally, we are far more careful about where tools come from, using the ALEX, HAPPY, HSCOLOR, and GHC environment variables (set in the Dockerfiles) to find bootstrapping tools.
* parser: Suggest ImportQualifiedPost in prepositive import warningBen Gamari2020-08-131-0/+1
| | | | As suggested in #18545.
* Simple subsumptionwip/T17775Simon Peyton Jones2020-06-051-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch simplifies GHC to use simple subsumption. Ticket #17775 Implements GHC proposal #287 https://github.com/ghc-proposals/ghc-proposals/blob/master/ proposals/0287-simplify-subsumption.rst All the motivation is described there; I will not repeat it here. The implementation payload: * tcSubType and friends become noticably simpler, because it no longer uses eta-expansion when checking subsumption. * No deeplyInstantiate or deeplySkolemise That in turn means that some tests fail, by design; they can all be fixed by eta expansion. There is a list of such changes below. Implementing the patch led me into a variety of sticky corners, so the patch includes several othe changes, some quite significant: * I made String wired-in, so that "foo" :: String rather than "foo" :: [Char] This improves error messages, and fixes #15679 * The pattern match checker relies on knowing about in-scope equality constraints, andd adds them to the desugarer's environment using addTyCsDs. But the co_fn in a FunBind was missed, and for some reason simple-subsumption ends up with dictionaries there. So I added a call to addTyCsDs. This is really part of #18049. * I moved the ic_telescope field out of Implication and into ForAllSkol instead. This is a nice win; just expresses the code much better. * There was a bug in GHC.Tc.TyCl.Instance.tcDataFamInstHeader. We called checkDataKindSig inside tc_kind_sig, /before/ solveEqualities and zonking. Obviously wrong, easily fixed. * solveLocalEqualitiesX: there was a whole mess in here, around failing fast enough. I discovered a bad latent bug where we could successfully kind-check a type signature, and use it, but have unsolved constraints that could fill in coercion holes in that signature -- aargh. It's all explained in Note [Failure in local type signatures] in GHC.Tc.Solver. Much better now. * I fixed a serious bug in anonymous type holes. IN f :: Int -> (forall a. a -> _) -> Int that "_" should be a unification variable at the /outer/ level; it cannot be instantiated to 'a'. This was plain wrong. New fields mode_lvl and mode_holes in TcTyMode, and auxiliary data type GHC.Tc.Gen.HsType.HoleMode. This fixes #16292, but makes no progress towards the more ambitious #16082 * I got sucked into an enormous refactoring of the reporting of equality errors in GHC.Tc.Errors, especially in mkEqErr1 mkTyVarEqErr misMatchMsg misMatchMsgOrCND In particular, the very tricky mkExpectedActualMsg function is gone. It took me a full day. But the result is far easier to understand. (Still not easy!) This led to various minor improvements in error output, and an enormous number of test-case error wibbles. One particular point: for occurs-check errors I now just say Can't match 'a' against '[a]' rather than using the intimidating language of "occurs check". * Pretty-printing AbsBinds Tests review * Eta expansions T11305: one eta expansion T12082: one eta expansion (undefined) T13585a: one eta expansion T3102: one eta expansion T3692: two eta expansions (tricky) T2239: two eta expansions T16473: one eta determ004: two eta expansions (undefined) annfail06: two eta (undefined) T17923: four eta expansions (a strange program indeed!) tcrun035: one eta expansion * Ambiguity check at higher rank. Now that we have simple subsumption, a type like f :: (forall a. Eq a => Int) -> Int is no longer ambiguous, because we could write g :: (forall a. Eq a => Int) -> Int g = f and it'd typecheck just fine. But f's type is a bit suspicious, and we might want to consider making the ambiguity check do a check on each sub-term. Meanwhile, these tests are accepted, whereas they were previously rejected as ambiguous: T7220a T15438 T10503 T9222 * Some more interesting error message wibbles T13381: Fine: one error (Int ~ Exp Int) rather than two (Int ~ Exp Int, Exp Int ~ Int) T9834: Small change in error (improvement) T10619: Improved T2414: Small change, due to order of unification, fine T2534: A very simple case in which a change of unification order means we get tow unsolved constraints instead of one tc211: bizarre impredicative tests; just accept this for now Updates Cabal and haddock submodules. Metric Increase: T12150 T12234 T5837 haddock.base Metric Decrease: haddock.compiler haddock.Cabal haddock.base Merge note: This appears to break the `UnliftedNewtypesDifficultUnification` test. It has been marked as broken in the interest of merging. (cherry picked from commit 66b7b195cb3dce93ed5078b80bf568efae904cc5)
* testsuite: Fix -Wcompat-unqualified-imports issuesBen Gamari2020-02-084-0/+5
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* Fix typos, using Wikipedia list of common typosBrian Wignall2019-11-281-1/+1
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* Whitespace-sensitive bang patterns (#1087, #17162)wip/whitespace-and-lookaheadVladislav Zavialov2019-11-272-3/+5
| | | | | | | | | | | | | | | | | | 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.
* Whitespace forward compatibility for proposal #229Vladislav Zavialov2019-10-302-2/+2
| | | | | | | | GHC Proposal #229 changes the lexical rules of Haskell, which may require slight whitespace adjustments in certain cases. This patch changes formatting in a few places in GHC and its testsuite in a way that enables it to compile under the proposed rules.
* Implement the -XUnliftedNewtypes extension.Andrew Martin2019-06-142-3/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | GHC Proposal: 0013-unlifted-newtypes.rst Discussion: https://github.com/ghc-proposals/ghc-proposals/pull/98 Issues: #15219, #1311, #13595, #15883 Implementation Details: Note [Implementation of UnliftedNewtypes] Note [Unifying data family kinds] Note [Compulsory newtype unfolding] This patch introduces the -XUnliftedNewtypes extension. When this extension is enabled, GHC drops the restriction that the field in a newtype must be of kind (TYPE 'LiftedRep). This allows types like Int# and ByteArray# to be used in a newtype. Additionally, coerce is made levity-polymorphic so that it can be used with newtypes over unlifted types. The bulk of the changes are in TcTyClsDecls.hs. With -XUnliftedNewtypes, getInitialKind is more liberal, introducing a unification variable to return the kind (TYPE r0) rather than just returning (TYPE 'LiftedRep). When kind-checking a data constructor with kcConDecl, we attempt to unify the kind of a newtype with the kind of its field's type. When typechecking a data declaration with tcTyClDecl, we again perform a unification. See the implementation note for more on this. Co-authored-by: Richard Eisenberg <rae@richarde.dev>
* Implement ImportQualifiedPostShayne Fletcher2019-05-088-0/+43
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* Update Trac ticket URLs to point to GitLabRyan Scott2019-03-151-1/+1
| | | | | This moves all URL references to Trac tickets to their corresponding GitLab counterparts.
* testsuite: Use makefile_testBen Gamari2019-01-303-12/+12
| | | | | This eliminates most uses of run_command in the testsuite in favor of the more structured makefile_test.
* Revert "Batch merge"Ben Gamari2019-01-303-12/+12
| | | | This reverts commit 76c8fd674435a652c75a96c85abbf26f1f221876.
* Batch mergeBen Gamari2019-01-303-12/+12
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* Fix unused-import warningsDavid Eichmann2018-11-221-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch fixes a fairly long-standing bug (dating back to 2015) in RdrName.bestImport, namely commit 9376249b6b78610db055a10d05f6592d6bbbea2f Author: Simon Peyton Jones <simonpj@microsoft.com> Date: Wed Oct 28 17:16:55 2015 +0000 Fix unused-import stuff in a better way In that patch got the sense of the comparison back to front, and thereby failed to implement the unused-import rules described in Note [Choosing the best import declaration] in RdrName This led to Trac #13064 and #15393 Fixing this bug revealed a bunch of unused imports in libraries; the ones in the GHC repo are part of this commit. The two important changes are * Fix the bug in bestImport * Modified the rules by adding (a) in Note [Choosing the best import declaration] in RdrName Reason: the previosu rules made Trac #5211 go bad again. And the new rule (a) makes sense to me. In unravalling this I also ended up doing a few other things * Refactor RnNames.ImportDeclUsage to use a [GlobalRdrElt] for the things that are used, rather than [AvailInfo]. This is simpler and more direct. * Rename greParentName to greParent_maybe, to follow GHC naming conventions * Delete dead code RdrName.greUsedRdrName Bumps a few submodules. Reviewers: hvr, goldfire, bgamari, simonmar, jrtc27 Subscribers: rwbarton, carter Differential Revision: https://phabricator.haskell.org/D5312
* Fix trac #15702, as a followon to fix for #13704.Chris Smith2018-11-174-1/+13
| | | | | | | | | | | | | | | | | | Summary: The effect of this change is that -main-is changes the default export list for the main module, but does not apply the same change to non-main modules. This fixes some cases where -main-is was used to wrap a module that expected that default behavior (exporting `main`, even when that wasn't the main entry point name). Reviewers: mpickering, monoidal, bgamari Subscribers: rwbarton, carter GHC Trac Issues: #13704, #15702 Differential Revision: https://phabricator.haskell.org/D5322
* Fix for Trac #15611: Scope errors lie about what modules are imported.roland2018-11-041-1/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: For the error message: Not in scope X.Y Module X does not export Y No module named ‘X’ is imported: there are 2 cases, where we don't show the last "no module named is imported" line: 1. If the module X has been imported. 2. If the module X is the current module. There are 2 subcases: 2.1 If the unknown module name is in a input source file, then we can use the getModule function to get the current module name. 2.2 If the unknown module name has been entered by the user in GHCi, then the getModule function returns something like "interactive:Ghci1", and we have to check the current module in the last added entry of the HomePackageTable. Test Plan: make test TESTS="T15611a T15611b" Reviewers: monoidal, hvr, thomie, dfeuer, bgamari, DavidEichmann Reviewed By: monoidal, DavidEichmann Subscribers: rwbarton, carter GHC Trac Issues: #15611 Differential Revision: https://phabricator.haskell.org/D5284
* resolve T13704chessai2018-10-022-1/+4
| | | | | | | | | | | | | | | | | Summary: allow -main-is to change export list for default module header, allowing one to change the entry point to one's program. Test Plan: ./validate Reviewers: bgamari, nomeata, mpickering Reviewed By: mpickering Subscribers: mpickering, rwbarton, carter GHC Trac Issues: #13704 Differential Revision: https://phabricator.haskell.org/D5189
* Fix for #13862: Optional "-v" not allowed with :load in GHCiroland2018-09-162-2/+2
| | | | | | | | | | | | | | | Replace the error message `Use -v to see a list of the files searched for.` with `Use -v (or :set -v` in ghci) to see a list of the files searched for.` Reviewers: bgamari, monoidal, thomie, osa1 Subscribers: rwbarton, carter GHC Trac Issues: #13862 Differential Revision: https://phabricator.haskell.org/D5122
* Improve error message on un-satisfied importSimon Peyton Jones2018-07-252-4/+3
| | | | | | | | | | | | | | | | | | Consider import M( C( a,b,c ) ) where class C is defined as module M where class C x where a :: blah c :: blah Tnen (Trac #15413) we'd like to get an error message only about failing to import C( b ), not C( a,b,c ). This was fairly easy (and local) to do. Turned out that the existing tests mod81 and mod91 are adequate tests for the feature.
* Improved Valid Hole FitsMatthías Páll Gissurarson2018-05-301-4/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | I've changed the name from `Valid substitutions` to `Valid hole fits`, since "substitution" already has a well defined meaning within the theory. As part of this change, the flags and output is reanamed, with substitution turning into hole-fit in most cases. "hole fit" was already used internally in the code, it's clear and shouldn't cause any confusion. In this update, I've also reworked how we manage side-effects in the hole we are considering. This allows us to consider local bindings such as where clauses and arguments to functions, suggesting e.g. `a` for `head (x:xs) where head :: [a] -> a`. It also allows us to find suggestions such as `maximum` for holes of type `Ord a => a -> [a]`, and `max` when looking for a match for the hole in `g = foldl1 _`, where `g :: Ord a => [a] -> a`. We also show much improved output for refinement hole fits, and fixes #14990. We now show the correct type of the function, but we also now show what the arguments to the function should be e.g. `foldl1 (_ :: Integer -> Integer -> Integer)` when looking for `[Integer] -> Integer`. I've moved the bulk of the code from `TcErrors.hs` to a new file, `TcHoleErrors.hs`, since it was getting too big to not live on it's own. This addresses the considerations raised in #14969, and takes proper care to set the `tcLevel` of the variables to the right level before passing it to the simplifier. We now also zonk the suggestions properly, which improves the output of the refinement hole fits considerably. This also filters out suggestions from the `GHC.Err` module, since even though `error` and `undefined` are indeed valid hole fits, they are "trivial", and almost never useful to the user. We now find the hole fits using the proper manner, namely by solving nested implications. This entails that the givens are passed along using the implications the hole was nested in, which in turn should mean that there will be fewer weird bugs in the typed holes. I've also added a new sorting method (as suggested by SPJ) and sort by the size of the types needed to turn the hole fits into the type of the hole. This gives a reasonable approximation to relevance, and is much faster than the subsumption check. I've also added a flag to toggle whether to use this new sorting algorithm (as is done by default) or the subsumption algorithm. This fixes #14969 I've also added documentation for these new flags and update the documentation according to the new output. Reviewers: bgamari, goldfire Reviewed By: bgamari Subscribers: simonpj, rwbarton, thomie, carter GHC Trac Issues: #14969, #14990, #10946 Differential Revision: https://phabricator.haskell.org/D4444
* Track type variable scope more carefully.Richard Eisenberg2018-03-311-3/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The main job of this commit is to track more accurately the scope of tyvars introduced by user-written foralls. For example, it would be to have something like this: forall a. Int -> (forall k (b :: k). Proxy '[a, b]) -> Bool In that type, a's kind must be k, but k isn't in scope. We had a terrible way of doing this before (not worth repeating or describing here, but see the old tcImplicitTKBndrs and friends), but now we have a principled approach: make an Implication when kind-checking a forall. Doing so then hooks into the existing machinery for preventing skolem-escape, performing floating, etc. This also means that we bump the TcLevel whenever going into a forall. The new behavior is done in TcHsType.scopeTyVars, but see also TcHsType.tc{Im,Ex}plicitTKBndrs, which have undergone significant rewriting. There are several Notes near there to guide you. Of particular interest there is that Implication constraints can now have skolems that are out of order; this situation is reported in TcErrors. A major consequence of this is a slightly tweaked process for type- checking type declarations. The new Note [Use SigTvs in kind-checking pass] in TcTyClsDecls lays it out. The error message for dependent/should_fail/TypeSkolEscape has become noticeably worse. However, this is because the code in TcErrors goes to some length to preserve pre-8.0 error messages for kind errors. It's time to rip off that plaster and get rid of much of the kind-error-specific error messages. I tried this, and doing so led to a lovely error message for TypeSkolEscape. So: I'm accepting the error message quality regression for now, but will open up a new ticket to fix it, along with a larger error-message improvement I've been pondering. This applies also to dependent/should_fail/{BadTelescope2,T14066,T14066e}, polykinds/T11142. Other minor changes: - isUnliftedTypeKind didn't look for tuples and sums. It does now. - check_type used check_arg_type on both sides of an AppTy. But the left side of an AppTy isn't an arg, and this was causing a bad error message. I've changed it to use check_type on the left-hand side. - Some refactoring around when we print (TYPE blah) in error messages. The changes decrease the times when we do so, to good effect. Of course, this is still all controlled by -fprint-explicit-runtime-reps Fixes #14066 #14749 Test cases: dependent/should_compile/{T14066a,T14749}, dependent/should_fail/T14066{,c,d,e,f,g,h}
* typecheck: Consistently use pretty quotes in error messagesBen Gamari2017-11-272-2/+3
| | | | | | Subscribers: rwbarton, thomie, carter Differential Revision: https://phabricator.haskell.org/D4241
* typecheck: Clarify errors mentioned in #14385Ben Gamari2017-10-251-1/+1
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