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* Update testsuiteSylvain Henry2020-06-172-3/+3
| | | | | | | | | | | | | | * support detection of slow ghc-bignum backend (to replace the detection of integer-simple use). There are still some test cases that the native backend doesn't handle efficiently enough. * remove tests for GMP only functions that have been removed from ghc-bignum * fix test results showing dependent packages (e.g. integer-gmp) or showing suggested instances * fix test using Integer/Natural API or showing internal names
* Simplify bindLHsTyVarBndrs and bindHsQTyVarswip/simply-bind-tyvarsRyan Scott2020-06-052-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Both `bindLHsTyVarBndrs` and `bindHsQTyVars` take two separate `Maybe` arguments, which I find terribly confusing. Thankfully, it's possible to remove one `Maybe` argument from each of these functions, which this patch accomplishes: * `bindHsQTyVars` takes a `Maybe SDoc` argument, which is `Just` if GHC should warn about any of the quantified type variables going unused. However, every call site uses `Nothing` in practice. This makes sense, since it doesn't really make sense to warn about unused type variables bound by an `LHsQTyVars`. For instance, you wouldn't warn about the `a` in `data Proxy a = Proxy` going unused. As a result, I simply remove this `Maybe SDoc` argument altogether. * `bindLHsTyVarBndrs` also takes a `Maybe SDoc` argument for the same reasons that `bindHsQTyVars` took one. To make things more confusing, however, `bindLHsTyVarBndrs` also takes a separate `HsDocContext` argument, which is pretty-printed (to an `SDoc`) in warnings and error messages. In practice, the `Maybe SDoc` and the `HsDocContext` often contain the same text. See the call sites for `bindLHsTyVarBndrs` in `rnFamInstEqn` and `rnConDecl`, for instance. There are only a handful of call sites where the text differs between the `Maybe SDoc` and `HsDocContext` arguments: * In `rnHsRuleDecl`, where the `Maybe SDoc` says "`In the rule`" and the `HsDocContext` says "`In the transformation rule`". * In `rnHsTyKi`/`rn_ty`, where the `Maybe SDoc` says "`In the type`" but the `HsDocContext` is inhereted from the surrounding context (e.g., if `rnHsTyKi` were called on a top-level type signature, the `HsDocContext` would be "`In the type signature`" instead) In both cases, warnings/error messages arguably _improve_ by unifying making the `Maybe SDoc`'s text match that of the `HsDocContext`. As a result, I decided to remove the `Maybe SDoc` argument to `bindLHsTyVarBndrs` entirely and simply reuse the text from the `HsDocContext`. (I decided to change the phrase "transformation rule" to "rewrite rule" while I was in the area.) The `Maybe SDoc` argument has one other purpose: signaling when to emit "`Unused quantified type variable`" warnings. To recover this functionality, I replaced the `Maybe SDoc` argument with a boolean-like `WarnUnusedForalls` argument. The only `bindLHsTyVarBndrs` call site that chooses _not_ to emit these warnings in `bindHsQTyVars`.
* Simple subsumptionwip/T17775Simon Peyton Jones2020-06-051-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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)
* Fix #18145 and also avoid needless work with implicit varsJohn Ericson2020-05-233-0/+24
| | | | | | | | | | | | - `forAllOrNothing` now is monadic, so we can trace whether we bind an explicit `forall` or not. - #18145 arose because the free vars calculation was needlessly complex. It is now greatly simplified. - Replaced some other implicit var code with `filterFreeVarsToBind`. Co-authored-by: Ryan Scott <ryan.gl.scott@gmail.com>
* Handle single unused importJeff Happily2020-05-134-4/+4
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* Re-quantify when generalising over rewrite rule typesRyan Scott2020-03-111-10/+0
| | | | | | | | | | | | | | | | | | | | | | Previously, `tcRules` would check for naughty quantification candidates (see `Note [Naughty quantification candidates]` in `TcMType`) when generalising over the type of a rewrite rule. This caused sensible-looking rewrite rules (like those in #17710) to be rejected. A more permissing (and easier-to-implement) approach is to do what is described in `Note [Generalising in tcTyFamInstEqnGuts]` in `TcTyClsDecls`: just re-quantify all the type variable binders, regardless of the order in which the user specified them. After all, the notion of type variable specificity has no real meaning in rewrite rules, since one cannot "visibly apply" a rewrite rule. I have written up this wisdom in `Note [Re-quantify type variables in rules]` in `TcRules`. As a result of this patch, compiling the `ExplicitForAllRules1` test case now generates one fewer warning than it used to. As far as I can tell, this is benign, since the thing that the disappearing warning talked about was also mentioned in an entirely separate warning. Fixes #17710.
* Fix #17832: Weird handling of exports named main in 8.10-rc1Roland Senn2020-02-204-0/+10
| | | | | | | Switching from `lookupGlobalOccRn_maybe` to `lookupInfoOccRn` to check whether a `main` function is in scope. Unfortunately `lookupGlobalOccRn_maybe` complains if there are multiple `main` functions in scope.
* Fix unboxed tuple size limit (#17837)Joshua Price2020-02-182-0/+47
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* Introduce -Wcompat-unqualified-importsBen Gamari2020-02-087-0/+37
| | | | | | | | | | | | | 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
* testsuite: Fix -Wcompat-unqualified-imports issuesBen Gamari2020-02-0812-8/+19
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* Print Core type applications with no whitespace after @ (#17643)Ryan Scott2020-01-081-4/+4
| | | | | | | | | | | This brings the pretty-printer for Core in line with how visible type applications are normally printed: namely, with no whitespace after the `@` character (i.e., `f @a` instead of `f @ a`). While I'm in town, I also give the same treatment to type abstractions (i.e., `\(@a)` instead of `\(@ a)`) and coercion applications (i.e., `f @~x` instead of `f @~ x`). Fixes #17643.
* Fix typos, via a Levenshtein-style correctorBrian Wignall2020-01-044-4/+4
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* lookupBindGroupOcc: recommend names in the same namespace (#17593)Ryan Scott2019-12-203-0/+17
| | | | | | | | | | | Previously, `lookupBindGroupOcc`'s error message would recommend all similar names in scope, regardless of whether they were type constructors, data constructors, or functions, leading to the confusion witnessed in #17593. This is easily fixed by only recommending names in the same namespace, using the `nameSpacesRelated` function. Fixes #17593.
* Whitespace-sensitive bang patterns (#1087, #17162)wip/whitespace-and-lookaheadVladislav Zavialov2019-11-274-5/+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.
* Improve SPECIALIZE pragma error messages (Fixes #12126)Alina Banerjee2019-11-101-1/+1
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* testsuite: Make ExplicitForAllRules1 more robustBen Gamari2019-11-012-11/+15
| | | | Previously the test relied on `id` not inlining. Fix this.
* Whitespace forward compatibility for proposal #229Vladislav Zavialov2019-10-301-1/+1
| | | | | | | | 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.
* Improve documentation around empty tuples/listsRichard Eisenberg2019-10-031-1/+1
| | | | | | | | | | | | | | This patch also changes the way we handle empty lists, simplifying them somewhat. See Note [Empty lists]. Previously, we had to special-case empty lists in the type-checker. Now no more! Finally, this patch improves some documentation around the ir_inst field used in the type-checker. This breaks a test case, but I really think the problem is #17251, not really related to this patch. Test case: typecheck/should_compile/T13680
* Standalone kind signatures (#16794)wip/top-level-kind-signaturesVladislav Zavialov2019-09-251-15/+33
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implements GHC Proposal #54: .../ghc-proposals/blob/master/proposals/0054-kind-signatures.rst With this patch, a type constructor can now be given an explicit standalone kind signature: {-# LANGUAGE StandaloneKindSignatures #-} type Functor :: (Type -> Type) -> Constraint class Functor f where fmap :: (a -> b) -> f a -> f b This is a replacement for CUSKs (complete user-specified kind signatures), which are now scheduled for deprecation. User-facing changes ------------------- * A new extension flag has been added, -XStandaloneKindSignatures, which implies -XNoCUSKs. * There is a new syntactic construct, a standalone kind signature: type <name> :: <kind> Declarations of data types, classes, data families, type families, and type synonyms may be accompanied by a standalone kind signature. * A standalone kind signature enables polymorphic recursion in types, just like a function type signature enables polymorphic recursion in terms. This obviates the need for CUSKs. * TemplateHaskell AST has been extended with 'KiSigD' to represent standalone kind signatures. * GHCi :info command now prints the kind signature of type constructors: ghci> :info Functor type Functor :: (Type -> Type) -> Constraint ... Limitations ----------- * 'forall'-bound type variables of a standalone kind signature do not scope over the declaration body, even if the -XScopedTypeVariables is enabled. See #16635 and #16734. * Wildcards are not allowed in standalone kind signatures, as partial signatures do not allow for polymorphic recursion. * Associated types may not be given an explicit standalone kind signature. Instead, they are assumed to have a CUSK if the parent class has a standalone kind signature and regardless of the -XCUSKs flag. * Standalone kind signatures do not support multiple names at the moment: type T1, T2 :: Type -> Type -- rejected type T1 = Maybe type T2 = Either String See #16754. * Creative use of equality constraints in standalone kind signatures may lead to GHC panics: type C :: forall (a :: Type) -> a ~ Int => Constraint class C a where f :: C a => a -> Int See #16758. Implementation notes -------------------- * The heart of this patch is the 'kcDeclHeader' function, which is used to kind-check a declaration header against its standalone kind signature. It does so in two rounds: 1. check user-written binders 2. instantiate invisible binders a la 'checkExpectedKind' * 'kcTyClGroup' now partitions declarations into declarations with a standalone kind signature or a CUSK (kinded_decls) and declarations without either (kindless_decls): * 'kinded_decls' are kind-checked with 'checkInitialKinds' * 'kindless_decls' are kind-checked with 'getInitialKinds' * DerivInfo has been extended with a new field: di_scoped_tvs :: ![(Name,TyVar)] These variables must be added to the context in case the deriving clause references tcTyConScopedTyVars. See #16731.
* Expunge #ifdef and #ifndef from the codebaseJohn Ericson2019-07-141-1/+1
| | | | | | | | These are unexploded minds as far as the linter is concerned. I don't want to hit in my MRs by mistake! I did this with `sed`, and then rolled back some changes in the docs, config.guess, and the linter itself.
* Add regression test for old panic on inlining undeclared identifier (#495)Kevin Buhr2019-07-113-0/+15
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* Implement the -XUnliftedNewtypes extension.Andrew Martin2019-06-141-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* Do not report error if Name in pragma is unboundnineonine2019-06-093-0/+10
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* Add a regression test for #14548Vladislav Zavialov2019-05-083-0/+28
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* Suggest only local candidates from global envWojciech Baranowski2019-04-292-4/+7
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* rename: hadle type signatures with typosWojciech Baranowski2019-04-293-0/+31
| | | | | | | When encountering type signatures for unknown names, suggest similar alternatives. This fixes issue #16504
* base: Remove `Monad(fail)` method and reexport `MonadFail(fail)` insteadHerbert Valerio Riedel2019-03-221-1/+1
| | | | | | As per https://prime.haskell.org/wiki/Libraries/Proposals/MonadFail Coauthored-by: Ben Gamari <ben@well-typed.com>
* Update Trac ticket URLs to point to GitLabRyan Scott2019-03-1524-24/+24
| | | | | This moves all URL references to Trac tickets to their corresponding GitLab counterparts.
* Ignore more version numbers in the testsuiteAlec Theriault2019-03-111-1/+1
| | | | | | | | | Prevents some tests from failing just due to mismatched version numbers. These version numbers shouldn't cause tests to fail, especially since we *expect* them to be regularly incremented. The motivation for this particular set of changes came from the changes that came along with the `base` version bump in 8f19ecc95fbaf2cc977531d721085d8441dc09b7.
* Fix #13839: GHCi warnings do not respect the default module headerwip/magic-carpet-rideRoland Senn2019-03-089-0/+48
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* Fix #16385 by appending _maybe to a use of lookupGlobalOccRyan Scott2019-03-063-0/+14
| | | | | | | | | `instance forall c. c` claimed that `c` was out of scope because the renamer was invoking `lookupGlobalOcc` on `c` (in `RnNames.getLocalNonValBinders`) without binding `c` first. To avoid this, this patch changes GHC to invoke `lookupGlobalOcc_maybe` on `c` instead, and if that returns `Nothing`, then bail out, resulting in a better error message.
* Fix warnings and fatal parsing errorsVladislav Zavialov2019-02-171-0/+10
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* 'forall' always a keyword, plus the dot type operatorVladislav Zavialov2019-02-152-6/+8
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* Implement -Wredundant-record-wildcards and -Wunused-record-wildcardsMatthew Pickering2019-02-146-1/+92
| | | | | | | | | -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`.
* testsuite: Use makefile_testBen Gamari2019-01-303-14/+11
| | | | | This eliminates most uses of run_command in the testsuite in favor of the more structured makefile_test.
* Revert "Batch merge"Ben Gamari2019-01-303-11/+14
| | | | This reverts commit 76c8fd674435a652c75a96c85abbf26f1f221876.
* Batch mergeBen Gamari2019-01-303-14/+11
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* Fix #16116 by removing badAssocRhsRyan Scott2019-01-155-1/+20
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* Fix #16114 by adding a validity check to rnClsInstDeclRyan Scott2019-01-154-14/+15
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* Add -Wmissing-deriving-strategieschessai2019-01-067-0/+42
| | | | | | | | | | | | | | | 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
* testsuite: Fix a variety of issues when building with integer-simpleBen Gamari2018-12-241-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | * Mark arith011 as broken with integer-simple As noted in #16091, arith011 fails when run against integer-simple with a "divide by zero" exception. This suggests that integer-gmp and integer-simple are handling division by zero differently. * This also fixes broken_without_gmp; the lack of types made the previous failure silent, sadly. Improves situation of #16043. * Mark several tests implicitly depending upon integer-gmp as broken with integer-simple. These expect to see Core coming from integer-gmp, which breaks with integer-simple. * Increase runtime timeout multiplier of T11627a with integer-simple I previously saw that T11627a timed out in all profiling ways when run against integer-simple. I suspect this is due to integer-simple's rather verbose heap representation. Let's see whether increasing the runtime timeout helps. Fixes test for #11627. This is all in service of fixing #16043.
* Fix #16002 by moving a validity check to the renamerRyan Scott2018-12-203-0/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: The validity check which rejected things like: ```lang=haskell type family B x where A x = x ``` Used to live in the typechecker. But it turns out that this validity check was //only// being run on closed type families without CUSKs! This meant that GHC would silently accept something like this: ```lang=haskell type family B (x :: *) :: * where A x = x ``` This patch fixes the issue by moving this validity check to the renamer, where we can be sure that the check will //always// be run. Test Plan: make test TEST=T16002 Reviewers: simonpj, bgamari Reviewed By: simonpj Subscribers: goldfire, rwbarton, carter GHC Trac Issues: #16002 Differential Revision: https://phabricator.haskell.org/D5420
* Misleading msg with qualified imports "No module named X imported"Roland Senn2018-12-113-0/+6
| | | | | | | | | | | | | | | | | | | | To check whether a given module has been imported, we do the following: From the list of all qualified names we extract the distinct module names to a list of module names. Then we check whether the given module name is in this list of module names. Test Plan: make test TEST=T14225 Reviewers: mpickering, hvr, monoidal, osa1, bgamari Reviewed By: bgamari Subscribers: rwbarton, carter GHC Trac Issues: #14225 Differential Revision: https://phabricator.haskell.org/D5331
* Wibble to Taming the Kind Inference MonsterSimon Peyton Jones2018-12-071-1/+1
| | | | | | | | | | | | | | | | | | | I had allowed rename/should_fail/T15828 (Trac #15828) to regress a bit. The main payload of this patch is to fix that problem, at the cost of more contortions in checkConsistentFamInst. Oh well, at least they are highly localised. I also update the -ddump-types code in TcRnDriver to print out some more expicit information about each type constructor, thus instead of DF{3} :: forall k. * -> k -> * we get data family DF{3} :: forall k. * -> k -> * Remember, this is debug-printing only. This change is the reason that so many .stderr files change.
* Remove duplicates in -ddump-minimial-importsSimon Peyton Jones2018-12-054-1/+13
| | | | | | | | | | | | | | | | | | | | | This fixes Trac #15994. Previously RdrName.gresToAvailInfo assumed that the input list of GREs had no duplicates. I accidentally broke this precondition in this refactoring: commit 6353efc7694ba8ec86c091918e02595662169ae2 Date: Thu Nov 22 14:48:05 2018 -0500 Fix unused-import warnings This patch fixes a fairly long-standing bug (dating back to 2015) in RdrName.bestImport, namely (There was an ASSERT, but it's usually switched off in stage2. It tripped when I switched stage2 assertions on.) The fix is straightforward: account for dups in gresToAvailInfo.
* Accept T15828 test outputRyan Scott2018-11-291-6/+4
| | | | | This test output changed slightly due to commit 2257a86daa72db382eb927df12a718669d5491f8 (which is expected).
* Fix #15828, from `More explicit foralls`Matthew Yacavone2018-11-293-0/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: Fix a bug in commit 12eeb9 which permits the following: ``` class C a where type T a b instance C (Maybe a) where type forall a b. T (Maybe a) b = b ``` where instead, the user should write: ``` instance C (Maybe a) where type forall b. T (Maybe a) b = b ``` Update the users guide to discuss scoping of type variables in explicit foralls in type family instances. Test Plan: validate Reviewers: bgamari, goldfire, monoidal Reviewed By: goldfire Subscribers: monoidal, rwbarton, carter GHC Trac Issues: #15828 Differential Revision: https://phabricator.haskell.org/D5283
* Fix unused-import warningsDavid Eichmann2018-11-224-1/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 for Trac #15611: Scope errors lie about what modules are imported.roland2018-11-048-4/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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
* Actually fail in failIfEmitsConstraintsRichard Eisenberg2018-11-012-8/+0
| | | | | | | | | | | | The function TcHsType.failIfEmitsConstraints says that it fails. It even does so in its name. But it didn't! It *reported* constraints but didn't fail. Now it does. This is important in tcHsClsInstType; see the comments therein. This was discovered while looking at #15797, but that ticket requires visible kind application to exhibit the bug; the test case will come with the patch for #12045.
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