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* Update testsuiteSylvain Henry2020-06-1749-99/+50
| | | | | | | | | | | | | | * 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
* Simple subsumptionwip/T17775Simon Peyton Jones2020-06-0531-190/+228
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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)
* Revert "Specify kind variables for inferred kinds in base."Ben Gamari2020-05-252-2/+2
| | | | | | | | As noted in !3132, this has rather severe knock-on consequences in user-code. We'll need to revisit this before merging something along these lines. This reverts commit 9749fe1223d182b1f8e7e4f7378df661c509f396.
* Specify kind variables for inferred kinds in base.Baldur Blöndal2020-05-082-2/+2
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* Refactor hole constraints.Richard Eisenberg2020-05-061-8/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Previously, holes (both expression holes / out of scope variables and partial-type-signature wildcards) were emitted as *constraints* via the CHoleCan constructor. While this worked fine for error reporting, there was a fair amount of faff in keeping these constraints in line. In particular, and unlike other constraints, we could never change a CHoleCan to become CNonCanonical. In addition: * the "predicate" of a CHoleCan constraint was really the type of the hole, which is not a predicate at all * type-level holes (partial type signature wildcards) carried evidence, which was never used * tcNormalise (used in the pattern-match checker) had to create a hole constraint just to extract it again; it was quite messy The new approach is to record holes directly in WantedConstraints. It flows much more nicely now. Along the way, I did some cleaning up of commentary in GHC.Tc.Errors.Hole, which I had a hard time understanding. This was instigated by a future patch that will refactor the way predicates are handled. The fact that CHoleCan's "predicate" wasn't really a predicate is incompatible with that future patch. No test case, because this is meant to be purely internal. It turns out that this change improves the performance of the pattern-match checker, likely because fewer constraints are sloshing about in tcNormalise. I have not investigated deeply, but an improvement is not a surprise here: ------------------------- Metric Decrease: PmSeriesG -------------------------
* Add a missing zonk in tcHsPartialTypeSimon Peyton Jones2020-04-183-0/+13
| | | | | | | | | | | | | I omitted a vital zonk when refactoring tcHsPartialType in commit 48fb3482f8cbc8a4b37161021e846105f980eed4 Author: Simon Peyton Jones <simonpj@microsoft.com> Date: Wed Jun 5 08:55:17 2019 +0100 Fix typechecking of partial type signatures This patch fixes it and adds commentary to explain why. Fixes #18008
* Fix #18052 by using pprPrefixOcc in more placesRyan Scott2020-04-151-25/+25
| | | | | This fixes several small oversights in the choice of pretty-printing function to use. Fixes #18052.
* Simplify treatment of heterogeneous equalityRichard Eisenberg2020-03-201-39/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | Previously, if we had a [W] (a :: k1) ~ (rhs :: k2), we would spit out a [D] k1 ~ k2 and part the W as irreducible, hoping for a unification. But we needn't do this. Instead, we now spit out a [W] co :: k2 ~ k1 and then use co to cast the rhs of the original Wanted. This means that we retain the connection between the spat-out constraint and the original. The problem with this new approach is that we cannot use the casted equality for substitution; it's too like wanteds-rewriting- wanteds. So, we forbid CTyEqCans that mention coercion holes. All the details are in Note [Equalities with incompatible kinds] in TcCanonical. There are a few knock-on effects, documented where they occur. While debugging an error in this patch, Simon and I ran into infelicities in how patterns and matches are printed; we made small improvements. This patch includes mitigations for #17828, which causes spurious pattern-match warnings. When #17828 is fixed, these lines should be removed.
* Always display inferred variables using bracesKrzysztof Gogolewski2020-02-1217-191/+199
| | | | | | | | | | | | | We now always show "forall {a}. T" for inferred variables, previously this was controlled by -fprint-explicit-foralls. This implements part 1 of https://github.com/ghc-proposals/ghc-proposals/pull/179. Part of GHC ticket #16320. Furthermore, when printing a levity restriction error, we now display the HsWrap of the expression. This lets users see the full elaboration with -fprint-typechecker-elaboration (see also #17670)
* Improve skolemisationSimon Peyton Jones2020-02-0117-23/+23
| | | | | | | | | This patch avoids skolemiseUnboundMetaTyVar making up a fresh Name when it doesn't need to. See Note [Skolemising and identity] Improves error messsages for partial type signatures.
* Don't zap to Any; error insteadRichard Eisenberg2020-01-121-33/+24
| | | | | | | | | This changes GHC's treatment of so-called Naughty Quantification Candidates to issue errors, instead of zapping to Any. Close #16775. No new test cases, because existing ones cover this well.
* Pretty-printing of the * kindVladislav Zavialov2019-12-052-10/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Before this patch, GHC always printed the * kind unparenthesized. This led to two issues: 1. Sometimes GHC printed invalid or incorrect code. For example, GHC would print: type F @* x = x when it meant to print: type F @(*) x = x In the former case, instead of a kind application we were getting a type operator (@*). 2. Sometimes GHC printed kinds that were correct but hard to read. Should Either * Int be read as Either (*) Int or as (*) Either Int ? This depends on whether -XStarIsType is enabled, but it would be easier if we didn't have to check for the flag when reading the code. We can solve both problems by assigning (*) a different precedence. Note that Haskell98 kinds are not affected: ((* -> *) -> *) -> * does NOT become (((*) -> (*)) -> (*)) -> (*) The parentheses are added when (*) is used in a function argument position: F * * * becomes F (*) (*) (*) F A * B becomes F A (*) B Proxy * becomes Proxy (*) a * -> * becomes a (*) -> *
* Whitespace-sensitive bang patterns (#1087, #17162)wip/whitespace-and-lookaheadVladislav Zavialov2019-11-272-16/+16
| | | | | | | | | | | | | | | | | | 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.
* Fix typosBrian Wignall2019-11-231-1/+1
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* Strip parentheses in expressions contexts in error messagesVladislav Zavialov2019-11-191-1/+1
| | | | This makes error messages a tad less noisy.
* Add Monad instances to `(,,) a b` and `(,,,) a b c`Fumiaki Kinoshita2019-10-041-1/+1
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* Use level numbers for generalisationRichard Eisenberg2019-09-191-5/+5
| | | | | | | | This fixes #15809, and is covered in Note [Use level numbers for quantification] in TcMType. This patch removes the "global tyvars" from the environment, a nice little win.
* Refactor kindGeneralize and friendsRichard Eisenberg2019-09-191-5/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit should have no change in behavior.(*) The observation was that Note [Recipe for checking a signature] says that every metavariable in a type-checked type must either (A) be generalized (B) be promoted (C) be zapped. Yet the code paths for doing these were all somewhat separate. This led to some steps being skipped. This commit shores this all up. The key innovation is TcHsType.kindGeneralizeSome, with appropriate commentary. This commit also sets the stage for #15809, by turning the WARNing about bad level-numbers in generalisation into an ASSERTion. The actual fix for #15809 will be in a separate commit. Other changes: * zonkPromoteType is now replaced by kindGeneralizeNone. This might have a small performance degradation, because zonkPromoteType zonked and promoted all at once. The new code path promotes first, and then zonks. * A call to kindGeneralizeNone was added in tcHsPartialSigType. I think this was a lurking bug, because it did not follow Note [Recipe for checking a signature]. I did not try to come up with an example showing the bug. This is the (*) above. Because of this change, there is an error message regression in partial-sigs/should_fail/T14040a. This problem isn't really a direct result of this refactoring, but is a symptom of something deeper. See #16775, which addresses the deeper problem. * I added a short-cut to quantifyTyVars, in case there's nothing to quantify. * There was a horribly-outdated Note that wasn't referred to. Gone now. * While poking around with T14040a, I discovered a small mistake in the Coercion.simplifyArgsWorker. Easy to fix, happily. * See new Note [Free vars in coercion hole] in TcMType. Previously, we were doing the wrong thing when looking at a coercion hole in the gather-candidates algorithm. Fixed now, with lengthy explanation. Metric Decrease: T14683
* Fix typechecking of partial type signaturesSimon Peyton Jones2019-06-198-4/+75
| | | | | | | | | | | | | | | | | | | | | | | | | | | Partial type sigs had grown hair. tcHsParialSigType was doing lots of unnecessary work, and tcInstSig was cloning it unnecessarily -- and the result didn't even work: #16728. This patch cleans it all up, described by TcHsType Note [Checking parital type signatures] I basically just deleted code... but very carefully! Some refactoring along the way * Distinguish more explicintly between "anonymous" wildcards "_" and "named" wildcards "_a". I changed the names of a number of functions to make this distinction much more apparent. The patch also revealed that the code in `TcExpr` that implements the special typing rule for `($)` was wrong. It called `getRuntimeRep` in a situation where where was no particular reason to suppose that the thing had kind `TYPE r`. This caused a crash in typecheck/should_run/T10846. The fix was easy, and actually simplifies the code in `TcExpr` quite a bit. Hooray.
* Bump ghc-prim's version where neededAlexandre2019-04-0148-48/+48
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* base: Remove `Monad(fail)` method and reexport `MonadFail(fail)` insteadHerbert Valerio Riedel2019-03-2248-49/+49
| | | | | | As per https://prime.haskell.org/wiki/Libraries/Proposals/MonadFail Coauthored-by: Ben Gamari <ben@well-typed.com>
* Add location to the extra-constraints wildcardSimon Peyton Jones2019-03-1614-29/+29
| | | | | | | The extra-constraints wildcard had lost its location (issue #16431). Happily this is easy to fix. Lots of error improvements.
* Update Trac ticket URLs to point to GitLabRyan Scott2019-03-153-3/+3
| | | | | This moves all URL references to Trac tickets to their corresponding GitLab counterparts.
* Ignore more version numbers in the testsuiteAlec Theriault2019-03-111-0/+2
| | | | | | | | | 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.
* Treat kind/type variables identically, demolish FKTVVladislav Zavialov2019-02-277-4/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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.
* Fail fast in solveLocalEqualitiesSimon Peyton Jones2019-02-142-33/+1
| | | | | | | | | | | | | | | | | | This patch makes us fail fast in TcSimplify.solveLocalEqualities, and in TcHsType.tc_hs_sig_type, if there are insoluble constraints. Previously we ploughed on even if there were insoluble constraints, leading to a cascade of hard-to-understand type errors. Failing eagerly is much better; hence a lot of testsuite error message changes. Eg if we have f :: [Maybe] -> blah f xs = e then trying typecheck 'f x = e' with an utterly bogus type is just asking for trouble. I can't quite remember what provoked me to make this change, but I think the error messages are notably improved, by removing confusing clutter and focusing on the real error.
* Visible kind applicationmynguyen2019-01-0346-222/+263
| | | | | | | | | | | | | | | | | | | | | | | Summary: This patch implements visible kind application (GHC Proposal 15/#12045), as well as #15360 and #15362. It also refactors unnamed wildcard handling, and requires that type equations in type families in Template Haskell be written with full type on lhs. PartialTypeSignatures are on and warnings are off automatically with visible kind application, just like in term-level. There are a few remaining issues with this patch, as documented in ticket #16082. Includes a submodule update for Haddock. Test Plan: Tests T12045a/b/c/TH1/TH2, T15362, T15592a Reviewers: simonpj, goldfire, bgamari, alanz, RyanGlScott, Iceland_jack Subscribers: ningning, Iceland_jack, RyanGlScott, int-index, rwbarton, mpickering, carter GHC Trac Issues: `#12045`, `#15362`, `#15592`, `#15788`, `#15793`, `#15795`, `#15797`, `#15799`, `#15801`, `#15807`, `#15816` Differential Revision: https://phabricator.haskell.org/D5229
* testsuite: Normalise away spurious differences in out-of-scope instancesBen Gamari2018-12-121-1/+1
| | | | | | | | | | | | | | | | | | | | This fixes a variety of testsuite failures with integer-simple of the form ``` --- typecheck/should_fail/tcfail072.run/tcfail072.stderr.normalised +++ typecheck/should_fail/tcfail072.run/tcfail072.comp.stderr.normalised @@ -12,7 +12,7 @@ -- Defined in ‘integer-<IMPL>-<VERSION>:GHC.Integer.Type’ instance Ord () -- Defined in ‘GHC.Classes’ ...plus 21 others - ...plus three instances involving out-of-scope types + ...plus two instances involving out-of-scope types (use -fprint-potential-instances to see them all) In the expression: g A In an equation for ‘g’: g (B _ _) = g A ``` In service of fixing #16043.
* Wibble to Taming the Kind Inference MonsterSimon Peyton Jones2018-12-077-18/+16
| | | | | | | | | | | | | | | | | | | 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.
* Taming the Kind Inference MonsterSimon Peyton Jones2018-11-298-27/+26
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | My original goal was (Trac #15809) to move towards using level numbers as the basis for deciding which type variables to generalise, rather than searching for the free varaibles of the environment. However it has turned into a truly major refactoring of the kind inference engine. Let's deal with the level-numbers part first: * Augment quantifyTyVars to calculate the type variables to quantify using level numbers, and compare the result with the existing approach. That is; no change in behaviour, just a WARNing if the two approaches give different answers. * To do this I had to get the level number right when calling quantifyTyVars, and this entailed a bit of care, especially in the code for kind-checking type declarations. * However, on the way I was able to eliminate or simplify a number of calls to solveEqualities. This work is incomplete: I'm not /using/ level numbers yet. When I subsequently get rid of any remaining WARNings in quantifyTyVars, that the level-number answers differ from the current answers, then I can rip out the current "free vars of the environment" stuff. Anyway, this led me into deep dive into kind inference for type and class declarations, which is an increasingly soggy part of GHC. Richard already did some good work recently in commit 5e45ad10ffca1ad175b10f6ef3327e1ed8ba25f3 Date: Thu Sep 13 09:56:02 2018 +0200 Finish fix for #14880. The real change that fixes the ticket is described in Note [Naughty quantification candidates] in TcMType. but I kept turning over stones. So this patch has ended up with a pretty significant refactoring of that code too. Kind inference for types and classes ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * Major refactoring in the way we generalise the inferred kind of a TyCon, in kcTyClGroup. Indeed, I made it into a new top-level function, generaliseTcTyCon. Plus a new Note to explain it Note [Inferring kinds for type declarations]. * We decided (Trac #15592) not to treat class type variables specially when dealing with Inferred/Specified/Required for associated types. That simplifies things quite a bit. I also rewrote Note [Required, Specified, and Inferred for types] * Major refactoring of the crucial function kcLHsQTyVars: I split it into kcLHsQTyVars_Cusk and kcLHsQTyVars_NonCusk because the two are really quite different. The CUSK case is almost entirely rewritten, and is much easier because of our new decision not to treat the class variables specially * I moved all the error checks from tcTyClTyVars (which was a bizarre place for it) into generaliseTcTyCon and/or the CUSK case of kcLHsQTyVars. Now tcTyClTyVars is extremely simple. * I got rid of all the all the subtleties in tcImplicitTKBndrs. Indeed now there is no difference between tcImplicitTKBndrs and kcImplicitTKBndrs; there is now a single bindImplicitTKBndrs. Same for kc/tcExplicitTKBndrs. None of them monkey with level numbers, nor build implication constraints. scopeTyVars is gone entirely, as is kcLHsQTyVarBndrs. It's vastly simpler. I found I could get rid of kcLHsQTyVarBndrs entirely, in favour of the bnew bindExplicitTKBndrs. Quantification ~~~~~~~~~~~~~~ * I now deal with the "naughty quantification candidates" of the previous patch in candidateQTyVars, rather than in quantifyTyVars; see Note [Naughty quantification candidates] in TcMType. I also killed off closeOverKindsCQTvs in favour of the same strategy that we use for tyCoVarsOfType: namely, close over kinds at the occurrences. And candidateQTyVars no longer needs a gbl_tvs argument. * Passing the ContextKind, rather than the expected kind itself, to tc_hs_sig_type_and_gen makes it easy to allocate the expected result kind (when we are in inference mode) at the right level. Type families ~~~~~~~~~~~~~~ * I did a major rewrite of the impenetrable tcFamTyPats. The result is vastly more comprehensible. * I got rid of kcDataDefn entirely, quite a big function. * I re-did the way that checkConsistentFamInst works, so that it allows alpha-renaming of invisible arguments. * The interaction of kind signatures and family instances is tricky. Type families: see Note [Apparently-nullary families] Data families: see Note [Result kind signature for a data family instance] and Note [Eta-reduction for data families] * The consistent instantation of an associated type family is tricky. See Note [Checking consistent instantiation] and Note [Matching in the consistent-instantation check] in TcTyClsDecls. It's now checked in TcTyClsDecls because that is when we have the relevant info to hand. * I got tired of the compromises in etaExpandFamInst, so I did the job properly by adding a field cab_eta_tvs to CoAxBranch. See Coercion.etaExpandCoAxBranch. tcInferApps and friends ~~~~~~~~~~~~~~~~~~~~~~~ * I got rid of the mysterious and horrible ClsInstInfo argument to tcInferApps, checkExpectedKindX, and various checkValid functions. It was horrible! * I got rid of [Type] result of tcInferApps. This list was used only in tcFamTyPats, when checking the LHS of a type instance; and if there is a cast in the middle, the list is meaningless. So I made tcInferApps simpler, and moved the complexity (not much) to tcInferApps. Result: tcInferApps is now pretty comprehensible again. * I refactored the many function in TcMType that instantiate skolems. Smaller things * I rejigged the error message in checkValidTelescope; I think it's quite a bit better now. * checkValidType was not rejecting constraints in a kind signature forall (a :: Eq b => blah). blah2 That led to further errors when we then do an ambiguity check. So I make checkValidType reject it more aggressively. * I killed off quantifyConDecl, instead calling kindGeneralize directly. * I fixed an outright bug in tyCoVarsOfImplic, where we were not colleting the tyvar of the kind of the skolems * Renamed ClsInstInfo to AssocInstInfo, and made it into its own data type * Some fiddling around with pretty-printing of family instances which was trickier than I thought. I wanted wildcards to print as plain "_" in user messages, although they each need a unique identity in the CoAxBranch. Some other oddments * Refactoring around the trace messages from reportUnsolved. * A bit of extra tc-tracing in TcHsSyn.commitFlexi This patch fixes a raft of bugs, and includes tests for them. * #14887 * #15740 * #15764 * #15789 * #15804 * #15817 * #15870 * #15874 * #15881
* Overhaul -fprint-explicit-kinds to use VKARyan Scott2018-11-222-10/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch changes the behavior of `-fprint-explicit-kinds` so that it displays kind argument using visible kind application. In other words, the flag now: 1. Prints instantiations of specified variables with `@(...)`. 2. Prints instantiations of inferred variables with `@{...}`. In addition, this patch removes the `Use -fprint-explicit-kinds to see the kind arguments` error message that often arises when a type mismatch occurs due to different kinds. Instead, whenever there is a kind mismatch, we now enable the `-fprint-explicit-kinds` flag locally to help cue to the programmer where the error lies. (See `Note [Kind arguments in error messages]` in `TcErrors`.) As a result, these funny `@{...}` things can now appear to the user even without turning on the `-fprint-explicit-kinds` flag explicitly, so I took the liberty of documenting them in the users' guide. Test Plan: ./validate Reviewers: goldfire, simonpj, bgamari Reviewed By: simonpj Subscribers: rwbarton, carter GHC Trac Issues: #15871 Differential Revision: https://phabricator.haskell.org/D5314
* Fix #15852 by eta expanding data family instance RHSes, tooRyan Scott2018-11-223-8/+8
| | | | | | | | | | | | | | | | | | | | | | When I defined `etaExpandFamInstLHS`, I blatantly forgot to eta expand the RHSes of data family instances. (Actually, I claimed that they didn't //need// to be eta expanded. I'm not sure what I was thinking.) This fixes the issue by changing `etaExpandFamInstLHS` to `etaExpandFamInst` and, well, making it actually eta expand the RHS. Test Plan: make test TEST=T15852 Reviewers: goldfire, bgamari Reviewed By: goldfire Subscribers: rwbarton, carter GHC Trac Issues: #15852 Differential Revision: https://phabricator.haskell.org/D5328
* Fix nasty bug in the type free-var finder, at lastSimon Peyton Jones2018-10-266-9/+9
| | | | | | | | | | | | | | | | | | | | | Consider the type forall k. b -> k where b :: k -> Type Here the 'k' in b's kind must be a different 'k' to the forall k, because 'b' is free in the expression. So we must return 'k' among the free vars returned from tyCoVarsOfType applied that type. But we weren't. This is an outright bug, although we don't have a program that fails because of it. It's easy to fix, too: see TyCoRep Note [Closing over free variable kinds] This fix has been in the pipeline for ages because it fell into the Trac #14880 swamp. But this patch nails it.
* Refactor the treatment of predicate typesSimon Peyton Jones2018-10-242-5/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Trac #15648 showed that GHC was a bit confused about the difference between the types for * Predicates * Coercions * Evidence (in the typechecker constraint solver) This patch cleans it up. See especially Type.hs Note [Types for coercions, predicates, and evidence] Particular changes * Coercion types (a ~# b) and (a ~#R b) are not predicate types (so isPredTy reports False for them) and are not implicitly instantiated by the type checker. This is a real change, but it consistently reflects that fact that (~#) and (~R#) really are different from predicates. * isCoercionType is renamed to isCoVarType * During type inference, simplifyInfer, we do /not/ want to infer a constraint (a ~# b), because that is no longer a predicate type. So we 'lift' it to (a ~ b). See TcType Note [Lift equality constaints when quantifying] * During type inference for pattern synonyms, we need to 'lift' provided constraints of type (a ~# b) to (a ~ b). See Note [Equality evidence in pattern synonyms] in PatSyn * But what about (forall a. Eq a => a ~# b)? Is that a predicate type? No -- it does not have kind Constraint. Is it an evidence type? Perhaps, but awkwardly so. In the end I decided NOT to make it an evidence type, and to ensure the the type inference engine never meets it. This made me /simplify/ the code in TcCanonical.makeSuperClasses; see TcCanonical Note [Equality superclasses in quantified constraints] Instead I moved the special treatment for primitive equality to TcInteract.doTopReactOther. See TcInteract Note [Looking up primitive equalities in quantified constraints] Also see Note [Evidence for quantified constraints] in Type. All this means I can have isEvVarType ty = isCoVarType ty || isPredTy ty which is nice. All in all, rather a lot of work for a small refactoring, but I think it's a real improvement.
* Improve output from -ddump-typesSimon Peyton Jones2018-10-2447-111/+15
| | | | | | | | | | | | | | | | | | This patch makes a number of improvements to the output generated by -ddump-types * Prints data constructor separately * Omits empty chunks of output I was driven initially by the unhelpful existing output for data constructors, but ended up doing some refactoring. Lots of error message wibbles, but nothing significant. Certainly no change in user behaviour. (NB: It is just possible that I have failed to cleanly separate this patch from the next one, about isPredTy and friends.)
* Enable -Wcompat=error in the testsuiteVladislav Zavialov2018-10-154-13/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Enabling -Werror=compat in the testsuite allows us to easily see the impact that a new warning has on code. It also means that in the period between adding the warning and making the actual breaking change, all new test cases that are being added to the testsuite will be forwards-compatible. This is good because it will make the actual breaking change contain less irrelevant testsuite updates. Things that -Wcompat warns about are things that are going to break in the future, so we can be proactive and keep our testsuite forwards-compatible. This patch consists of two main changes: * Add `TEST_HC_OPTS += -Werror=compat` to the testsuite configuration. * Fix all broken test cases. Test Plan: Validate Reviewers: hvr, goldfire, bgamari, simonpj, RyanGlScott Reviewed By: goldfire, RyanGlScott Subscribers: rwbarton, carter GHC Trac Issues: #15278 Differential Revision: https://phabricator.haskell.org/D5200
* Better -ddump-typesSimon Peyton Jones2018-10-047-12/+13
| | | | | | | | | | | The debug flag -ddump-types is supposed to show the type of Ids, and the kinds of type constructors. It was doing the former but not the latter -- instead it was using showTyTying, which is actually less helpful when debugging. This patch changes it to print the kind and roles of the thing. I also made -ddump-types show pattern synonyms
* Fix #15415 and simplify tcWildCardBindersVladislav Zavialov2018-08-015-0/+52
| | | | | | | | | | | | | | Test Plan: Validate Reviewers: goldfire, simonpj, bgamari Reviewed By: simonpj Subscribers: RyanGlScott, rwbarton, thomie, carter GHC Trac Issues: #15415 Differential Revision: https://phabricator.haskell.org/D5022
* Do not imply NoStarIsType by TypeOperators/TypeInTypeVladislav Zavialov2018-07-163-40/+30
| | | | | | | | | | | | | | | | | | | | | | Implementation of the "Embrace TypeInType" proposal was done according to the spec, which specified that TypeOperators must imply NoStarIsType. This implication was meant to prevent breakage and to be removed in 2 releases. However, compiling head.hackage has shown that this implication only magnified the breakage, so there is no reason to have it in the first place. To remain in compliance with the three-release policy, we add a workaround to define the (*) type operator even when -XStarIsType is on. Test Plan: ./validate Reviewers: bgamari, RyanGlScott, goldfire, phadej, hvr Reviewed By: bgamari, RyanGlScott Subscribers: harpocrates, rwbarton, thomie, carter Differential Revision: https://phabricator.haskell.org/D4865
* Use IfaceAppArgs to store an IfaceAppTy's argumentsRyan Scott2018-07-111-6/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: Currently, an `IfaceAppTy` has no way to tell whether its argument is visible or not, so it simply treats all arguments as visible, leading to #15330. We already have a solution for this problem in the form of the `IfaceTcArgs` data structure, used by `IfaceTyConApp` to represent the arguments to a type constructor. Therefore, it makes sense to reuse this machinery for `IfaceAppTy`, so this patch does just that. This patch: 1. Renames `IfaceTcArgs` to `IfaceAppArgs` to reflect its more general purpose. 2. Changes the second field of `IfaceAppTy` from `IfaceType` to `IfaceAppArgs`, and propagates the necessary changes through. In particular, pretty-printing an `IfaceAppTy` now goes through the `IfaceAppArgs` pretty-printer, which correctly displays arguments as visible or not for free, fixing #15330. 3. Changes `toIfaceTypeX` and related functions so that when converting an `AppTy` to an `IfaceAppTy`, it flattens as many argument `AppTy`s as possible, and then converts those arguments into an `IfaceAppArgs` list, using the kind of the function `Type` as a guide. (Doing so minimizes the number of times we need to call `typeKind`, which is more expensive that finding the kind of a `TyCon`.) Test Plan: make test TEST=T15330 Reviewers: goldfire, simonpj, bgamari Reviewed By: simonpj Subscribers: rwbarton, thomie, carter GHC Trac Issues: #15330 Differential Revision: https://phabricator.haskell.org/D4938
* Unwrap casts before checking vars in eager unifierRichard Eisenberg2018-07-103-44/+53
| | | | | | | | | | | Previously, checking whether (tv |> co) ~ (tv |> co) got deferred, because we looked for vars before stripping casts. (The left type would get stripped, and then tv ~ (tv |> co) would scare the occurs- checker.) This opportunity for improvement presented itself in other work. This is just an optimization. Some programs can now report more errors simultaneously.
* Refactor validity checking for constraintsSimon Peyton Jones2018-07-051-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There are several changes here. * TcInteract has gotten too big, so I moved all the class-instance matching out of TcInteract into a new module ClsInst. It parallels the FamInst module. The main export of ClsInst is matchGlobalInst. This now works in TcM not TcS. * A big reason to make matchGlobalInst work in TcM is that we can then use it from TcValidity.checkSimplifiableClassConstraint. That extends checkSimplifiableClassConstraint to work uniformly for built-in instances, which means that we now get a warning if we have givens (Typeable x, KnownNat n); see Trac #15322. * This change also made me refactor LookupInstResult, in particular by adding the InstanceWhat field. I also changed the name of the type to ClsInstResult. Then instead of matchGlobalInst reporting a staging error (which is inappropriate for the call from TcValidity), we can do so in TcInteract.checkInstanceOK. * In TcValidity, we now check quantified constraints for termination. For example, this signature should be rejected: f :: (forall a. Eq (m a) => Eq (m a)) => blah as discussed in Trac #15316. The main change here is that TcValidity.check_pred_help now uses classifyPredType, and has a case for ForAllPred which it didn't before. This had knock-on refactoring effects in TcValidity.
* Built-in Natural literals in CoreSylvain Henry2018-06-151-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add support for built-in Natural literals in Core. - Replace MachInt,MachWord, LitInteger, etc. with a single LitNumber constructor with a LitNumType field - Support built-in Natural literals - Add desugar warning for negative literals - Move Maybe(..) from GHC.Base to GHC.Maybe for module dependency reasons This patch introduces only a few rules for Natural literals (compared to Integer's rules). Factorization of the built-in rules for numeric literals will be done in another patch as this one is already big to review. Test Plan: validate test build with integer-simple Reviewers: hvr, bgamari, goldfire, Bodigrim, simonmar Reviewed By: bgamari Subscribers: phadej, simonpj, RyanGlScott, carter, hsyl20, rwbarton, thomie GHC Trac Issues: #14170, #14465 Differential Revision: https://phabricator.haskell.org/D4212
* Embrace -XTypeInType, add -XStarIsTypeVladislav Zavialov2018-06-1411-75/+89
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: Implement the "Embrace Type :: Type" GHC proposal, .../ghc-proposals/blob/master/proposals/0020-no-type-in-type.rst GHC 8.0 included a major change to GHC's type system: the Type :: Type axiom. Though casual users were protected from this by hiding its features behind the -XTypeInType extension, all programs written in GHC 8+ have the axiom behind the scenes. In order to preserve backward compatibility, various legacy features were left unchanged. For example, with -XDataKinds but not -XTypeInType, GADTs could not be used in types. Now these restrictions are lifted and -XTypeInType becomes a redundant flag that will be eventually deprecated. * Incorporate the features currently in -XTypeInType into the -XPolyKinds and -XDataKinds extensions. * Introduce a new extension -XStarIsType to control how to parse * in code and whether to print it in error messages. Test Plan: Validate Reviewers: goldfire, hvr, bgamari, alanz, simonpj Reviewed By: goldfire, simonpj Subscribers: rwbarton, thomie, mpickering, carter GHC Trac Issues: #15195 Differential Revision: https://phabricator.haskell.org/D4748
* 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
* Clean up the conflicting data family instances error messageRyan Scott2018-05-242-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: The way we were pretty-printing conflicting data family instances in an error message was far from ideal: 1. If a data type had no constructors, it would print an equals sign with nothing to the right of it. 2. It would try to print GADTs using Haskell98 syntax. 3. It eta-reduced away some type variables from the LHS. This patch addresses these three issues: 1. We no longer print constructors at all in this error message. There's really no reason to do so in the first place, since duplicate data family instances always conflict, regardless of their constructors. 2. Since we no longer print constructors, we no longer have to worry about whether we're using GADT or Haskell98 syntax. 3. I've put in a fix to ensure that type variables are no longer eta-reduced away from the LHS. Test Plan: make test TEST=T14179 Reviewers: goldfire, bgamari Reviewed By: bgamari Subscribers: rwbarton, thomie, carter GHC Trac Issues: #14179 Differential Revision: https://phabricator.haskell.org/D4711
* ghc-prim: Bump versionBen Gamari2018-05-2048-48/+48
| | | | | | | | | | | | | unpackClosure#'s behavior and type has changed. This caused a CPP guard in the new ghc-heap package to fail when bootstrapping with GHC 8.4. Test Plan: Validate bootstrapping with GHC 8.4 Reviewers: RyanGlScott Subscribers: rwbarton, thomie, carter Differential Revision: https://phabricator.haskell.org/D4716
* Another batch of './validation --slow' tweaksAlp Mestanogullari2018-05-201-1/+10
| | | | | | | | | | | | | | | | | | | | | | This finally gets us to a green ./validate --slow on linux for a ghc checkout from the beginning of this week, see https://circleci.com/gh/ghc/ghc/4739 This is hopefully the final (or second to final) patch to address #14890. Test Plan: ./validate --slow Reviewers: bgamari, hvr, simonmar Reviewed By: bgamari Subscribers: rwbarton, thomie, carter GHC Trac Issues: #14890 Differential Revision: https://phabricator.haskell.org/D4712
* Orient TyVar/TyVar equalities with deepest on the leftSimon Peyton Jones2018-05-181-11/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Trac #15009 showed that, for Given TyVar/TyVar equalities, we really want to orient them with the deepest-bound skolem on the left. As it happens, we also want to do the same for Wanteds, but for a different reason (more likely to be touchable). Either way, deepest wins: see TcUnify Note [Deeper level on the left]. This observation led me to some significant changes: * A SkolemTv already had a TcLevel, but the level wasn't really being used. Now it is! * I updated added invariant (SkolInf) to TcType Note [TcLevel and untouchable type variables], documenting that the level number of all the ic_skols should be the same as the ic_tclvl of the implication * FlatSkolTvs and FlatMetaTvs previously had a dummy level-number of zero, which messed the scheme up. Now they get a level number the same way as all other TcTyVars, instead of being a special case. * To make sure that FlatSkolTvs and FlatMetaTvs are untouchable (which was previously done via their magic zero level) isTouchableMetaTyVar just tests for those two cases. * TcUnify.swapOverTyVars is the crucial orientation function; see the new Note [TyVar/TyVar orientation]. I completely rewrote this function, and it's now much much easier to understand. I ended up doing some related refactoring, of course * I noticed that tcImplicitTKBndrsX and tcExplicitTKBndrsX were doing a lot of useless work in the case where there are no skolems; I added a fast-patch * Elminate the un-used tcExplicitTKBndrsSig; and thereby get rid of the higher-order parameter to tcExpliciTKBndrsX. * Replace TcHsType.emitTvImplication with TcUnify.checkTvConstraints, by analogy with TcUnify.checkConstraints. * Inline TcUnify.buildImplication into its only call-site in TcUnify.checkConstraints * TcS.buildImplication becomes TcS.CheckConstraintsTcS, with a simpler API * Now that we have NoEvBindsVar we have no need of termEvidenceAllowed; nuke the latter, adding Note [No evidence bindings] to TcEvidence.
* Add regression tests for #11515 and #12563Ryan Scott2018-05-183-0/+14
| | | | | Happily, both of these issues appear to have been fixed in GHC 8.2. Let's add regression tests for them to ensure that they stay fixed.
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