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* 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.
* Fix #15039 by pretty-printing equalities more systematicallyRyan Scott2018-05-169-1/+393
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | GHC previously had a handful of special cases for pretty-printing equalities in a more user-friendly manner, but they were far from comprehensive (see #15039 for an example of where this fell apart). This patch makes the pretty-printing of equalities much more systematic. I've adopted the approach laid out in https://ghc.haskell.org/trac/ghc/ticket/15039#comment:4, and updated `Note [Equality predicates in IfaceType]` accordingly. We are now more careful to respect the properties of the `-fprint-explicit-kinds` and `-fprint-equality-relations` flags, which led to some improvements in error message outputs. Along the way, I also tweaked the error-reporting machinery not to print out the type of a typed hole when the type is an unlifted equality, since it's kind (`TYPE ('TupleRep '[])`) was more confusing than anything. Test Plan: make test TEST="T15039a T15039b T15039c T15039d" Reviewers: simonpj, goldfire, bgamari Reviewed By: simonpj Subscribers: rwbarton, thomie, carter GHC Trac Issues: #15039 Differential Revision: https://phabricator.haskell.org/D4696
* Tidy up error suppressionSimon Peyton Jones2018-05-152-0/+24
| | | | | | | | | | | | | Trac #15152 showed that when a flag turned an error into a warning, we were still (alas) suppressing subequent errors; includign their essential addTcEvBind. That led (rightly) to a Lint error. This patch fixes it, and incidentally tidies up an ad-hoc special case of out-of-scope variables (see the old binding for 'out_of_scope_killer' in 'tryReporters'). No test, because the problem was only shown up when turning inaccessible code into a warning.
* Add 'addWordC#' PrimOpSebastian Graf2018-05-0548-48/+48
| | | | | | | | | | | | | | | | | | | This is mostly for congruence with 'subWordC#' and '{add,sub}IntC#'. I found 'plusWord2#' while implementing this, which both lacks documentation and has a slightly different specification than 'addWordC#', which means the generic implementation is unnecessarily complex. While I was at it, I also added lacking meta-information on PrimOps and refactored 'subWordC#'s generic implementation to be branchless. Reviewers: bgamari, simonmar, jrtc27, dfeuer Reviewed By: bgamari, dfeuer Subscribers: dfeuer, thomie, carter Differential Revision: https://phabricator.haskell.org/D4592
* Bump base to version 4.12.0.0Ryan Scott2018-04-1948-48/+48
| | | | | | | | | | | | | | | | Summary: Bumps several submodules. Test Plan: ./validate Reviewers: hvr, bgamari Reviewed By: bgamari Subscribers: thomie, carter GHC Trac Issues: #15018 Differential Revision: https://phabricator.haskell.org/D4609
* Bump version numbers: base-4.11.1.0, integer-gmp-1.0.2.0Ryan Scott2018-04-1348-96/+96
| | | | | | | | | | | | | | | | | | | | | This takes care of bumping the `base` and `integer-gmp` minor version numbers in anticipation of a GHC 8.4.2 release. While I was in town, I also filled in a `@since TODO` Haddock annotation for `powModSecInteger` in `integer-gmp` with `1.0.2.0`, and updated the changelog accordingly. Test Plan: ./validate Reviewers: hvr, goldfire, bgamari Reviewed By: bgamari Subscribers: thomie, carter GHC Trac Issues: #15025 Differential Revision: https://phabricator.haskell.org/D4586
* Track type variable scope more carefully.Richard Eisenberg2018-03-314-18/+47
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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}
* Allow PartialTypeSignatures in standalone deriving contextsRyan Scott2018-03-237-0/+51
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: At its core, this patch is a simple tweak that allows a user to write: ```lang=haskell deriving instance _ => Eq (Foo a) ``` Which is functionally equivalent to: ```lang=haskell data Foo a = ... deriving Eq ``` But with the added flexibility that `StandaloneDeriving` gives you (namely, the ability to use it anywhere, not just in the same module that `Foo` was declared in). This fixes #13324, and should hopefully address a use case brought up in #10607. Currently, only the use of a single, extra-constraints wildcard is permitted in a standalone deriving declaration. Any other wildcard is rejected, so things like `deriving instance (Eq a, _) => Eq (Foo a)` are currently forbidden. There are quite a few knock-on changes brought on by this change: * The `HsSyn` type used to represent standalone-derived instances was previously `LHsSigType`, which isn't sufficient to hold wildcard types. This needed to be changed to `LHsSigWcType` as a result. * Previously, `DerivContext` was a simple type synonym for `Maybe ThetaType`, under the assumption that you'd only ever be in the `Nothing` case if you were in a `deriving` clause. After this patch, that assumption no longer holds true, as you can also be in this situation with standalone deriving when an extra-constraints wildcard is used. As a result, I changed `DerivContext` to be a proper datatype that reflects the new wrinkle that this patch adds, and plumbed this through the relevant parts of `TcDeriv` and friends. * Relatedly, the error-reporting machinery in `TcErrors` also assumed that if you have any unsolved constraints in a derived instance, then you should be able to fix it by switching over to standalone deriving. This was always sound advice before, but with this new feature, it's possible to have unsolved constraints even when you're standalone-deriving something! To rectify this, I tweaked some constructors of `CtOrigin` a bit to reflect this new subtlety. This requires updating the Haddock submodule. See my fork at https://github.com/RyanGlScott/haddock/commit/067d52fd4be15a1842cbb05f42d9d482de0ad3a7 Test Plan: ./validate Reviewers: simonpj, goldfire, bgamari Reviewed By: simonpj Subscribers: goldfire, rwbarton, thomie, mpickering, carter GHC Trac Issues: #13324 Differential Revision: https://phabricator.haskell.org/D4383
* Simplify rnLHsInstTypeSimon Peyton Jones2018-03-052-3/+1
| | | | | | | | | | | This patch is preparatory for the main fix for Trac #13324 Here, we simplify rnLHsInstType so that it does not try to figure out the class name. This turns out to have a good (rather than bad) effect on error messages, and it prepares the way for the main event. Plus, less code!
* testsuite: Fix test output of T14715Ben Gamari2018-01-311-1/+10
| | | | | Arguably the warning should just be disabled for this test to eliminate unnecessary wiggle in the future.
* Move zonkWC to the right place in simplfyInferSimon Peyton Jones2018-01-313-0/+21
| | | | | | | runTcSWithEvBinds does some unification, so the zonkWC must be after, not before! Yikes. An outright bug. This fixes Trac #14715.
* Fix two more bugs in partial signaturesSimon Peyton Jones2018-01-097-4/+41
| | | | | | | | | | | | | | | | | | | | These were shown up by Trac #14643 Bug 1: if we had a single partial signature for two functions f, g :: forall a. _ -> a then we made two different SigTvs but with the sane Name. This was jolly confusing and ultimately led to deeply bogus results with Any's appearing in the resulting program. Yikes. Fix: clone the quantified variables in TcSigs.tcInstSig (as indeed its name suggests). Bug 2: we were not eliminating duplicate/superclass constraints in the partial signatures of a mutually recursive group. Easy to fix: we are already doing dup/superclass elim in TcSimplify.decideQuantification. So we move the partial-sig constraints there too.
* Fix floating of equalitiesSimon Peyton Jones2017-12-215-0/+119
| | | | | | | | | | | | | | | | | | | | | | | | | | | This rather subtle patch fixes Trac #14584. The problem was that we'd allowed a coercion, bound in a nested scope, to escape into an outer scope. The main changes are * TcSimplify.floatEqualities takes more care when floating equalities to make sure we don't float one out that mentions a locally-bound coercion. See Note [What prevents a constraint from floating] * TcSimplify.emitResidualConstraints (which emits the residual constraints in simplifyInfer) now avoids burying the constraints for escaping CoVars inside the implication constraint. * Since I had do to this stuff with CoVars, I moved the fancy footwork about not quantifying over CoVars from TcMType.quantifyTyVars to its caller TcSimplify.decideQuantifiedTyVars. I think its other callers don't need to worry about all this CoVar stuff. This turned out to be surprisigly tricky, and took me a solid day to get right. I think the result is reasonably neat, though, and well documented with Notes.
* Check for bogus quantified tyvars in partial type sigsSimon Peyton Jones2017-12-213-0/+20
| | | | | | | This fixes Trac #14479. Not difficult. See Note [Quantification and partial signatures] Wrinkle 4, in TcSimplify.
* Add regression test for #14040Ryan Scott2017-12-123-0/+83
| | | | | | | | This adds a regression test for the original program in #14040. This does not fix #14040 entirely, though, as the program in https://ghc.haskell.org/trac/ghc/ticket/14040#comment:2 still panics, so there is more work to be done there.
* Check quantification for partial type signatuesSimon Peyton Jones2017-11-273-0/+11
| | | | | | | | | | | Trac #14449 showed that we were failing to check that the quantified type variables of a partial type signature remained distinct. See Note [Quantified variables in partial type signatures] in TcBinds. A little refactoring along the way.
* Minimise provided dictionaries in pattern synonymsSimon Peyton Jones2017-11-085-50/+50
| | | | | | | | | | | Trac #14394 showed that it's possible to get redundant constraints in the inferred provided constraints of a pattern synonym. This patch removes the redundancy with mkMinimalBySCs. To do this I had to generalise the type of mkMinimalBySCs slightly. And, to reduce confusing reversal, I made it stable: it now returns its result in the same order as its input. That led to a raft of error message wibbles, mostly for the better.
* Bump ghc-prim to 0.5.2.0 and update changelogHerbert Valerio Riedel2017-10-1748-48/+48
| | | | | | | This is prompted by the addition of `compareByteArrays#` in e3ba26f8b49700b41ff4672f3f7f6a4e453acdcc NOTE: We may switch to synchronise `ghc-prim` with GHC's version at some point
* Improve type-error reportingSimon Peyton Jones2017-09-2511-61/+32
| | | | | | | | | | | This patch does two things: * When reporting a hole, we now include its kind if the kind is not just '*'. This addresses Trac #14265 * When reporting things like "'a' is a rigid type varaible bound by ...", this patch arranges to group the type variables together, so we don't repeat the "bound by..." stuff endlessly
* Deal with large extra-contraints wildcardsSimon Peyton Jones2017-09-253-0/+141
| | | | | | | | | | | | | | | For reasons explained in TcHsType Note [Extra-constraint holes in partial type signatures], if we had f :: (_) => blahs and the '_' was filled in by more than a 62-tuple of contraints, GHC crashed. The same Note explains the hacky solution I have adopted to evade this. Maybe there is some better way, but I couldn't see one that didn't involve a great deal of work. And the problem is a very narrow one! If the hack bites us we'll need to think again.
* Also show types that subsume a hole as valid substitutions for that hole.Matthías Páll Gissurarson2017-09-211-0/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This builds on the previous "Valid substitutions include..." functionality, but add subsumption checking as well, so that the suggested valid substitutions show not only exact matches, but also identifiers that fit the hole by virtue of subsuming the type of the hole (i.e. being more general than the type of the hole). Building on the previous example, in the given program ``` ps :: String -> IO () ps = putStrLn ps2 :: a -> IO () ps2 _ = putStrLn "hello, world" main :: IO () main = _ "hello, world" ``` The results would be something like ``` • Found hole: _ :: [Char] -> IO () • In the expression: _ In the expression: _ "hello, world" In an equation for ‘main’: main = _ "hello, world" • Relevant bindings include main :: IO () (bound at t1.hs:8:1) Valid substitutions include ps :: String -> IO () (defined at t1.hs:2:1) ps2 :: forall a. a -> IO () (defined at t1.hs:5:1) putStrLn :: String -> IO () (imported from ‘Prelude’ at t1.hs:1:1 (and originally defined in ‘System.IO’)) fail :: forall (m :: * -> *). Monad m => forall a. String -> m a (imported from ‘Prelude’ at t1.hs:1:1 (and originally defined in ‘GHC.Base’)) mempty :: forall a. Monoid a => a (imported from ‘Prelude’ at t1.hs:1:1 (and originally defined in ‘GHC.Base’)) print :: forall a. Show a => a -> IO () (imported from ‘Prelude’ at t1.hs:1:1 (and originally defined in ‘System.IO’)) (Some substitutions suppressed; use -fmax-valid-substitutions=N or -fno-max-valid-substitutions) ``` Signed-off-by: Matthías Páll Gissurarson <mpg@mpg.is> Modified according to suggestions from Simon PJ Accept tests that match the expectations, still a few to look better at Swithced to using tcLookup, after sit down with SPJ at ICFP. Implications are WIP. Now works with polymorphism and constraints! We still need to merge the latest master, before we can make a patch. Wrap the type of the hole, instead of implication shenanigans, As per SPJs suggestion, this is simpler and feels closer to what we actually want to do. Updated tests with the new implementation Remove debugging trace and update documentation Reviewers: austin, bgamari Reviewed By: bgamari Subscribers: RyanGlScott, rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D3930
* Bump base to 4.11.0.0Ben Gamari2017-09-2148-96/+96
| | | | | | | | | | Bumps numerous submodules. Reviewers: austin, hvr Subscribers: rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D3974
* Move NonEmpty definition into GHC.BaseHerbert Valerio Riedel2017-09-042-3/+3
| | | | | | This is a preparatory refactoring for Semigroup=>Monoid as it prevents a messy .hs-boot file which would interact inconveniently with the buildsystem...
* ghc-prim: Bump versionBen Gamari2017-07-2348-48/+48
| | | | (cherry picked from commit 8c5405f63c2de0c445ec171aab63c35786544b9e)
* Fix ungrammatical error messageRyan Scott2017-07-211-1/+1
| | | | | | | | | | | | Test Plan: If it builds, ship it Reviewers: austin, bgamari Reviewed By: bgamari Subscribers: rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D3772
* Some tidying up of type pretty-printingSimon Peyton Jones2017-05-263-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | Triggered by the changes in #13677, I ended up doing a bit of refactoring in type pretty-printing. * We were using TyOpPrec and FunPrec rather inconsitently, so I made it consisent. * That exposed the fact that we were a bit undecided about whether to print a + b -> c + d vs (a+b) -> (c+d) and similarly a ~ [b] => blah vs (a ~ [b]) => blah I decided to make TyOpPrec and FunPrec compare equal (in BasicTypes), so (->) is treated as equal precedence with other type operators, so you get the unambiguous forms above, even though they have more parens. We could readily reverse this decision. See Note [Type operator precedence] in BasicTypes * I fixed a bug in pretty-printing of HsType where some parens were omitted by mistake.
* Only pretty-print binders in closed type families with -fprint-explicit-forallsRyan Scott2017-04-251-1/+1
| | | | | | | | | | | | | | | | | | | Previously, we were unconditionally pretty-printing all type variable binders when pretty-printing closed type families (e.g., in the output of `:info` in GHCi). This threw me for a loop, so let's guard this behind the `-fprint-explicit-foralls` flag. Test Plan: make test TEST=T13420 Reviewers: goldfire, austin, bgamari Reviewed By: bgamari Subscribers: rwbarton, thomie GHC Trac Issues: #13420 Differential Revision: https://phabricator.haskell.org/D3497
* Yet more work on TcSimplify.simplifyInferSimon Peyton Jones2017-04-134-1/+55
| | | | | | | | | | | | | | | | | The proximate cause for this patch is Trac #13482, which pointed out further subtle interactions between - Inferring the most general type of a function - A partial type signature for that function That led me into /further/ changes to the shiny new stuff in TcSimplify.simplifyInfer, decideQuantification, decideMonoTyVars, and related functions. Happily, I was able to make some of it quite a bit simpler, notably the bit about promoting free tyvars. I'm happy with the result. Moreover I fixed Trac #13524 at the same time. Happy days.
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