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* Zonk the returned kind in tcFamTyPatsSimon Peyton Jones2021-01-302-0/+13
| | | | | | The motivation is given in Note [tcFamTyPats: zonking the result kind]. Fixes #19250 -- the fix is easy.
* Remove some redundant validity checks.Richard Eisenberg2021-01-273-5/+7
| | | | | | | | | | | | This commit also consolidates documentation in the user manual around UndecidableSuperClasses, UndecidableInstances, and FlexibleContexts. Close #19186. Close #19187. Test case: typecheck/should_compile/T19186, typecheck/should_fail/T19187{,a}
* Add instances for GHC.Tuple.SoloBen Gamari2021-01-271-1/+1
| | | | | | | | | | | | | | | The `Applicative` instance is the most important one (for array/vector/sequence indexing purposes), but it deserves all the usual ones. T12545 does silly 1% wibbles both ways, it seems, maybe depending on architecture. Metric Increase: T12545 Metric Decrease: T12545
* Never Anyify during kind inferenceRichard Eisenberg2021-01-093-1/+30
| | | | | | | | | See Note [Error on unconstrained meta-variables] in TcMType. Close #17301 Close #17567 Close #17562 Close #15474
* Clone the binders of a SAKS where necessarySimon Peyton Jones2020-12-244-0/+80
| | | | | | | | | | | | | | Given a kind signature type T :: forall k. k -> forall k. k -> blah data T a b = ... where those k's have the same unique (which is possible; see #19093) we were giving the tyConBinders in tycon T the same unique, which caused chaos. Fix is simple: ensure uniqueness when decomposing the kind signature. See GHC.Tc.Gen.HsType.zipBinders
* Reject dodgy scoping in associated family instance RHSesRyan Scott2020-12-172-1/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit e63518f5d6a93be111f9108c0990a1162f88d615 tried to push all of the logic of detecting out-of-scope type variables on the RHSes of associated type family instances to `GHC.Tc.Validity` by deleting a similar check in the renamer. Unfortunately, this commit went a little too far, as there are some corner cases that `GHC.Tc.Validity` doesn't detect. Consider this example: ```hs class C a where data D a instance forall a. C Int where data instance D Int = MkD a ``` If this program isn't rejected by the time it reaches the typechecker, then GHC will believe the `a` in `MkD a` is existentially quantified and accept it. This is almost surely not what the user wants! The simplest way to reject programs like this is to restore the old validity check in the renamer (search for `improperly_scoped` in `rnFamEqn`). Note that this is technically a breaking change, since the program in the `polykinds/T9574` test case (which previously compiled) will now be rejected: ```hs instance Funct ('KProxy :: KProxy o) where type Codomain 'KProxy = NatTr (Proxy :: o -> *) ``` This is because the `o` on the RHS will now be rejected for being out of scope. Luckily, this is simple to repair: ```hs instance Funct ('KProxy :: KProxy o) where type Codomain ('KProxy @o) = NatTr (Proxy :: o -> *) ``` All of the discussion is now a part of the revamped `Note [Renaming associated types]` in `GHC.Rename.Module`. A different design would be to make associated type family instances have completely separate scoping from the parent instance declaration, much like how associated type family default declarations work today. See the discussion beginning at https://gitlab.haskell.org/ghc/ghc/-/issues/18021#note_265729 for more on this point. This, however, would break even more programs that are accepted today and likely warrants a GHC proposal before going forward. In the meantime, this patch fixes the issue described in #18021 in the least invasive way possible. There are programs that are accepted today that will no longer be accepted after this patch, but they are arguably pathological programs, and they are simple to repair. Fixes #18021.
* Revert "Implement BoxedRep proposal"Ben Gamari2020-12-154-4/+6
| | | | | | This was inadvertently merged. This reverts commit 6c2eb2232b39ff4720fda0a4a009fb6afbc9dcea.
* Implement BoxedRep proposalAndrew Martin2020-12-144-6/+4
| | | | | | | | | | | | | | | | | | This implements the BoxedRep proposal, refacoring the `RuntimeRep` hierarchy from: ```haskell data RuntimeRep = LiftedPtrRep | UnliftedPtrRep | ... ``` to ```haskell data RuntimeRep = BoxedRep Levity | ... data Levity = Lifted | Unlifted ``` Closes #17526.
* Fix kind inference for data types. Again.Simon Peyton Jones2020-12-082-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch fixes several aspects of kind inference for data type declarations, especially data /instance/ declarations Specifically 1. In kcConDecls/kcConDecl make it clear that the tc_res_kind argument is only used in the H98 case; and in that case there is no result kind signature; and hence no need for the disgusting splitPiTys in kcConDecls (now thankfully gone). The GADT case is a bit different to before, and much nicer. This is what fixes #18891. See Note [kcConDecls: kind-checking data type decls] 2. Do not look at the constructor decls of a data/newtype instance in tcDataFamInstanceHeader. See GHC.Tc.TyCl.Instance Note [Kind inference for data family instances]. This was a new realisation that arose when doing (1) This causes a few knock-on effects in the tests suite, because we require more information than before in the instance /header/. New user-manual material about this in "Kind inference in data type declarations" and "Kind inference for data/newtype instance declarations". 3. Minor improvement in kcTyClDecl, combining GADT and H98 cases 4. Fix #14111 and #8707 by allowing the header of a data instance to affect kind inferece for the the data constructor signatures; as described at length in Note [GADT return types] in GHC.Tc.TyCl This led to a modest refactoring of the arguments (and argument order) of tcConDecl/tcConDecls. 5. Fix #19000 by inverting the sense of the test in new_locs in GHC.Tc.Solver.Canonical.canDecomposableTyConAppOK.
* Remove flattening variablesRichard Eisenberg2020-12-011-5/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch redesigns the flattener to simplify type family applications directly instead of using flattening meta-variables and skolems. The key new innovation is the CanEqLHS type and the new CEqCan constraint (Ct). A CanEqLHS is either a type variable or exactly-saturated type family application; either can now be rewritten using a CEqCan constraint in the inert set. Because the flattener no longer reduces all type family applications to variables, there was some performance degradation if a lengthy type family application is now flattened over and over (not making progress). To compensate, this patch contains some extra optimizations in the flattener, leading to a number of performance improvements. Close #18875. Close #18910. There are many extra parts of the compiler that had to be affected in writing this patch: * The family-application cache (formerly the flat-cache) sometimes stores coercions built from Given inerts. When these inerts get kicked out, we must kick out from the cache as well. (This was, I believe, true previously, but somehow never caused trouble.) Kicking out from the cache requires adding a filterTM function to TrieMap. * This patch obviates the need to distinguish "blocking" coercion holes from non-blocking ones (which, previously, arose from CFunEqCans). There is thus some simplification around coercion holes. * Extra commentary throughout parts of the code I read through, to preserve the knowledge I gained while working. * A change in the pure unifier around unifying skolems with other types. Unifying a skolem now leads to SurelyApart, not MaybeApart, as documented in Note [Binding when looking up instances] in GHC.Core.InstEnv. * Some more use of MCoercion where appropriate. * Previously, class-instance lookup automatically noticed that e.g. C Int was a "unifier" to a target [W] C (F Bool), because the F Bool was flattened to a variable. Now, a little more care must be taken around checking for unifying instances. * Previously, tcSplitTyConApp_maybe would split (Eq a => a). This is silly, because (=>) is not a tycon in Haskell. Fixed now, but there are some knock-on changes in e.g. TrieMap code and in the canonicaliser. * New function anyFreeVarsOf{Type,Co} to check whether a free variable satisfies a certain predicate. * Type synonyms now remember whether or not they are "forgetful"; a forgetful synonym drops at least one argument. This is useful when flattening; see flattenView. * The pattern-match completeness checker invokes the solver. This invocation might need to look through newtypes when checking representational equality. Thus, the desugarer needs to keep track of the in-scope variables to know what newtype constructors are in scope. I bet this bug was around before but never noticed. * Extra-constraints wildcards are no longer simplified before printing. See Note [Do not simplify ConstraintHoles] in GHC.Tc.Solver. * Whether or not there are Given equalities has become slightly subtler. See the new HasGivenEqs datatype. * Note [Type variable cycles in Givens] in GHC.Tc.Solver.Canonical explains a significant new wrinkle in the new approach. * See Note [What might match later?] in GHC.Tc.Solver.Interact, which explains the fix to #18910. * The inert_count field of InertCans wasn't actually used, so I removed it. Though I (Richard) did the implementation, Simon PJ was very involved in design and review. This updates the Haddock submodule to avoid #18932 by adding a type signature. ------------------------- Metric Decrease: T12227 T5030 T9872a T9872b T9872c Metric Increase: T9872d -------------------------
* [Sized Cmm] properly retain sizes.Moritz Angermann2020-11-262-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | This replaces all Word<N> = W<N># Word# and Int<N> = I<N># Int# with Word<N> = W<N># Word<N># and Int<N> = I<N># Int<N>#, thus providing us with properly sized primitives in the codegenerator instead of pretending they are all full machine words. This came up when implementing darwinpcs for arm64. The darwinpcs reqires us to pack function argugments in excess of registers on the stack. While most procedure call standards (pcs) assume arguments are just passed in 8 byte slots; and thus the caller does not know the exact signature to make the call, darwinpcs requires us to adhere to the prototype, and thus have the correct sizes. If we specify CInt in the FFI call, it should correspond to the C int, and not just be Word sized, when it's only half the size. This does change the expected output of T16402 but the new result is no less correct as it eliminates the narrowing (instead of the `and` as was previously done). Bumps the array, bytestring, text, and binary submodules. Co-Authored-By: Ben Gamari <ben@well-typed.com> Metric Increase: T13701 T14697
* Replace HsImplicitBndrs with HsOuterTyVarBndrsRyan Scott2020-11-0616-13/+82
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This refactors the GHC AST to remove `HsImplicitBndrs` and replace it with `HsOuterTyVarBndrs`, a type which records whether the outermost quantification in a type is explicit (i.e., with an outermost, invisible `forall`) or implicit. As a result of this refactoring, it is now evident in the AST where the `forall`-or-nothing rule applies: it's all the places that use `HsOuterTyVarBndrs`. See the revamped `Note [forall-or-nothing rule]` in `GHC.Hs.Type` (previously in `GHC.Rename.HsType`). Moreover, the places where `ScopedTypeVariables` brings lexically scoped type variables into scope are a subset of the places that adhere to the `forall`-or-nothing rule, so this also makes places that interact with `ScopedTypeVariables` easier to find. See the revamped `Note [Lexically scoped type variables]` in `GHC.Hs.Type` (previously in `GHC.Tc.Gen.Sig`). `HsOuterTyVarBndrs` are used in type signatures (see `HsOuterSigTyVarBndrs`) and type family equations (see `HsOuterFamEqnTyVarBndrs`). The main difference between the former and the latter is that the former cares about specificity but the latter does not. There are a number of knock-on consequences: * There is now a dedicated `HsSigType` type, which is the combination of `HsOuterSigTyVarBndrs` and `HsType`. `LHsSigType` is now an alias for an `XRec` of `HsSigType`. * Working out the details led us to a substantial refactoring of the handling of explicit (user-written) and implicit type-variable bindings in `GHC.Tc.Gen.HsType`. Instead of a confusing family of higher order functions, we now have a local data type, `SkolemInfo`, that controls how these binders are kind-checked. It remains very fiddly, not fully satisfying. But it's better than it was. Fixes #16762. Bumps the Haddock submodule. Co-authored-by: Simon Peyton Jones <simonpj@microsoft.com> Co-authored-by: Richard Eisenberg <rae@richarde.dev> Co-authored-by: Zubin Duggal <zubin@cmi.ac.in>
* Fix two constraint solving problemsSimon Peyton Jones2020-10-272-0/+19
| | | | | | | | | | | | | | | | | | | | | This patch fixes two problems in the constraint solver. * An actual bug #18555: we were floating out a constraint to eagerly, and that was ultimately fatal. It's explained in Note [Do not float blocked constraints] in GHC.Core.Constraint. This is all very delicate, but it's all going to become irrelevant when we stop floating constraints (#17656). * A major performance infelicity in the flattener. When flattening (ty |> co) we *never* generated Refl, even when there was nothing at all to do. Result: we would gratuitously rewrite the constraint to exactly the same thing, wasting work. Described in #18413, and came up again in #18855. Solution: exploit the special case by calling the new function castCoercionKind1. See Note [castCoercionKind1] in GHC.Core.Coercion
* Version bump: base-4.16 (#18712)Vladislav Zavialov2020-10-272-2/+2
| | | | Also bumps upper bounds on base in boot libraries (incl. submodules).
* Extend mAX_TUPLE_SIZE to 64GHC GitLab CI2020-10-152-11/+13
| | | | As well a ctuples and sums.
* Improve kind generalisation, error messagesSimon Peyton Jones2020-09-2419-52/+93
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch does two things: * It refactors GHC.Tc.Errors a bit. In debugging Quick Look I was forced to look in detail at error messages, and ended up doing a bit of refactoring, esp in mkTyVarEqErr'. It's still quite a mess, but a bit better, I think. * It makes a significant improvement to the kind checking of type and class declarations. Specifically, we now ensure that if kind checking fails with an unsolved constraint, all the skolems are in scope. That wasn't the case before, which led to some obscure error messages; and occasional failures with "no skolem info" (eg #16245). Both of these, and the main Quick Look patch itself, affect a /lot/ of error messages, as you can see from the number of files changed. I've checked them all; I think they are as good or better than before. Smaller things * I documented the various instances of VarBndr better. See Note [The VarBndr tyep and its uses] in GHC.Types.Var * Renamed GHC.Tc.Solver.simpl_top to simplifyTopWanteds * A bit of refactoring in bindExplicitTKTele, to avoid the footwork with Either. Simpler now. * Move promoteTyVar from GHC.Tc.Solver to GHC.Tc.Utils.TcMType Fixes #16245 (comment 211369), memorialised as typecheck/polykinds/T16245a Also fixes the three bugs in #18640
* Implement Quick Look impredicativitySimon Peyton Jones2020-09-241-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch implements Quick Look impredicativity (#18126), sticking very closely to the design in A quick look at impredicativity, Serrano et al, ICFP 2020 The main change is that a big chunk of GHC.Tc.Gen.Expr has been extracted to two new modules GHC.Tc.Gen.App GHC.Tc.Gen.Head which deal with typechecking n-ary applications, and the head of such applications, respectively. Both contain a good deal of documentation. Three other loosely-related changes are in this patch: * I implemented (partly by accident) points (2,3)) of the accepted GHC proposal "Clean up printing of foralls", namely https://github.com/ghc-proposals/ghc-proposals/blob/ master/proposals/0179-printing-foralls.rst (see #16320). In particular, see Note [TcRnExprMode] in GHC.Tc.Module - :type instantiates /inferred/, but not /specified/, quantifiers - :type +d instantiates /all/ quantifiers - :type +v is killed off That completes the implementation of the proposal, since point (1) was done in commit df08468113ab46832b7ac0a7311b608d1b418c4d Author: Krzysztof Gogolewski <krzysztof.gogolewski@tweag.io> Date: Mon Feb 3 21:17:11 2020 +0100 Always display inferred variables using braces * HsRecFld (which the renamer introduces for record field selectors), is now preserved by the typechecker, rather than being rewritten back to HsVar. This is more uniform, and turned out to be more convenient in the new scheme of things. * The GHCi debugger uses a non-standard unification that allows the unification variables to unify with polytypes. We used to hack this by using ImpredicativeTypes, but that doesn't work anymore so I introduces RuntimeUnkTv. See Note [RuntimeUnkTv] in GHC.Runtime.Heap.Inspect Updates haddock submodule. WARNING: this patch won't validate on its own. It was too hard to fully disentangle it from the following patch, on type errors and kind generalisation. Changes to tests * Fixes #9730 (test added) * Fixes #7026 (test added) * Fixes most of #8808, except function `g2'` which uses a section (which doesn't play with QL yet -- see #18126) Test added * Fixes #1330. NB Church1.hs subsumes Church2.hs, which is now deleted * Fixes #17332 (test added) * Fixes #4295 * This patch makes typecheck/should_run/T7861 fail. But that turns out to be a pre-existing bug: #18467. So I have just made T7861 into expect_broken(18467)
* Remove GADT self-reference check (#11554, #12081, #12174, fixes #15942)Artyom Kuznetsov2020-09-193-12/+12
| | | | Reverts 430f5c84dac1eab550110d543831a70516b5cac8
* Fix visible forall in ppr_ty (#18522)Vladislav Zavialov2020-08-063-0/+6
| | | | | | | Before this patch, this type: T :: forall k -> (k ~ k) => forall j -> k -> j -> Type was printed incorrectly as: T :: forall k j -> (k ~ k) => k -> j -> Type
* Care with occCheckExpand in kind of occurrencesSimon Peyton Jones2020-07-247-0/+58
| | | | | | | | | | | | | | | | | | | Issue #18451 showed that we could get an infinite type, through over-use of occCheckExpand in the kind of an /occurrence/ of a type variable. See Note [Occurrence checking: look inside kinds] in GHC.Core.Type This patch fixes the problem by making occCheckExpand less eager to expand synonyms in kinds. It also improves pretty printing of kinds, by *not* suppressing the kind on a tyvar-binder like (a :: Const Type b) where type Const p q = p. Even though the kind of 'a' is Type, we don't want to suppress the kind ascription. Example: the error message for polykinds/T18451{a,b}. See GHC.Core.TyCo.Ppr Note [Suppressing * kinds].
* Improve handling of data type return kindswip/T18300Simon Peyton Jones2020-07-033-0/+21
| | | | | | | | | | | | | | | | | | Following a long conversation with Richard, this patch tidies up the handling of return kinds for data/newtype declarations (vanilla, family, and instance). I have substantially edited the Notes in TyCl, so they would bear careful reading. Fixes #18300, #18357 In GHC.Tc.Instance.Family.newFamInst we were checking some Lint-like properties with ASSSERT. Instead Richard and I have added a proper linter for axioms, and called it from lintGblEnv, which in turn is called in tcRnModuleTcRnM New tests (T18300, T18357) cause an ASSERT failure in HEAD.
* Bump ghc-prim version to 0.7.0Ryan Scott2020-07-022-2/+2
| | | | Fixes #18279. Bumps the `text` submodule.
* Update testsuiteSylvain Henry2020-06-172-4/+2
| | | | | | | | | | | | | | * 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
* Linear types (#15981)Krzysztof Gogolewski2020-06-171-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This is the first step towards implementation of the linear types proposal (https://github.com/ghc-proposals/ghc-proposals/pull/111). It features * A language extension -XLinearTypes * Syntax for linear functions in the surface language * Linearity checking in Core Lint, enabled with -dlinear-core-lint * Core-to-core passes are mostly compatible with linearity * Fields in a data type can be linear or unrestricted; linear fields have multiplicity-polymorphic constructors. If -XLinearTypes is disabled, the GADT syntax defaults to linear fields The following items are not yet supported: * a # m -> b syntax (only prefix FUN is supported for now) * Full multiplicity inference (multiplicities are really only checked) * Decent linearity error messages * Linear let, where, and case expressions in the surface language (each of these currently introduce the unrestricted variant) * Multiplicity-parametric fields * Syntax for annotating lambda-bound or let-bound with a multiplicity * Syntax for non-linear/multiple-field-multiplicity records * Linear projections for records with a single linear field * Linear pattern synonyms * Multiplicity coercions (test LinearPolyType) A high-level description can be found at https://ghc.haskell.org/trac/ghc/wiki/LinearTypes/Implementation Following the link above you will find a description of the changes made to Core. This commit has been authored by * Richard Eisenberg * Krzysztof Gogolewski * Matthew Pickering * Arnaud Spiwack With contributions from: * Mark Barbone * Alexander Vershilov Updates haddock submodule.
* base: Bump to 4.15.0.0Ben Gamari2020-06-172-4/+4
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* Always use rnImplicitBndrs to bring implicit tyvars into scopeRyan Scott2020-06-104-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This implements a first step towards #16762 by changing the renamer to always use `rnImplicitBndrs` to bring implicitly bound type variables into scope. The main change is in `rnFamInstEqn` and `bindHsQTyVars`, which previously used _ad hoc_ methods of binding their implicit tyvars. There are a number of knock-on consequences: * One of the reasons that `rnFamInstEqn` used an _ad hoc_ binding mechanism was to give more precise source locations in `-Wunused-type-patterns` warnings. (See https://gitlab.haskell.org/ghc/ghc/issues/16762#note_273343 for an example of this.) However, these warnings are actually a little _too_ precise, since implicitly bound type variables don't have exact binding sites like explicitly bound type variables do. A similar problem existed for "`Different names for the same type variable`" errors involving implicit tyvars bound by `bindHsQTyVars`. Therefore, we simply accept the less precise (but more accurate) source locations from `rnImplicitBndrs` in `rnFamInstEqn` and `bindHsQTyVars`. See `Note [Source locations for implicitly bound type variables]` in `GHC.Rename.HsType` for the full story. * In order for `rnImplicitBndrs` to work in `rnFamInstEqn`, it needs to be able to look up names from the parent class (in the event that we are renaming an associated type family instance). As a result, `rnImplicitBndrs` now takes an argument of type `Maybe assoc`, which is `Just` in the event that a type family instance is associated with a class. * Previously, GHC kept track of three type synonyms for free type variables in the renamer: `FreeKiTyVars`, `FreeKiTyVarsDups` (which are allowed to contain duplicates), and `FreeKiTyVarsNoDups` (which contain no duplicates). However, making is a distinction between `-Dups` and `-NoDups` is now pointless, as all code that returns `FreeKiTyVars{,Dups,NoDups}` will eventually end up being passed to `rnImplicitBndrs`, which removes duplicates. As a result, I decided to just get rid of `FreeKiTyVarsDups` and `FreeKiTyVarsNoDups`, leaving only `FreeKiTyVars`. * The `bindLRdrNames` and `deleteBys` functions are now dead code, so I took the liberty of removing them.
* Simple subsumptionwip/T17775Simon Peyton Jones2020-06-0531-143/+121
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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)
* Explicit SpecificityGert-Jan Bottu2020-05-211-1/+1
| | | | | | | | | | | | | | | | | | | | Implementation for Ticket #16393. Explicit specificity allows users to manually create inferred type variables, by marking them with braces. This way, the user determines which variables can be instantiated through visible type application. The additional syntax is included in the parser, allowing users to write braces in type variable binders (type signatures, data constructors etc). This information is passed along through the renamer and verified in the type checker. The AST for type variable binders, data constructors, pattern synonyms, partial signatures and Template Haskell has been updated to include the specificity of type variables. Minor notes: - Bumps haddock submodule - Disables pattern match checking in GHC.Iface.Type with GHC 8.8
* Add regression tests for #16244, #16245, #16758Ryan Scott2020-05-055-0/+46
| | | | | | | | | | | | | | | | | | Commit e3c374cc5bd7eb49649b9f507f9f7740697e3f70 ended up fixing quite a few bugs: * This commit fixes #16244 completely. A regression test has been added. * This commit fixes one program from #16245. (The program in https://gitlab.haskell.org/ghc/ghc/issues/16245#note_211369 still panics, and the program in https://gitlab.haskell.org/ghc/ghc/issues/16245#note_211400 still loops infinitely.) A regression test has been added for this program. * This commit fixes #16758. Accordingly, this patch removes the `expect_broken` label from the `T16758` test case, moves it from `should_compile` to `should_fail` (as it should produce an error message), and checks in the expected stderr.
* GHC.Core.Opt renamingSylvain Henry2020-04-181-1/+1
| | | | | | | | | | | * GHC.Core.Op => GHC.Core.Opt * GHC.Core.Opt.Simplify.Driver => GHC.Core.Opt.Driver * GHC.Core.Opt.Tidy => GHC.Core.Tidy * GHC.Core.Opt.WorkWrap.Lib => GHC.Core.Opt.WorkWrap.Utils As discussed in: * https://mail.haskell.org/pipermail/ghc-devs/2020-April/018758.html * https://gitlab.haskell.org/ghc/ghc/issues/13009#note_264650
* Modules: type-checker (#13009)Sylvain Henry2020-04-072-2/+2
| | | | Update Haddock submodule
* Add regression test for #17963Ryan Scott2020-03-313-0/+29
| | | | | | | | The panic in #17963 happened to be fixed by commit e3c374cc5bd7eb49649b9f507f9f7740697e3f70. This patch adds a regression test to ensure that it remains fixed. Fixes #17963.
* Simplify treatment of heterogeneous equalityRichard Eisenberg2020-03-206-47/+45
| | | | | | | | | | | | | | | | | | | | | | | | | | 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.
* Modules: Core operations (#13009)Sylvain Henry2020-03-181-1/+1
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* Fix #17021 by checking more return kindsRichard Eisenberg2020-03-173-7/+7
| | | | | | | | | | All the details are in new Note [Datatype return kinds] in TcTyClsDecls. Test case: typecheck/should_fail/T17021{,b} typecheck/should_compile/T17021a Updates haddock submodule
* Wrap an implication around class-sig kind errorsSimon Peyton Jones2020-03-144-1/+22
| | | | | | | | | | | | | | | | | | | | | Ticket #17841 showed that we can get a kind error in a class signature, but lack an enclosing implication that binds its skolems. This patch * Adds the wrapping implication: the new call to checkTvConstraints in tcClassDecl1 * Simplifies the API to checkTvConstraints, which was not otherwise called at all. * Simplifies TcErrors.report_unsolved by *not* initialising the TidyEnv from the typechecker lexical envt. It's enough to do so from the free vars of the unsolved constraints; and we get silly renamings if we add variables twice: once from the lexical scope and once from the implication constraint.
* Re-implement unsafe coercions in terms of unsafe equality proofsSimon Peyton Jones2020-02-201-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | (Commit message written by Omer, most of the code is written by Simon and Richard) See Note [Implementing unsafeCoerce] for how unsafe equality proofs and the new unsafeCoerce# are implemented. New notes added: - [Checking for levity polymorphism] in CoreLint.hs - [Implementing unsafeCoerce] in base/Unsafe/Coerce.hs - [Patching magic definitions] in Desugar.hs - [Wiring in unsafeCoerce#] in Desugar.hs Only breaking change in this patch is unsafeCoerce# is not exported from GHC.Exts, instead of GHC.Prim. Fixes #17443 Fixes #16893 NoFib ----- -------------------------------------------------------------------------------- Program Size Allocs Instrs Reads Writes -------------------------------------------------------------------------------- CS -0.1% 0.0% -0.0% -0.0% -0.0% CSD -0.1% 0.0% -0.0% -0.0% -0.0% FS -0.1% 0.0% -0.0% -0.0% -0.0% S -0.1% 0.0% -0.0% -0.0% -0.0% VS -0.1% 0.0% -0.0% -0.0% -0.0% VSD -0.1% 0.0% -0.0% -0.0% -0.1% VSM -0.1% 0.0% -0.0% -0.0% -0.0% anna -0.0% 0.0% -0.0% -0.0% -0.0% ansi -0.1% 0.0% -0.0% -0.0% -0.0% atom -0.1% 0.0% -0.0% -0.0% -0.0% awards -0.1% 0.0% -0.0% -0.0% -0.0% banner -0.1% 0.0% -0.0% -0.0% -0.0% bernouilli -0.1% 0.0% -0.0% -0.0% -0.0% binary-trees -0.1% 0.0% -0.0% -0.0% -0.0% boyer -0.1% 0.0% -0.0% -0.0% -0.0% boyer2 -0.1% 0.0% -0.0% -0.0% -0.0% bspt -0.1% 0.0% -0.0% -0.0% -0.0% cacheprof -0.1% 0.0% -0.0% -0.0% -0.0% calendar -0.1% 0.0% -0.0% -0.0% -0.0% cichelli -0.1% 0.0% -0.0% -0.0% -0.0% circsim -0.1% 0.0% -0.0% -0.0% -0.0% clausify -0.1% 0.0% -0.0% -0.0% -0.0% comp_lab_zift -0.1% 0.0% -0.0% -0.0% -0.0% compress -0.1% 0.0% -0.0% -0.0% -0.0% compress2 -0.1% 0.0% -0.0% -0.0% -0.0% constraints -0.1% 0.0% -0.0% -0.0% -0.0% cryptarithm1 -0.1% 0.0% -0.0% -0.0% -0.0% cryptarithm2 -0.1% 0.0% -0.0% -0.0% -0.0% cse -0.1% 0.0% -0.0% -0.0% -0.0% digits-of-e1 -0.1% 0.0% -0.0% -0.0% -0.0% digits-of-e2 -0.1% 0.0% -0.0% -0.0% -0.0% dom-lt -0.1% 0.0% -0.0% -0.0% -0.0% eliza -0.1% 0.0% -0.0% -0.0% -0.0% event -0.1% 0.0% -0.0% -0.0% -0.0% exact-reals -0.1% 0.0% -0.0% -0.0% -0.0% exp3_8 -0.1% 0.0% -0.0% -0.0% -0.0% expert -0.1% 0.0% -0.0% -0.0% -0.0% fannkuch-redux -0.1% 0.0% -0.0% -0.0% -0.0% fasta -0.1% 0.0% -0.5% -0.3% -0.4% fem -0.1% 0.0% -0.0% -0.0% -0.0% fft -0.1% 0.0% -0.0% -0.0% -0.0% fft2 -0.1% 0.0% -0.0% -0.0% -0.0% fibheaps -0.1% 0.0% -0.0% -0.0% -0.0% fish -0.1% 0.0% -0.0% -0.0% -0.0% fluid -0.1% 0.0% -0.0% -0.0% -0.0% fulsom -0.1% 0.0% +0.0% +0.0% +0.0% gamteb -0.1% 0.0% -0.0% -0.0% -0.0% gcd -0.1% 0.0% -0.0% -0.0% -0.0% gen_regexps -0.1% 0.0% -0.0% -0.0% -0.0% genfft -0.1% 0.0% -0.0% -0.0% -0.0% gg -0.1% 0.0% -0.0% -0.0% -0.0% grep -0.1% 0.0% -0.0% -0.0% -0.0% hidden -0.1% 0.0% -0.0% -0.0% -0.0% hpg -0.1% 0.0% -0.0% -0.0% -0.0% ida -0.1% 0.0% -0.0% -0.0% -0.0% infer -0.1% 0.0% -0.0% -0.0% -0.0% integer -0.1% 0.0% -0.0% -0.0% -0.0% integrate -0.1% 0.0% -0.0% -0.0% -0.0% k-nucleotide -0.1% 0.0% -0.0% -0.0% -0.0% kahan -0.1% 0.0% -0.0% -0.0% -0.0% knights -0.1% 0.0% -0.0% -0.0% -0.0% lambda -0.1% 0.0% -0.0% -0.0% -0.0% last-piece -0.1% 0.0% -0.0% -0.0% -0.0% lcss -0.1% 0.0% -0.0% -0.0% -0.0% life -0.1% 0.0% -0.0% -0.0% -0.0% lift -0.1% 0.0% -0.0% -0.0% -0.0% linear -0.1% 0.0% -0.0% -0.0% -0.0% listcompr -0.1% 0.0% -0.0% -0.0% -0.0% listcopy -0.1% 0.0% -0.0% -0.0% -0.0% maillist -0.1% 0.0% -0.0% -0.0% -0.0% mandel -0.1% 0.0% -0.0% -0.0% -0.0% mandel2 -0.1% 0.0% -0.0% -0.0% -0.0% mate -0.1% 0.0% -0.0% -0.0% -0.0% minimax -0.1% 0.0% -0.0% -0.0% -0.0% mkhprog -0.1% 0.0% -0.0% -0.0% -0.0% multiplier -0.1% 0.0% -0.0% -0.0% -0.0% n-body -0.1% 0.0% -0.0% -0.0% -0.0% nucleic2 -0.1% 0.0% -0.0% -0.0% -0.0% para -0.1% 0.0% -0.0% -0.0% -0.0% paraffins -0.1% 0.0% -0.0% -0.0% -0.0% parser -0.1% 0.0% -0.0% -0.0% -0.0% parstof -0.1% 0.0% -0.0% -0.0% -0.0% pic -0.1% 0.0% -0.0% -0.0% -0.0% pidigits -0.1% 0.0% -0.0% -0.0% -0.0% power -0.1% 0.0% -0.0% -0.0% -0.0% pretty -0.1% 0.0% -0.1% -0.1% -0.1% primes -0.1% 0.0% -0.0% -0.0% -0.0% primetest -0.1% 0.0% -0.0% -0.0% -0.0% prolog -0.1% 0.0% -0.0% -0.0% -0.0% puzzle -0.1% 0.0% -0.0% -0.0% -0.0% queens -0.1% 0.0% -0.0% -0.0% -0.0% reptile -0.1% 0.0% -0.0% -0.0% -0.0% reverse-complem -0.1% 0.0% -0.0% -0.0% -0.0% rewrite -0.1% 0.0% -0.0% -0.0% -0.0% rfib -0.1% 0.0% -0.0% -0.0% -0.0% rsa -0.1% 0.0% -0.0% -0.0% -0.0% scc -0.1% 0.0% -0.1% -0.1% -0.1% sched -0.1% 0.0% -0.0% -0.0% -0.0% scs -0.1% 0.0% -0.0% -0.0% -0.0% simple -0.1% 0.0% -0.0% -0.0% -0.0% solid -0.1% 0.0% -0.0% -0.0% -0.0% sorting -0.1% 0.0% -0.0% -0.0% -0.0% spectral-norm -0.1% 0.0% -0.0% -0.0% -0.0% sphere -0.1% 0.0% -0.0% -0.0% -0.0% symalg -0.1% 0.0% -0.0% -0.0% -0.0% tak -0.1% 0.0% -0.0% -0.0% -0.0% transform -0.1% 0.0% -0.0% -0.0% -0.0% treejoin -0.1% 0.0% -0.0% -0.0% -0.0% typecheck -0.1% 0.0% -0.0% -0.0% -0.0% veritas -0.0% 0.0% -0.0% -0.0% -0.0% wang -0.1% 0.0% -0.0% -0.0% -0.0% wave4main -0.1% 0.0% -0.0% -0.0% -0.0% wheel-sieve1 -0.1% 0.0% -0.0% -0.0% -0.0% wheel-sieve2 -0.1% 0.0% -0.0% -0.0% -0.0% x2n1 -0.1% 0.0% -0.0% -0.0% -0.0% -------------------------------------------------------------------------------- Min -0.1% 0.0% -0.5% -0.3% -0.4% Max -0.0% 0.0% +0.0% +0.0% +0.0% Geometric Mean -0.1% -0.0% -0.0% -0.0% -0.0% Test changes ------------ - break006 is marked as broken, see #17833 - The compiler allocates less when building T14683 (an unsafeCoerce#- heavy happy-generated code) on 64-platforms. Allocates more on 32-bit platforms. - Rest of the increases are tiny amounts (still enough to pass the threshold) in micro-benchmarks. I briefly looked at each one in a profiling build: most of the increased allocations seem to be because of random changes in the generated code. Metric Decrease: T14683 Metric Increase: T12150 T12234 T12425 T13035 T14683 T5837 T6048 Co-Authored-By: Richard Eisenberg <rae@cs.brynmawr.edu> Co-Authored-By: Ömer Sinan Ağacan <omeragacan@gmail.com>
* Always display inferred variables using bracesKrzysztof Gogolewski2020-02-129-12/+16
| | | | | | | | | | | | | 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)
* Fix scoping of TyCon binders in TcTyClsDeclsSimon Peyton Jones2020-02-012-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch fixes #17566 by refactoring the way we decide the final identity of the tyvars in the TyCons of a possibly-recursive nest of type and class decls, possibly with associated types. It's all laid out in Note [Swizzling the tyvars before generaliseTcTyCon] Main changes: * We have to generalise each decl (with its associated types) all at once: TcTyClsDecls.generaliseTyClDecl * The main new work is done in TcTyClsDecls.swizzleTcTyConBndrs * The mysterious TcHsSyn.zonkRecTyVarBndrs dies altogether Other smaller things: * A little refactoring, moving bindTyClTyVars from tcTyClDecl1 to tcDataDefn, tcSynRhs, etc. Clearer, reduces the number of parameters * Reduce the amount of swizzling required. Specifically, bindExplicitTKBndrs_Q_Tv doesn't need to clone a new Name for the TyVarTv, and not cloning means that in the vasly common case, swizzleTyConBndrs is a no-op In detail: Rename newTyVarTyVar --> cloneTyVarTyVar Add newTyVarTyTyVar that doesn't clone Use the non-cloning newTyVarTyVar in bindExplicitTKBndrs_Q_Tv Rename newFlexiKindedTyVarTyVar --> cloneFlexiKindedTyVarTyVar * Define new utility function and use it HsDecls.familyDeclName :: FamilyDecl (GhcPass p) -> IdP (GhcPass p) Updates haddock submodule.
* Don't zap to Any; error insteadRichard Eisenberg2020-01-123-2/+20
| | | | | | | | | 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.
* Warn on inferred polymorphic recursionRichard Eisenberg2019-12-115-1/+7
| | | | | | | | | | | Silly users sometimes try to use visible dependent quantification and polymorphic recursion without a CUSK or SAK. This causes unexpected errors. So we now adjust expectations with a bit of helpful messaging. Closes #17541 and closes #17131. test cases: dependent/should_fail/T{17541{,b},17131}
* Pretty-printing of the * kindVladislav Zavialov2019-12-055-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 (*) -> *
* Strip parentheses in expressions contexts in error messagesVladislav Zavialov2019-11-191-1/+1
| | | | This makes error messages a tad less noisy.
* base: Bump version to 4.14.0.0Ben Gamari2019-11-142-2/+2
| | | | | Metric Increase: T4801
* Standalone kind signatures (#16794)wip/top-level-kind-signaturesVladislav Zavialov2019-09-252-0/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implements GHC Proposal #54: .../ghc-proposals/blob/master/proposals/0054-kind-signatures.rst With this patch, a type constructor can now be given an explicit standalone kind signature: {-# LANGUAGE StandaloneKindSignatures #-} type Functor :: (Type -> Type) -> Constraint class Functor f where fmap :: (a -> b) -> f a -> f b This is a replacement for CUSKs (complete user-specified kind signatures), which are now scheduled for deprecation. User-facing changes ------------------- * A new extension flag has been added, -XStandaloneKindSignatures, which implies -XNoCUSKs. * There is a new syntactic construct, a standalone kind signature: type <name> :: <kind> Declarations of data types, classes, data families, type families, and type synonyms may be accompanied by a standalone kind signature. * A standalone kind signature enables polymorphic recursion in types, just like a function type signature enables polymorphic recursion in terms. This obviates the need for CUSKs. * TemplateHaskell AST has been extended with 'KiSigD' to represent standalone kind signatures. * GHCi :info command now prints the kind signature of type constructors: ghci> :info Functor type Functor :: (Type -> Type) -> Constraint ... Limitations ----------- * 'forall'-bound type variables of a standalone kind signature do not scope over the declaration body, even if the -XScopedTypeVariables is enabled. See #16635 and #16734. * Wildcards are not allowed in standalone kind signatures, as partial signatures do not allow for polymorphic recursion. * Associated types may not be given an explicit standalone kind signature. Instead, they are assumed to have a CUSK if the parent class has a standalone kind signature and regardless of the -XCUSKs flag. * Standalone kind signatures do not support multiple names at the moment: type T1, T2 :: Type -> Type -- rejected type T1 = Maybe type T2 = Either String See #16754. * Creative use of equality constraints in standalone kind signatures may lead to GHC panics: type C :: forall (a :: Type) -> a ~ Int => Constraint class C a where f :: C a => a -> Int See #16758. Implementation notes -------------------- * The heart of this patch is the 'kcDeclHeader' function, which is used to kind-check a declaration header against its standalone kind signature. It does so in two rounds: 1. check user-written binders 2. instantiate invisible binders a la 'checkExpectedKind' * 'kcTyClGroup' now partitions declarations into declarations with a standalone kind signature or a CUSK (kinded_decls) and declarations without either (kindless_decls): * 'kinded_decls' are kind-checked with 'checkInitialKinds' * 'kindless_decls' are kind-checked with 'getInitialKinds' * DerivInfo has been extended with a new field: di_scoped_tvs :: ![(Name,TyVar)] These variables must be added to the context in case the deriving clause references tcTyConScopedTyVars. See #16731.
* testsuite: Set -dinitial-unique when reversing uniquesBen Gamari2019-07-181-1/+1
| | | | | Otherwise the unique counter starts at 0, causing us to immediately underflow.
* Fix over-eager implication constraint discardSimon Peyton Jones2019-07-045-0/+50
| | | | | | | | Ticket #16247 showed that we were discarding an implication constraint that had empty ic_wanted, when we still needed to keep it so we could check whether it had a bad telescope. Happily it's a one line fix. All the rest is comments!
* Add a missing zonk (fixes #16902)Simon Peyton Jones2019-07-043-0/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | In the eager unifier, when unifying (tv1 ~ tv2), when we decide to swap them over, to unify (tv2 ~ tv1), I'd forgotten to ensure that tv1's kind was fully zonked, which is an invariant of uUnfilledTyVar2. That could lead us to build an infinite kind, or (in the case of #16902) update the same unification variable twice. Yikes. Now we get an error message rather than non-termination, which is much better. The error message is not great, but it's a very strange program, and I can't see an easy way to improve it, so for now I'm just committing this fix. Here's the decl data F (a :: k) :: (a ~~ k) => Type where MkF :: F a and the rather error message of which I am not proud T16902.hs:11:10: error: • Expected a type, but found something with kind ‘a1’ • In the type ‘F a’
* Implement the -XUnliftedNewtypes extension.Andrew Martin2019-06-141-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | GHC Proposal: 0013-unlifted-newtypes.rst Discussion: https://github.com/ghc-proposals/ghc-proposals/pull/98 Issues: #15219, #1311, #13595, #15883 Implementation Details: Note [Implementation of UnliftedNewtypes] Note [Unifying data family kinds] Note [Compulsory newtype unfolding] This patch introduces the -XUnliftedNewtypes extension. When this extension is enabled, GHC drops the restriction that the field in a newtype must be of kind (TYPE 'LiftedRep). This allows types like Int# and ByteArray# to be used in a newtype. Additionally, coerce is made levity-polymorphic so that it can be used with newtypes over unlifted types. The bulk of the changes are in TcTyClsDecls.hs. With -XUnliftedNewtypes, getInitialKind is more liberal, introducing a unification variable to return the kind (TYPE r0) rather than just returning (TYPE 'LiftedRep). When kind-checking a data constructor with kcConDecl, we attempt to unify the kind of a newtype with the kind of its field's type. When typechecking a data declaration with tcTyClDecl, we again perform a unification. See the implementation note for more on this. Co-authored-by: Richard Eisenberg <rae@richarde.dev>
* Preserve ShadowInfo when rewriting evidenceSimon Peyton Jones2019-06-071-4/+4
| | | | | | | | | | | | | | | When the canonicaliser rewrites evidence of a Wanted, it should preserve the ShadowInfo (ctev_nosh) field. That is, a WDerive should rewrite to WDerive, and WOnly to WOnly. Previously we were unconditionally making a WDeriv, thereby rewriting WOnly to WDeriv. This bit Nick Frisby (issue #16735) in the context of his plugin, but we don't have a compact test case. The fix is simple, but does involve a bit more plumbing, to pass the old ShadowInfo around, to use when building the new Wanted.
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