1. 01 Mar, 2019 1 commit
    • Ryan Scott's avatar
      Visible dependent quantification · c26d299d
      Ryan Scott authored
      This implements GHC proposal 35
      (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0035-forall-arrow.rst)
      by adding the ability to write kinds with
      visible dependent quantification (VDQ).
      
      Most of the work for supporting VDQ was actually done _before_ this
      patch. That is, GHC has been able to reason about kinds with VDQ for
      some time, but it lacked the ability to let programmers directly
      write these kinds in the source syntax. This patch is primarly about
      exposing this ability, by:
      
      * Changing `HsForAllTy` to add an additional field of type
        `ForallVisFlag` to distinguish between invisible `forall`s (i.e,
        with dots) and visible `forall`s (i.e., with arrows)
      * Changing `Parser.y` accordingly
      
      The rest of the patch mostly concerns adding validity checking to
      ensure that VDQ is never used in the type of a term (as permitting
      this would require full-spectrum dependent types). This is
      accomplished by:
      
      * Adding a `vdqAllowed` predicate to `TcValidity`.
      * Introducing `splitLHsSigmaTyInvis`, a variant of `splitLHsSigmaTy`
        that only splits invisible `forall`s. This function is used in
        certain places (e.g., in instance declarations) to ensure that GHC
        doesn't try to split visible `forall`s (e.g., if it tried splitting
        `instance forall a -> Show (Blah a)`, then GHC would mistakenly
        allow that declaration!)
      
      This also updates Template Haskell by introducing a new `ForallVisT`
      constructor to `Type`.
      
      Fixes #16326. Also fixes #15658 by documenting this feature in the
      users' guide.
      c26d299d
  2. 03 Jan, 2019 1 commit
    • My Nguyen's avatar
      Visible kind application · 17bd1635
      My Nguyen authored
      Summary:
      This patch implements visible kind application (GHC Proposal 15/#12045), as well as #15360 and #15362.
      It also refactors unnamed wildcard handling, and requires that type equations in type families in Template Haskell be
      written with full type on lhs. PartialTypeSignatures are on and warnings are off automatically with visible kind
      application, just like in term-level.
      
      There are a few remaining issues with this patch, as documented in
      ticket #16082.
      
      Includes a submodule update for Haddock.
      
      Test Plan: Tests T12045a/b/c/TH1/TH2, T15362, T15592a
      
      Reviewers: simonpj, goldfire, bgamari, alanz, RyanGlScott, Iceland_jack
      
      Subscribers: ningning, Iceland_jack, RyanGlScott, int-index, rwbarton, mpickering, carter
      
      GHC Trac Issues: `#12045`, `#15362`, `#15592`, `#15788`, `#15793`, `#15795`, `#15797`, `#15799`, `#15801`, `#15807`, `#15816`
      
      Differential Revision: https://phabricator.haskell.org/D5229
      17bd1635
  3. 14 Sep, 2018 1 commit
    • Michael Sloan's avatar
      Add support for ImplicitParams and RecursiveDo in TH · 9c6b7493
      Michael Sloan authored
      Summary:
      This adds TH support for the ImplicitParams and RecursiveDo extensions.
      
      I'm submitting this as one review because I cannot cleanly make
      the two commits independent.
      
      Initially, my goal was just to add ImplicitParams support, and
      I found that reasonably straightforward, so figured I might
      as well use my newfound knowledge to address some other TH omissions.
      
      Test Plan: Validate
      
      Reviewers: goldfire, austin, bgamari, RyanGlScott
      
      Reviewed By: RyanGlScott
      
      Subscribers: carter, RyanGlScott, thomie
      
      GHC Trac Issues: #1262
      
      Differential Revision: https://phabricator.haskell.org/D1979
      9c6b7493
  4. 05 Jun, 2018 1 commit
    • Ryan Scott's avatar
      Introduce DerivingVia · 8ed8b037
      Ryan Scott authored
      This implements the `DerivingVia` proposal put forth in
      https://github.com/ghc-proposals/ghc-proposals/pull/120.
      
      This introduces the `DerivingVia` deriving strategy. This is a
      generalization of `GeneralizedNewtypeDeriving` that permits the user
      to specify the type to `coerce` from.
      
      The major change in this patch is the introduction of the
      `ViaStrategy` constructor to `DerivStrategy`, which takes a type
      as a field. As a result, `DerivStrategy` is no longer a simple
      enumeration type, but rather something that must be renamed and
      typechecked. The process by which this is done is explained more
      thoroughly in section 3 of this paper
      ( https://www.kosmikus.org/DerivingVia/deriving-via-paper.pdf ),
      although I have inlined the relevant parts into Notes where possible.
      
      There are some knock-on changes as well. I took the opportunity to
      do some refactoring of code in `TcDeriv`, especially the
      `mkNewTypeEqn` function, since it was bundling all of the logic for
      (1) deriving instances for newtypes and
      (2) `GeneralizedNewtypeDeriving`
      into one huge broth. `DerivingVia` reuses much of part (2), so that
      was factored out as much as possible.
      
      Bumps the Haddock submodule.
      
      Test Plan: ./validate
      
      Reviewers: simonpj, bgamari, goldfire, alanz
      
      Subscribers: alanz, goldfire, rwbarton, thomie, mpickering, carter
      
      GHC Trac Issues: #15178
      
      Differential Revision: https://phabricator.haskell.org/D4684
      8ed8b037
  5. 04 Dec, 2017 1 commit
  6. 19 Sep, 2017 1 commit
    • Herbert Valerio Riedel's avatar
      compiler: introduce custom "GhcPrelude" Prelude · f63bc730
      Herbert Valerio Riedel authored
      This switches the compiler/ component to get compiled with
      -XNoImplicitPrelude and a `import GhcPrelude` is inserted in all
      modules.
      
      This is motivated by the upcoming "Prelude" re-export of
      `Semigroup((<>))` which would cause lots of name clashes in every
      modulewhich imports also `Outputable`
      
      Reviewers: austin, goldfire, bgamari, alanz, simonmar
      
      Reviewed By: bgamari
      
      Subscribers: goldfire, rwbarton, thomie, mpickering, bgamari
      
      Differential Revision: https://phabricator.haskell.org/D3989
      f63bc730
  7. 28 Jul, 2017 1 commit
    • Ryan Scott's avatar
      Merge types and kinds in DsMeta · b3b564fb
      Ryan Scott authored
      Summary:
      Types and kinds are now the same in GHC... well, except in the code
      that involves Template Haskell, where types and kinds are given separate
      treatment. This aims to unify that treatment in the `DsMeta` module.
      
      The gist of this patch is replacing all uses of `repLKind` with `repLTy`.
      This is isn't quite as simple as one might imagine, since `repLTy` returns a
      `Core (Q Type)` (a monadic expression), whereas `repLKind` returns a
      `Core Kind` (a pure expression). This causes many awkward impedance mismatches.
      
      One option would be to change every combinator in `Language.Haskell.TH.Lib` to
      take `KindQ` as an argument instead of `Kind`. But this would be a breaking
      change of colossal proportions.
      
      Instead, this patch takes a somewhat different approach. This migrates the
      existing `Language.Haskell.TH.Lib` module to
      `Language.Haskell.TH.Lib.Internal`, and changes all `Kind`-related combinators
      in `Language.Haskell.TH.Lib.Internal` to live in `Q`. The new
      `Language.Haskell.TH.Lib` module then re-exports most of
      `Language.Haskell.TH.Lib.Internal` with the exception of the `Kind`-related
      combinators, for which it redefines them to be their current definitions (which
      don't live in `Q`). This allows us to retain backwards compatibility with
      previous `template-haskell` releases, but more importantly, it allows GHC to
      make as many changes to the `Internal` code as it wants for its purposes
      without fear of disrupting the public API.
      
      This solves half of #11785 (the other half being `TcSplice`).
      
      Test Plan: ./validate
      
      Reviewers: goldfire, austin, bgamari
      
      Reviewed By: goldfire
      
      Subscribers: rwbarton, thomie
      
      GHC Trac Issues: #11785
      
      Differential Revision: https://phabricator.haskell.org/D3751
      b3b564fb
  8. 11 Jul, 2017 1 commit
  9. 12 Jun, 2017 1 commit
  10. 18 Feb, 2017 1 commit
    • Ben Gamari's avatar
      Type-indexed Typeable · 8fa4bf9a
      Ben Gamari authored
      This at long last realizes the ideas for type-indexed Typeable discussed in A
      Reflection on Types (#11011). The general sketch of the project is described on
      the Wiki (Typeable/BenGamari). The general idea is that we are adding a type
      index to `TypeRep`,
      
          data TypeRep (a :: k)
      
      This index allows the typechecker to reason about the type represented by the `TypeRep`.
      This index representation mechanism is exposed as `Type.Reflection`, which also provides
      a number of patterns for inspecting `TypeRep`s,
      
      ```lang=haskell
      pattern TRFun :: forall k (fun :: k). ()
                    => forall (r1 :: RuntimeRep) (r2 :: RuntimeRep)
                              (arg :: TYPE r1) (res :: TYPE r2).
                       (k ~ Type, fun ~~ (arg -> res))
                    => TypeRep arg
                    -> TypeRep res
                    -> TypeRep fun
      
      pattern TRApp :: forall k2 (t :: k2). ()
                    => forall k1 (a :: k1 -> k2) (b :: k1). (t ~ a b)
                    => TypeRep a -> TypeRep b -> TypeRep t
      
      -- | Pattern match on a type constructor.
      pattern TRCon :: forall k (a :: k). TyCon -> TypeRep a
      
      -- | Pattern match on a type constructor including its instantiated kind
      -- variables.
      pattern TRCon' :: forall k (a :: k). TyCon -> [SomeTypeRep] -> TypeRep a
      ```
      
      In addition, we give the user access to the kind of a `TypeRep` (#10343),
      
          typeRepKind :: TypeRep (a :: k) -> TypeRep k
      
      Moreover, all of this plays nicely with 8.2's levity polymorphism, including the
      newly levity polymorphic (->) type constructor.
      
      Library changes
      ---------------
      
      The primary change here is the introduction of a Type.Reflection module to base.
      This module provides access to the new type-indexed TypeRep introduced in this
      patch. We also continue to provide the unindexed Data.Typeable interface, which
      is simply a type synonym for the existentially quantified SomeTypeRep,
      
          data SomeTypeRep where SomeTypeRep :: TypeRep a -> SomeTypeRep
      
      Naturally, this change also touched Data.Dynamic, which can now export the
      Dynamic data constructor. Moreover, I removed a blanket reexport of
      Data.Typeable from Data.Dynamic (which itself doesn't even import Data.Typeable
      now).
      
      We also add a kind heterogeneous type equality type, (:~~:), to
      Data.Type.Equality.
      
      Implementation
      --------------
      
      The implementation strategy is described in Note [Grand plan for Typeable] in
      TcTypeable. None of it was difficult, but it did exercise a number of parts of
      the new levity polymorphism story which had not yet been exercised, which took
      some sorting out.
      
      The rough idea is that we augment the TyCon produced for each type constructor
      with information about the constructor's kind (which we call a KindRep). This
      allows us to reconstruct the monomorphic result kind of an particular
      instantiation of a type constructor given its kind arguments.
      
      Unfortunately all of this takes a fair amount of work to generate and send
      through the compilation pipeline. In particular, the KindReps can unfortunately
      get quite large. Moreover, the simplifier will float out various pieces of them,
      resulting in numerous top-level bindings. Consequently we mark the KindRep
      bindings as noinline, ensuring that the float-outs don't make it into the
      interface file. This is important since there is generally little benefit to
      inlining KindReps and they would otherwise strongly affect compiler performance.
      
      Performance
      -----------
      
      Initially I was hoping to also clear up the remaining holes in Typeable's
      coverage by adding support for both unboxed tuples (#12409) and unboxed sums
      (#13276). While the former was fairly straightforward, the latter ended up being
      quite difficult: while the implementation can support them easily, enabling this
      support causes thousands of Typeable bindings to be emitted to the GHC.Types as
      each arity-N sum tycon brings with it N promoted datacons, each of which has a
      KindRep whose size which itself scales with N. Doing this was simply too
      expensive to be practical; consequently I've disabled support for the time
      being.
      
      Even after disabling sums this change regresses compiler performance far more
      than I would like. In particular there are several testcases in the testsuite
      which consist mostly of types which regress by over 30% in compiler allocations.
      These include (considering the "bytes allocated" metric),
      
       * T1969:  +10%
       * T10858: +23%
       * T3294:  +19%
       * T5631:  +41%
       * T6048:  +23%
       * T9675:  +20%
       * T9872a: +5.2%
       * T9872d: +12%
       * T9233:  +10%
       * T10370: +34%
       * T12425: +30%
       * T12234: +16%
       * 13035:  +17%
       * T4029:  +6.1%
      
      I've spent quite some time chasing down the source of this regression and while
      I was able to make som improvements, I think this approach of generating
      Typeable bindings at time of type definition is doomed to give us unnecessarily
      large compile-time overhead.
      
      In the future I think we should consider moving some of all of the Typeable
      binding generation logic back to the solver (where it was prior to
      91c6b1f5). I've opened #13261 documenting this
      proposal.
      8fa4bf9a
  11. 26 Jan, 2017 2 commits
  12. 09 Dec, 2016 1 commit
    • Ryan Scott's avatar
      Rename TH constructors for deriving strategies · 5349d648
      Ryan Scott authored
      After talking to Richard, he and I concluded that choosing the rather
      common name `Newtype` to represent the corresponding deriving strategy
      in Template Haskell was a poor choice of name. I've opted to rename it
      to something less common (`NewtypeStrategy`) while we still have time. I
      also renamed the corrsponding datatype in the GHC internals so as to
      match it.
      
      Reviewers: austin, goldfire, hvr, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: thomie, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D2814
      
      GHC Trac Issues: #10598
      5349d648
  13. 01 Oct, 2016 1 commit
    • Ryan Scott's avatar
      Implement deriving strategies · 9e862765
      Ryan Scott authored
      Allows users to explicitly request which approach to `deriving` to use
      via keywords, e.g.,
      
      ```
      newtype Foo = Foo Bar
        deriving Eq
        deriving stock    Ord
        deriving newtype Show
      ```
      
      Fixes #10598. Updates haddock submodule.
      
      Test Plan: ./validate
      
      Reviewers: hvr, kosmikus, goldfire, alanz, bgamari, simonpj, austin,
      erikd, simonmar
      
      Reviewed By: alanz, bgamari, simonpj
      
      Subscribers: thomie, mpickering, oerjan
      
      Differential Revision: https://phabricator.haskell.org/D2280
      
      GHC Trac Issues: #10598
      9e862765
  14. 29 Aug, 2016 1 commit
  15. 23 Aug, 2016 1 commit
    • Ryan Scott's avatar
      Template Haskell support for unboxed sums · 613d7455
      Ryan Scott authored
      This adds new constructors `UnboxedSumE`, `UnboxedSumT`, and
      `UnboxedSumP` to represent unboxed sums in Template Haskell.
      
      One thing you can't currently do is, e.g., `reify ''(#||#)`, since I
      don't believe unboxed sum type/data constructors can be written in
      prefix form.  I will look at fixing that as part of #12514.
      
      Fixes #12478.
      
      Test Plan: make test TEST=T12478_{1,2,3}
      
      Reviewers: osa1, goldfire, austin, bgamari
      
      Reviewed By: goldfire, bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2448
      
      GHC Trac Issues: #12478
      613d7455
  16. 12 May, 2016 1 commit
  17. 17 Apr, 2016 1 commit
  18. 22 Dec, 2015 2 commits
    • Simon Peyton Jones's avatar
      Refactor named wildcards (again) · 575a98e4
      Simon Peyton Jones authored
      Michal's work on #10982, #11098, refactored the handling of named
      wildcards by making them more like ordinary type variables.
      
      This patch takes the same idea to its logical conclusion, resulting
      in a much tidier, tighter implementation.
      
      Read Note [The wildcard story for types] in HsTypes.
      
      Changes:
      
       * Named wildcards are ordinary type variables, throughout
      
       * HsType no longer has a data constructor for named wildcards
         (was NamedWildCard in HsWildCardInfo).  Named wildcards are
         simply HsTyVars
      
       * Similarly named wildcards disappear from Template Haskell
      
       * I refactored RnTypes to avoid polluting LocalRdrEnv with something
         as narrow as named wildcards.  Instead the named wildcard set is
         carried in RnTyKiEnv.
      
      There is a submodule update for Haddock.
      575a98e4
    • Ryan Scott's avatar
      Rework Template Haskell's handling of strictness · f975b0b1
      Ryan Scott authored
      Currently, Template Haskell's treatment of strictness is not enough to
      cover all possible combinations of unpackedness and strictness. In
      addition, it isn't equipped to deal with new features (such as
      `-XStrictData`) which can change a datatype's fields' strictness during
      compilation.
      
      To address this, I replaced TH's `Strict` datatype with
      `SourceUnpackedness` and `SourceStrictness` (which give the programmer a
      more complete toolkit to configure a datatype field's strictness than
      just `IsStrict`, `IsLazy`, and `Unpack`). I also added the ability to
      reify a constructor fields' strictness post-compilation through the
      `reifyConStrictness` function.
      
      Fixes #10697.
      
      Test Plan: ./validate
      
      Reviewers: simonpj, goldfire, bgamari, austin
      
      Reviewed By: goldfire, bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1603
      
      GHC Trac Issues: #10697
      f975b0b1
  19. 21 Dec, 2015 1 commit
  20. 30 Oct, 2015 1 commit
    • Ben Gamari's avatar
      Generate Typeable info at definition sites · 91c6b1f5
      Ben Gamari authored
      This is the second attempt at merging D757.
      
      This patch implements the idea floated in Trac #9858, namely that we
      should generate type-representation information at the data type
      declaration site, rather than when solving a Typeable constraint.
      
      However, this turned out quite a bit harder than I expected. I still
      think it's the right thing to do, and it's done now, but it was quite
      a struggle.
      
      See particularly
      
       * Note [Grand plan for Typeable] in TcTypeable (which is a new module)
       * Note [The overall promotion story] in DataCon (clarifies existing
      stuff)
      
      The most painful bit was that to generate Typeable instances (ie
      TyConRepName bindings) for every TyCon is tricky for types in ghc-prim
      etc:
      
       * We need to have enough data types around to *define* a TyCon
       * Many of these types are wired-in
      
      Also, to minimise the code generated for each data type, I wanted to
      generate pure data, not CAFs with unpackCString# stuff floating about.
      
      Performance
      ~~~~~~~~~~~
      Three perf/compiler tests start to allocate quite a bit more. This isn't
      surprising, because they all allocate zillions of data types, with
      practically no other code, esp. T1969
      
       * T1969:    GHC allocates 19% more
       * T4801:    GHC allocates 13% more
       * T5321FD:  GHC allocates 13% more
       * T9675:    GHC allocates 11% more
       * T783:     GHC allocates 11% more
       * T5642:    GHC allocates 10% more
      
      I'm treating this as acceptable. The payoff comes in Typeable-heavy
      code.
      
      Remaining to do
      ~~~~~~~~~~~~~~~
      
       * I think that "TyCon" and "Module" are over-generic names to use for
         the runtime type representations used in GHC.Typeable. Better might
      be
         "TrTyCon" and "TrModule". But I have not yet done this
      
       * Add more info the the "TyCon" e.g. source location where it was
         defined
      
       * Use the new "Module" type to help with Trac Trac #10068
      
       * It would be possible to generate TyConRepName (ie Typeable
         instances) selectively rather than all the time. We'd need to persist
         the information in interface files. Lacking a motivating reason I
      have
         not done this, but it would not be difficult.
      
      Refactoring
      ~~~~~~~~~~~
      As is so often the case, I ended up refactoring more than I intended.
      In particular
      
       * In TyCon, a type *family* (whether type or data) is repesented by a
         FamilyTyCon
           * a algebraic data type (including data/newtype instances) is
             represented by AlgTyCon This wasn't true before; a data family
             was represented as an AlgTyCon. There are some corresponding
             changes in IfaceSyn.
      
           * Also get rid of the (unhelpfully named) tyConParent.
      
       * In TyCon define 'Promoted', isomorphic to Maybe, used when things are
         optionally promoted; and use it elsewhere in GHC.
      
       * Cleanup handling of knownKeyNames
      
       * Each TyCon, including promoted TyCons, contains its TyConRepName, if
         it has one. This is, in effect, the name of its Typeable instance.
      
      Updates haddock submodule
      
      Test Plan: Let Harbormaster validate
      
      Reviewers: austin, hvr, goldfire
      
      Subscribers: goldfire, thomie
      
      Differential Revision: https://phabricator.haskell.org/D1404
      
      GHC Trac Issues: #9858
      91c6b1f5
  21. 29 Oct, 2015 2 commits
    • Ben Gamari's avatar
      Revert "Generate Typeable info at definition sites" · bbaf76f9
      Ben Gamari authored
      This reverts commit bef2f03e.
      
      This merge was botched
      
      Also reverts haddock submodule.
      bbaf76f9
    • Ben Gamari's avatar
      Generate Typeable info at definition sites · bef2f03e
      Ben Gamari authored
      This patch implements the idea floated in Trac #9858, namely that we
      should generate type-representation information at the data type
      declaration site, rather than when solving a Typeable constraint.
      
      However, this turned out quite a bit harder than I expected. I still
      think it's the right thing to do, and it's done now, but it was quite
      a struggle.
      
      See particularly
      
       * Note [Grand plan for Typeable] in TcTypeable (which is a new module)
       * Note [The overall promotion story] in DataCon (clarifies existing stuff)
      
      The most painful bit was that to generate Typeable instances (ie
      TyConRepName bindings) for every TyCon is tricky for types in ghc-prim
      etc:
      
       * We need to have enough data types around to *define* a TyCon
       * Many of these types are wired-in
      
      Also, to minimise the code generated for each data type, I wanted to
      generate pure data, not CAFs with unpackCString# stuff floating about.
      
      Performance
      ~~~~~~~~~~~
      Three perf/compiler tests start to allocate quite a bit more. This isn't
      surprising, because they all allocate zillions of data types, with
      practically no other code, esp. T1969
      
       * T3294:   GHC allocates 110% more (filed #11030 to track this)
       * T1969:   GHC allocates 30% more
       * T4801:   GHC allocates 14% more
       * T5321FD: GHC allocates 13% more
       * T783:    GHC allocates 12% more
       * T9675:   GHC allocates 12% more
       * T5642:   GHC allocates 10% more
       * T9961:   GHC allocates 6% more
      
       * T9203:   Program allocates 54% less
      
      I'm treating this as acceptable. The payoff comes in Typeable-heavy
      code.
      
      Remaining to do
      ~~~~~~~~~~~~~~~
      
       * I think that "TyCon" and "Module" are over-generic names to use for
         the runtime type representations used in GHC.Typeable. Better might be
         "TrTyCon" and "TrModule". But I have not yet done this
      
       * Add more info the the "TyCon" e.g. source location where it was
         defined
      
       * Use the new "Module" type to help with Trac Trac #10068
      
       * It would be possible to generate TyConRepName (ie Typeable
         instances) selectively rather than all the time. We'd need to persist
         the information in interface files. Lacking a motivating reason I have
         not done this, but it would not be difficult.
      
      Refactoring
      ~~~~~~~~~~~
      As is so often the case, I ended up refactoring more than I intended.
      In particular
      
       * In TyCon, a type *family* (whether type or data) is repesented by a
         FamilyTyCon
           * a algebraic data type (including data/newtype instances) is
             represented by AlgTyCon This wasn't true before; a data family
             was represented as an AlgTyCon. There are some corresponding
             changes in IfaceSyn.
      
           * Also get rid of the (unhelpfully named) tyConParent.
      
       * In TyCon define 'Promoted', isomorphic to Maybe, used when things are
         optionally promoted; and use it elsewhere in GHC.
      
       * Cleanup handling of knownKeyNames
      
       * Each TyCon, including promoted TyCons, contains its TyConRepName, if
         it has one. This is, in effect, the name of its Typeable instance.
      
      Requires update of the haddock submodule.
      
      Differential Revision: https://phabricator.haskell.org/D757
      bef2f03e
  22. 16 Oct, 2015 1 commit
  23. 15 Oct, 2015 1 commit
  24. 22 Sep, 2015 1 commit
  25. 03 Sep, 2015 1 commit
  26. 20 Jul, 2015 1 commit
    • thomasw's avatar
      Support wild cards in TH splices · 49373ffe
      thomasw authored
      - Declaration splices: partial type signatures are fully supported in TH
        declaration splices.
      
        For example, the wild cards in the example below will unify with `Eq
      a`
        and `a -> a -> Bool`, as expected:
      
      ```
      [d| foo :: _ => _
          foo x y = x == y |]
      ```
      
      - Expression splices: anonymous and named wild cards are supported in
        expression signatures, but extra-constraints wild cards aren't. Just
        as is the case for regular expression signatures.
      
      ```
      [e | Just True :: _a _ |]
      ```
      
      - Typed expression splices: the same wildcards as in (untyped)
        expression splices are supported.
      
      - Pattern splices: TH doesn't support type signatures in pattern
        splices, consequently, partial type signatures aren't supported
        either.
      
      - Type splices: partial type signatures are only partially supported in
        type splices, specifically: only anonymous wild cards are allowed.
      
        So `[t| _ |]`, `[t| _ -> Maybe _ |]` will work, but `[t| _ => _ |]` or
        `[| _a |]` won't (without `-XNamedWildCards`, the latter will work as
        the named wild card is treated as a type variable).
      
        Normally, named wild cards are collected before renaming a (partial)
        type signature. However, TH type splices are run during renaming, i.e.
        after the initial traversal, leading to out of scope errors for named
        wild cards. We can't just extend the initial traversal to collect the
        named wild cards in TH type splices, as we'd need to expand them,
        which is supposed to happen only once, during renaming.
      
        Similarly, the extra-constraints wild card is handled right before
        renaming too, and is therefore also not supported in a TH type splice.
        Another reason not to support extra-constraints wild cards in TH type
        splices is that a single signature can contain many TH type splices,
        whereas it mustn't contain more than one extra-constraints wild card.
        Enforcing would this be hard the way things are currently organised.
      
        Anonymous wild cards pose no problem, because they start without names
        and are given names during renaming. These names are collected right
        after renaming. The names generated for anonymous wild cards in TH
        type splices will thus be collected as well.
      
        With a more invasive refactoring of the renaming, partial type
        signatures could be fully supported in TH type splices. As only
        anonymous wild cards have been requested so far, these small changes
        satisfying this request will do for now. Also don't forget that a TH
        declaration splices support all kinds of wild cards.
      
      - Extra-constraints wild cards were silently ignored in expression and
        pattern signatures, appropriate error messages are now generated.
      
      Test Plan: run new tests
      
      Reviewers: austin, goldfire, adamgundry, bgamari
      
      Reviewed By: goldfire, adamgundry, bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1048
      
      GHC Trac Issues: #10094, #10548
      49373ffe
  27. 16 Jul, 2015 1 commit
    • RyanGlScott's avatar
      Handle Char#, Addr# in TH quasiquoter (fixes #10620) · 2c9de9c9
      RyanGlScott authored
      DsMeta does not attempt to handle quasiquoted Char# or Addr# values,
      which causes expressions like `$([| 'a'# |])` or `$([| "abc"# |])` to
      fail
      with an `Exotic literal not (yet) handled by Template Haskell` error.
      
      To fix this, the API of `template-haskell` had to be changed so that
      `Lit`
      now has an extra constructor `CharPrimL` (a `StringPrimL` constructor
      already
      existed, but it wasn't used). In addition, `DsMeta` has to manipulate
      `CoreExpr`s directly that involve `Word8`s. In order to do this,
      `Word8` had
      to be added as a wired-in type to `TysWiredIn`.
      
      Actually converting from `HsCharPrim` and `HsStringPrim` to `CharPrimL`
      and
      `StringPrimL`, respectively, is pretty straightforward after that, since
      both `HsCharPrim` and `CharPrimL` use `Char` internally, and
      `HsStringPrim`
      uses a `ByteString` internally, which can easily be converted to
      `[Word8]`,
      which is what `StringPrimL` uses.
      
      Reviewers: goldfire, austin, simonpj, bgamari
      
      Reviewed By: simonpj, bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1054
      
      GHC Trac Issues: #10620
      2c9de9c9
  28. 18 May, 2015 1 commit
    • Simon Peyton Jones's avatar
      Refactor tuple constraints · ffc21506
      Simon Peyton Jones authored
      Make tuple constraints be handled by a perfectly ordinary
      type class, with the component constraints being the
      superclasses:
          class (c1, c2) => (c2, c2)
      
      This change was provoked by
      
        #10359  inability to re-use a given tuple
                constraint as a whole
      
        #9858   confusion between term tuples
                and constraint tuples
      
      but it's generally a very nice simplification. We get rid of
       -  In Type, the TuplePred constructor of PredTree,
          and all the code that dealt with TuplePreds
       -  In TcEvidence, the constructors EvTupleMk, EvTupleSel
      
      See Note [How tuples work] in TysWiredIn.
      
      Of course, nothing is ever entirely simple. This one
      proved quite fiddly.
      
      - I did quite a bit of renaming, which makes this patch
        touch a lot of modules. In partiuclar tupleCon -> tupleDataCon.
      
      - I made constraint tuples known-key rather than wired-in.
        This is different to boxed/unboxed tuples, but it proved
        awkward to have all the superclass selectors wired-in.
        Easier just to use the standard mechanims.
      
      - While I was fiddling with known-key names, I split the TH Name
        definitions out of DsMeta into a new module THNames.  That meant
        that the known-key names can all be gathered in PrelInfo, without
        causing module loops.
      
      - I found that the parser was parsing an import item like
            T( .. )
        as a *data constructor* T, and then using setRdrNameSpace to
        fix it.  Stupid!  So I changed the parser to parse a *type
        constructor* T, which means less use of setRdrNameSpace.
      
        I also improved setRdrNameSpace to behave better on Exact Names.
        Largely on priciple; I don't think it matters a lot.
      
      - When compiling a data type declaration for a wired-in thing like
        tuples (,), or lists, we don't really need to look at the
        declaration.  We have the wired-in thing!  And not doing so avoids
        having to line up the uniques for data constructor workers etc.
        See Note [Declarations for wired-in things]
      
      - I found that FunDeps.oclose wasn't taking superclasses into
        account; easily fixed.
      
      - Some error message refactoring for invalid constraints in TcValidity
      
      - Haddock needs to absorb the change too; so there is a submodule update
      ffc21506
  29. 14 May, 2015 1 commit
    • Austin Seipp's avatar
      Revert multiple commits · 3cf8ecdc
      Austin Seipp authored
      This reverts multiple commits from Simon:
      
        - 04a484ea Test Trac #10359
        - a9ccd37a Test Trac #10403
        - c0aae6f6 Test Trac #10248
        - eb6ca851 Make the "matchable-given" check happen first
        - ca173aa3 Add a case to checkValidTyCon
        - 51cbad15 Update haddock submodule
        - 6e1174da Separate transCloVarSet from fixVarSet
        - a8493e03 Fix imports in HscMain (stage2)
        - a154944b Two wibbles to fix the build
        - 5910a1bc Change in capitalisation of error msg
        - 130e93aa Refactor tuple constraints
        - 8da785d5 Delete commented-out line
      
      These break the build by causing Haddock to fail mysteriously when
      trying to examine GHC.Prim it seems.
      3cf8ecdc
  30. 13 May, 2015 1 commit
    • Simon Peyton Jones's avatar
      Refactor tuple constraints · 130e93aa
      Simon Peyton Jones authored
      Make tuple constraints be handled by a perfectly ordinary
      type class, with the component constraints being the
      superclasses:
          class (c1, c2) => (c2, c2)
      
      This change was provoked by
      
        #10359  inability to re-use a given tuple
                constraint as a whole
      
        #9858   confusion between term tuples
                and constraint tuples
      
      but it's generally a very nice simplification. We get rid of
       -  In Type, the TuplePred constructor of PredTree,
          and all the code that dealt with TuplePreds
       -  In TcEvidence, the constructors EvTupleMk, EvTupleSel
      
      See Note [How tuples work] in TysWiredIn.
      
      Of course, nothing is ever entirely simple. This one
      proved quite fiddly.
      
      - I did quite a bit of renaming, which makes this patch
        touch a lot of modules. In partiuclar tupleCon -> tupleDataCon.
      
      - I made constraint tuples known-key rather than wired-in.
        This is different to boxed/unboxed tuples, but it proved
        awkward to have all the superclass selectors wired-in.
        Easier just to use the standard mechanims.
      
      - While I was fiddling with known-key names, I split the TH Name
        definitions out of DsMeta into a new module THNames.  That meant
        that the known-key names can all be gathered in PrelInfo, without
        causing module loops.
      
      - I found that the parser was parsing an import item like
            T( .. )
        as a *data constructor* T, and then using setRdrNameSpace to
        fix it.  Stupid!  So I changed the parser to parse a *type
        constructor* T, which means less use of setRdrNameSpace.
      
        I also improved setRdrNameSpace to behave better on Exact Names.
        Largely on priciple; I don't think it matters a lot.
      
      - When compiling a data type declaration for a wired-in thing like
        tuples (,), or lists, we don't really need to look at the
        declaration.  We have the wired-in thing!  And not doing so avoids
        having to line up the uniques for data constructor workers etc.
        See Note [Declarations for wired-in things]
      
      - I found that FunDeps.oclose wasn't taking superclasses into
        account; easily fixed.
      
      - Some error message refactoring for invalid constraints in TcValidity
      130e93aa