1. 25 Jun, 2016 1 commit
    • eir@cis.upenn.edu's avatar
      s/Invisible/Inferred/g s/Visible/Required/g · 5fdb854c
      eir@cis.upenn.edu authored
      This renames VisibilityFlag from
      
      > data VisibilityFlag = Visible | Specified | Invisible
      
      to
      
      > data ArgFlag = Required | Specified | Inferred
      
      The old name was quite confusing, because both Specified
      and Invisible were invisible! The new names are hopefully clearer.
      5fdb854c
  2. 24 Jun, 2016 2 commits
    • Simon Peyton Jones's avatar
      Comments around invisibility · c871ce49
      Simon Peyton Jones authored
      Very minor
      c871ce49
    • Simon Peyton Jones's avatar
      Improve typechecking of instance defaults · d2958bd0
      Simon Peyton Jones authored
      In an instance declaration when you don't specify the code for a
      method, GHC fills in from the default binding in the class.
      The type of the default method can legitmiately be ambiguous ---
      see Note [Default methods in instances] in TcInstDcls --- so
      typechecking it can be tricky.
      
      Trac #12220 showed that although we were dealing with that ambiguity
      for /vanilla/ default methods, we were not doing so for /generic/
      default methods.  Moreover we were dealing with it clumsily, by
      generating post-typechecked code.
      
      This patch fixes the bug AND deletes code!  We now use the same code
      path for both vanilla and generic default methods; and generate
      /pre-typechecked/ code in both cases.  The key trick is that we can use
      Visible Type Application to deal with the ambiguity, which wasn't
      possible before.  Hooray.
      
      There is a small hit to performance in compiler/perf/T1969 which
      consists of nothing BUT instance declarations with several default
      methods to fill, which we now have to typecheck. The actual hit is
      from 724 -> 756 or 4% in that extreme example.  Real world programs
      have vastly fewer instance decls.
      d2958bd0
  3. 15 Jun, 2016 2 commits
    • Simon Peyton Jones's avatar
      Major patch to introduce TyConBinder · e368f326
      Simon Peyton Jones authored
      Before this patch, following the TypeInType innovations,
      each TyCon had two lists:
        - tyConBinders :: [TyBinder]
        - tyConTyVars  :: [TyVar]
      
      They were in 1-1 correspondence and contained
      overlapping information.  More broadly, there were many
      places where we had to pass around this pair of lists,
      instead of a single list.
      
      This commit tidies all that up, by having just one list of
      binders in a TyCon:
      
        - tyConBinders :: [TyConBinder]
      
      The new data types look like this:
      
        Var.hs:
           data TyVarBndr tyvar vis = TvBndr tyvar vis
           data VisibilityFlag = Visible | Specified | Invisible
           type TyVarBinder = TyVarBndr TyVar VisibilityFlag
      
        TyCon.hs:
           type TyConBinder = TyVarBndr TyVar TyConBndrVis
      
           data TyConBndrVis
             = NamedTCB VisibilityFlag
             | AnonTCB
      
        TyCoRep.hs:
           data TyBinder
             = Named TyVarBinder
             | Anon Type
      
      Note that Var.TyVarBdr has moved from TyCoRep and has been
      made polymorphic in the tyvar and visiblity fields:
      
           type TyVarBinder = TyVarBndr TyVar VisibilityFlag
              -- Used in ForAllTy
           type TyConBinder = TyVarBndr TyVar TyConBndrVis
              -- Used in TyCon
      
           type IfaceForAllBndr  = TyVarBndr IfaceTvBndr VisibilityFlag
           type IfaceTyConBinder = TyVarBndr IfaceTvBndr TyConBndrVis
               -- Ditto, in interface files
      
      There are a zillion knock-on changes, but everything
      arises from these types.  It was a bit fiddly to get the
      module loops to work out right!
      
      Some smaller points
      ~~~~~~~~~~~~~~~~~~~
      * Nice new functions
          TysPrim.mkTemplateKiTyVars
          TysPrim.mkTemplateTyConBinders
        which help you make the tyvar binders for dependently-typed
        TyCons.  See comments with their definition.
      
      * The change showed up a bug in TcGenGenerics.tc_mkRepTy, where the code
        was making an assumption about the order of the kind variables in the
        kind of GHC.Generics.(:.:).  I fixed this; see TcGenGenerics.mkComp.
      e368f326
    • Simon Peyton Jones's avatar
      Re-add FunTy (big patch) · 77bb0927
      Simon Peyton Jones authored
      With TypeInType Richard combined ForAllTy and FunTy, but that was often
      awkward, and yielded little benefit becuase in practice the two were
      always treated separately.  This patch re-introduces FunTy.  Specfically
      
      * New type
          data TyVarBinder = TvBndr TyVar VisibilityFlag
        This /always/ has a TyVar it.  In many places that's just what
        what we want, so there are /lots/ of TyBinder -> TyVarBinder changes
      
      * TyBinder still exists:
          data TyBinder = Named TyVarBinder | Anon Type
      
      * data Type = ForAllTy TyVarBinder Type
                  | FunTy Type Type
                  |  ....
      
      There are a LOT of knock-on changes, but they are all routine.
      
      The Haddock submodule needs to be updated too
      77bb0927
  4. 21 Mar, 2016 1 commit
    • eir@cis.upenn.edu's avatar
      Track specified/invisible more carefully. · 35e93797
      eir@cis.upenn.edu authored
      In particular, this allows correct tracking of specified/invisible
      for variables in Haskell98 data constructors and in pattern synonyms.
      GADT-syntax constructors are harder, and are left until #11721.
      
      This was all inspired by Simon's comments to my fix for #11512,
      which this subsumes.
      
      Test case: ghci/scripts/TypeAppData
      
      [skip ci]  (The test case fails because of an unrelated problem
      fixed in the next commit.)
      35e93797
  5. 05 Mar, 2016 1 commit
    • Rik Steenkamp's avatar
      Fix printing of an `IfacePatSyn` · 3801262e
      Rik Steenkamp authored
      Now the existentially quantified type variables are printed
      at the correct location when printing a pattern synonym type
      from an `IfacePatSyn`. The function `pprIfaceContextMaybe`
      has been removed as it is no longer needed.
      
      Fixes #11524.
      
      Reviewers: austin, goldfire, thomie, bgamari, mpickering
      
      Reviewed By: bgamari
      
      Differential Revision: https://phabricator.haskell.org/D1958
      
      GHC Trac Issues: #11524
      3801262e
  6. 24 Feb, 2016 1 commit
    • eir@cis.upenn.edu's avatar
      Address #11471 by putting RuntimeRep in kinds. · d8c64e86
      eir@cis.upenn.edu authored
      See Note [TYPE] in TysPrim. There are still some outstanding
      pieces in #11471 though, so this doesn't actually nail the bug.
      
      This commit also contains a few performance improvements:
      
      * Short-cut equality checking of nullary type syns
      
      * Compare types before kinds in eqType
      
      * INLINE coreViewOneStarKind
      
      * Store tycon binders separately from kinds.
      
      This resulted in a ~10% performance improvement in compiling
      the Cabal package. No change in functionality other than
      performance. (This affects the interface file format, though.)
      
      This commit updates the haddock submodule.
      d8c64e86
  7. 18 Feb, 2016 1 commit
    • Simon Peyton Jones's avatar
      (Another) minor refactoring of substitutions · b5292557
      Simon Peyton Jones authored
      No change in functionality here, but greater clarity:
      
      * In FamInstEnv.FlattenEnv, kill off the fi_in_scope field
        We are already maintaining an in-scope set in the fe_subst field,
        so it's silly do to it twice.
      
        (This isn't strictly connected to the rest of this patch, but
        the nomenclature changes below affect the same code, so I put
        them together.)
      
      * TyCoRep.extendTCVSubst used to take a TyVar or a CoVar and work
        out what to do, but in fact we almost always know which of the
        two we are doing.  So:
          - define extendTvSubst, extendCvSubst
          - and use them
      
      * Similar renamings in TyCoRep:
         - extendTCvSubstList        -->   extendTvSubstList
         - extendTCvSubstBinder      -->   extendTvSubstBinder
         - extendTCvSubstAndInScope  --> extendTvSubstAndInScope
      
      * Add Type.extendTvSubstWithClone, extendCvSubstWithClone
      
      * Similar nomenclature changes in Subst, SimplEnv, Specialise
      
      * Kill off TyCoRep.substTelescope (never used)
      b5292557
  8. 18 Jan, 2016 2 commits
    • Jan Stolarek's avatar
      Replace calls to `ptext . sLit` with `text` · b8abd852
      Jan Stolarek authored
      Summary:
      In the past the canonical way for constructing an SDoc string literal was the
      composition `ptext . sLit`.  But for some time now we have function `text` that
      does the same.  Plus it has some rules that optimize its runtime behaviour.
      This patch takes all uses of `ptext . sLit` in the compiler and replaces them
      with calls to `text`.  The main benefits of this patch are clener (shorter) code
      and less dependencies between module, because many modules now do not need to
      import `FastString`.  I don't expect any performance benefits - we mostly use
      SDocs to report errors and it seems there is little to be gained here.
      
      Test Plan: ./validate
      
      Reviewers: bgamari, austin, goldfire, hvr, alanz
      
      Subscribers: goldfire, thomie, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D1784
      b8abd852
    • Eric Seidel's avatar
      un-wire-in error, undefined, CallStack, and IP · a7b751db
      Eric Seidel authored
      I missed a crucial step in the wiring-in process of `CallStack` in D861,
      the bit where you actually wire-in the Name... This led to a nasty bug
      where GHC thought `CallStack` was not wired-in and tried to fingerprint
      it, which failed because the defining module was not loaded.
      
      But we don't need `CallStack` to be wired-in anymore since `error` and
      `undefined` no longer need to be wired-in. So we just remove them all.
      
      Updates haddock submodule.
      
      Test Plan: `./validate` and `make slowtest TEST=tc198`
      
      Reviewers: simonpj, goldfire, austin, hvr, bgamari
      
      Reviewed By: simonpj, bgamari
      
      Subscribers: goldfire, thomie
      
      Projects: #ghc
      
      Differential Revision: https://phabricator.haskell.org/D1739
      
      GHC Trac Issues: #11331
      a7b751db
  9. 24 Dec, 2015 1 commit
    • eir@cis.upenn.edu's avatar
      Visible type application · 2db18b81
      eir@cis.upenn.edu authored
      This re-working of the typechecker algorithm is based on
      the paper "Visible type application", by Richard Eisenberg,
      Stephanie Weirich, and Hamidhasan Ahmed, to be published at
      ESOP'16.
      
      This patch introduces -XTypeApplications, which allows users
      to say, for example `id @Int`, which has type `Int -> Int`. See
      the changes to the user manual for details.
      
      This patch addresses tickets #10619, #5296, #10589.
      2db18b81
  10. 17 Dec, 2015 1 commit
  11. 11 Dec, 2015 1 commit
    • eir@cis.upenn.edu's avatar
      Add kind equalities to GHC. · 67465497
      eir@cis.upenn.edu authored
      This implements the ideas originally put forward in
      "System FC with Explicit Kind Equality" (ICFP'13).
      
      There are several noteworthy changes with this patch:
       * We now have casts in types. These change the kind
         of a type. See new constructor `CastTy`.
      
       * All types and all constructors can be promoted.
         This includes GADT constructors. GADT pattern matches
         take place in type family equations. In Core,
         types can now be applied to coercions via the
         `CoercionTy` constructor.
      
       * Coercions can now be heterogeneous, relating types
         of different kinds. A coercion proving `t1 :: k1 ~ t2 :: k2`
         proves both that `t1` and `t2` are the same and also that
         `k1` and `k2` are the same.
      
       * The `Coercion` type has been significantly enhanced.
         The documentation in `docs/core-spec/core-spec.pdf` reflects
         the new reality.
      
       * The type of `*` is now `*`. No more `BOX`.
      
       * Users can write explicit kind variables in their code,
         anywhere they can write type variables. For backward compatibility,
         automatic inference of kind-variable binding is still permitted.
      
       * The new extension `TypeInType` turns on the new user-facing
         features.
      
       * Type families and synonyms are now promoted to kinds. This causes
         trouble with parsing `*`, leading to the somewhat awkward new
         `HsAppsTy` constructor for `HsType`. This is dispatched with in
         the renamer, where the kind `*` can be told apart from a
         type-level multiplication operator. Without `-XTypeInType` the
         old behavior persists. With `-XTypeInType`, you need to import
         `Data.Kind` to get `*`, also known as `Type`.
      
       * The kind-checking algorithms in TcHsType have been significantly
         rewritten to allow for enhanced kinds.
      
       * The new features are still quite experimental and may be in flux.
      
       * TODO: Several open tickets: #11195, #11196, #11197, #11198, #11203.
      
       * TODO: Update user manual.
      
      Tickets addressed: #9017, #9173, #7961, #10524, #8566, #11142.
      Updates Haddock submodule.
      67465497
  12. 25 Nov, 2015 1 commit
    • Simon Peyton Jones's avatar
      Refactor default methods (Trac #11105) · 924f8517
      Simon Peyton Jones authored
      This patch does some signficant refactoring to the treatment
      of default methods in class declarations, and more generally
      to the type checking of type/class decls.
      
      Highlights:
      
      * When the class has a generic-default method, such as
           class C a where
             op :: a -> a -> Bool
             default op :: Ord a => a -> a -> a
        the ClassOpItem records the type of the generic-default,
        in this case the type (Ord a => a -> a -> a)
      
      * I killed off Class.DefMeth in favour of the very-similar
        BasicTypes.DefMethSpec.  However it turned out to be better
        to use a Maybe, thus
            Maybe (DefMethSpec Type)
        with Nothing meaning "no default method".
      
      * In TcTyClsDecls.tcTyClGroup, we used to accumulate a [TyThing],
        but I found a way to make it much simpler, accumulating only
        a [TyCon].  Much less wrapping and unwrapping.
      
      * On the way I also fixed Trac #10896 in a better way. Instead
        of killing off all ambiguity checks whenever there are any type
        errors (the fix in commit 8e8b9ed9), I instead recover in
        TcTyClsDecls.checkValidTyCl.
      
      There was a lot of associated simplification all round
      924f8517
  13. 02 Sep, 2015 1 commit
    • Eric Seidel's avatar
      Use IP based CallStack in error and undefined · 6740d70d
      Eric Seidel authored
      This patch modifies `error`, `undefined`, and `assertError` to use
      implicit call-stacks to provide better error messages to users.
      
      There are a few knock-on effects:
      
      - `GHC.Classes.IP` is now wired-in so it can be used in the wired-in
        types for `error` and `undefined`.
      
      - `TysPrim.tyVarList` has been replaced with a new function
        `TysPrim.mkTemplateTyVars`. `tyVarList` made it easy to introduce
        subtle bugs when you need tyvars of different kinds. The naive
      
        ```
        tv1 = head $ tyVarList kind1
        tv2 = head $ tyVarList kind2
        ```
      
        would result in `tv1` and `tv2` sharing a `Unique`, thus substitutions
        would be applied incorrectly, treating `tv1` and `tv2` as the same
        tyvar. `mkTemplateTyVars` avoids this pitfall by taking a list of kinds
        and producing a single tyvar of each kind.
      
      - The types `GHC.SrcLoc.SrcLoc` and `GHC.Stack.CallStack` now live in
        ghc-prim.
      
      - The type `GHC.Exception.ErrorCall` has a new constructor
        `ErrorCallWithLocation` that takes two `String`s instead of one, the
        2nd one being arbitrary metadata about the error (but usually the
        call-stack). A bi-directional pattern synonym `ErrorCall` continues to
        provide the old API.
      
      Updates Cabal, array, and haddock submodules.
      
      Reviewers: nh2, goldfire, simonpj, hvr, rwbarton, austin, bgamari
      
      Reviewed By: simonpj
      
      Subscribers: rwbarton, rodlogic, goldfire, maoe, simonmar, carter,
      liyang, bgamari, thomie
      
      Differential Revision: https://phabricator.haskell.org/D861
      
      GHC Trac Issues: #5273
      6740d70d
  14. 22 Jul, 2015 1 commit
  15. 20 May, 2015 1 commit
  16. 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
  17. 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
  18. 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
  19. 01 May, 2015 1 commit
    • Simon Peyton Jones's avatar
      Refactor TyCon to eliminate TupleTyCon · f6ab0f2d
      Simon Peyton Jones authored
      This makes TupleTyCon into an ordinary AlgTyCon, distinguished
      by its AlgTyConRhs, rather than a separate constructor of TyCon.
      
      It is preparatory work for making constraint tuples into classes,
      for which the ConstraintTuple tuples will have a TyConParent
      of a ClassTyCon.  Tuples didn't have this possiblity before.
      
      The patch affects other modules because I eliminated the
      unsatisfactory partial functions tupleTyConBoxity and tupleTyConSort.
      And tupleTyConArity which is just tyConArity.
      f6ab0f2d
  20. 04 Mar, 2015 1 commit
  21. 10 Feb, 2015 1 commit
  22. 18 Dec, 2014 1 commit
    • Iavor S. Diatchki's avatar
      Add a provenance field to universal coercions. · 1d4e94d1
      Iavor S. Diatchki authored
      Universal coercions allow casting between arbitrary types, so it is a
      good idea to keep track where they came from, which now we can do by
      using the provenance field in `UnivCo`.
      
      This is also handy for type-checker plugins that provide functionality
      beyond what's expressible by GHC's standard coercions:  such plugins
      can generate universal coercions, but they should still tag them,
      so that if something goes wrong we can link the casts to the plugin.
      1d4e94d1
  23. 03 Dec, 2014 1 commit
  24. 20 Nov, 2014 1 commit
    • cactus's avatar
      Add support for pattern synonym type signatures. · cce6318e
      cactus authored
      Syntax is of the form
      
          pattern P :: (Prov b) => (Req a) => a -> b -> Int -> T a
      
      which declares a pattern synonym called `P`, with argument types `a`, `b`,
      and `Int`, and result type `T a`, with provided context `(Prov b)` and required
      context `(Req a)`.
      
      The Haddock submodule is also updated to use this new syntax in generated docs.
      cce6318e
  25. 02 Nov, 2014 1 commit
  26. 03 Jun, 2014 2 commits
    • Simon Peyton Jones's avatar
      Use IfLclName instead of OccName in IfaceEqSpec · 6e8861c9
      Simon Peyton Jones authored
      The type variables in the IfaceEqSpec of a data constructor are really
      ordinarly *occurrences*, so they should be IfLclNames just like any
      other type variable occurence.
      6e8861c9
    • Simon Peyton Jones's avatar
      Do pretty-printing of TyThings via IfaceDecl (Trac #7730) · b4856f9f
      Simon Peyton Jones authored
      All the initial work on this was done fy 'archblob' (fcsernik@gmail.com);
      thank you!
      
      I reviewed the patch, started some tidying, up and then ended up in a huge
      swamp of changes, not all of which I can remember now.  But:
      
      * To suppress kind arguments when we have -fno-print-explicit-kinds,
          - IfaceTyConApp argument types are in a tagged list IfaceTcArgs
      
      * To allow overloaded types to be printed with =>, add IfaceDFunTy to IfaceType.
      
      * When printing data/type family instances for the user, I've made them
        print out an informative RHS, which is a new feature. Thus
              ghci> info T
              data family T a
              data instance T Int = T1 Int Int
              data instance T Bool = T2
      
      * In implementation terms, pprIfaceDecl has just one "context" argument,
        of type IfaceSyn.ShowSub, which says
             - How to print the binders of the decl
               see note [Printing IfaceDecl binders] in IfaceSyn
             - Which sub-comoponents (eg constructors) to print
      
      * Moved FastStringEnv from RnEnv to OccName
      
      It all took a ridiculously long time to do.  But it's done!
      b4856f9f
  27. 14 Mar, 2014 1 commit
  28. 13 Mar, 2014 1 commit
  29. 18 Sep, 2013 1 commit
    • eir@cis.upenn.edu's avatar
      Change role annotation syntax. · f4046b50
      eir@cis.upenn.edu authored
      This fixes bugs #8185, #8234, and #8246. The new syntax is explained
      in the comments to #8185, appears in the "Roles" subsection of the
      manual, and on the [wiki:Roles] wiki page.
      
      This change also removes the ability for a role annotation on type
      synonyms, as noted in #8234.
      f4046b50
  30. 13 Sep, 2013 1 commit
    • Iavor S. Diatchki's avatar
      Add support for evaluation of type-level natural numbers. · 1f77a534
      Iavor S. Diatchki authored
      This patch implements some simple evaluation of type-level expressions
      featuring natural numbers.  We can evaluate *concrete* expressions that
      use the built-in type families (+), (*), (^), and (<=?), declared in
      GHC.TypeLits.   We can also do some type inference involving these
      functions.  For example, if we encounter a constraint such as `(2 + x) ~ 5`
      we can infer that `x` must be 3.  Note, however, this is used only to
      resolve unification variables (i.e., as a form of a constraint improvement)
      and not to generate new facts.  This is similar to how functional
      dependencies work in GHC.
      
      The patch adds a new form of coercion, `AxiomRuleCo`, which makes use
      of a new form of axiom called `CoAxiomRule`.  This is the form of evidence
      generate when we solve a constraint, such as `(1 + 2) ~ 3`.
      
      The patch also adds support for built-in type-families, by adding a new
      form of TyCon rhs: `BuiltInSynFamTyCon`.  such built-in type-family
      constructors contain a record with functions that are used by the
      constraint solver to simplify and improve constraints involving the
      built-in function (see `TcInteract`).  The record in defined in `FamInst`.
      
      The type constructors and rules for evaluating the type-level functions
      are in a new module called `TcTypeNats`.
      1f77a534
  31. 02 Aug, 2013 1 commit
  32. 27 Jul, 2013 1 commit
  33. 21 Jun, 2013 1 commit
    • eir@cis.upenn.edu's avatar
      Revise implementation of overlapping type family instances. · 569b2652
      eir@cis.upenn.edu authored
      This commit changes the syntax and story around overlapping type
      family instances. Before, we had "unbranched" instances and
      "branched" instances. Now, we have closed type families and
      open ones.
      
      The behavior of open families is completely unchanged. In particular,
      coincident overlap of open type family instances still works, despite
      emails to the contrary.
      
      A closed type family is declared like this:
      > type family F a where
      >   F Int = Bool
      >   F a   = Char
      The equations are tried in order, from top to bottom, subject to
      certain constraints, as described in the user manual. It is not
      allowed to declare an instance of a closed family.
      569b2652
  34. 22 Dec, 2012 1 commit
    • eir@cis.upenn.edu's avatar
      Implement overlapping type family instances. · 8366792e
      eir@cis.upenn.edu authored
      An ordered, overlapping type family instance is introduced by 'type
      instance
      where', followed by equations. See the new section in the user manual
      (7.7.2.2) for details. The canonical example is Boolean equality at the
      type
      level:
      
      type family Equals (a :: k) (b :: k) :: Bool
      type instance where
        Equals a a = True
        Equals a b = False
      
      A branched family instance, such as this one, checks its equations in
      order
      and applies only the first the matches. As explained in the note
      [Instance
      checking within groups] in FamInstEnv.lhs, we must be careful not to
      simplify,
      say, (Equals Int b) to False, because b might later unify with Int.
      
      This commit includes all of the commits on the overlapping-tyfams
      branch. SPJ
      requested that I combine all my commits over the past several months
      into one
      monolithic commit. The following GHC repos are affected: ghc, testsuite,
      utils/haddock, libraries/template-haskell, and libraries/dph.
      
      Here are some details for the interested:
      
      - The definition of CoAxiom has been moved from TyCon.lhs to a
        new file CoAxiom.lhs. I made this decision because of the
        number of definitions necessary to support BranchList.
      
      - BranchList is a GADT whose type tracks whether it is a
        singleton list or not-necessarily-a-singleton-list. The reason
        I introduced this type is to increase static checking of places
        where GHC code assumes that a FamInst or CoAxiom is indeed a
        singleton. This assumption takes place roughly 10 times
        throughout the code. I was worried that a future change to GHC
        would invalidate the assumption, and GHC might subtly fail to
        do the right thing. By explicitly labeling CoAxioms and
        FamInsts as being Unbranched (singleton) or
        Branched (not-necessarily-singleton), we make this assumption
        explicit and checkable. Furthermore, to enforce the accuracy of
        this label, the list of branches of a CoAxiom or FamInst is
        stored using a BranchList, whose constructors constrain its
        type index appropriately.
      
      I think that the decision to use BranchList is probably the most
      controversial decision I made from a code design point of view.
      Although I provide conversions to/from ordinary lists, it is more
      efficient to use the brList... functions provided in CoAxiom than
      always to convert. The use of these functions does not wander far
      from the core CoAxiom/FamInst logic.
      
      BranchLists are motivated and explained in the note [Branched axioms] in
      CoAxiom.lhs.
      
      - The CoAxiom type has changed significantly. You can see the new
        type in CoAxiom.lhs. It uses a CoAxBranch type to track
        branches of the CoAxiom. Correspondingly various functions
        producing and consuming CoAxioms had to change, including the
        binary layout of interface files.
      
      - To get branched axioms to work correctly, it is important to have a
        notion
        of type "apartness": two types are apart if they cannot unify, and no
        substitution of variables can ever get them to unify, even after type
      family
        simplification. (This is different than the normal failure to unify
      because
        of the type family bit.) This notion in encoded in tcApartTys, in
      Unify.lhs.
        Because apartness is finer-grained than unification, the tcUnifyTys
      now
        calls tcApartTys.
      
      - CoreLinting axioms has been updated, both to reflect the new
        form of CoAxiom and to enforce the apartness rules of branch
        application. The formalization of the new rules is in
        docs/core-spec/core-spec.pdf.
      
      - The FamInst type (in types/FamInstEnv.lhs) has changed
        significantly, paralleling the changes to CoAxiom. Of course,
        this forced minor changes in many files.
      
      - There are several new Notes in FamInstEnv.lhs, including one
        discussing confluent overlap and why we're not doing it.
      
      - lookupFamInstEnv, lookupFamInstEnvConflicts, and
        lookup_fam_inst_env' (the function that actually does the work)
        have all been more-or-less completely rewritten. There is a
        Note [lookup_fam_inst_env' implementation] describing the
        implementation. One of the changes that affects other files is
        to change the type of matches from a pair of (FamInst, [Type])
        to a new datatype (which now includes the index of the matching
        branch). This seemed a better design.
      
      - The TySynInstD constructor in Template Haskell was updated to
        use the new datatype TySynEqn. I also bumped the TH version
        number, requiring changes to DPH cabal files. (That's why the
        DPH repo has an overlapping-tyfams branch.)
      
      - As SPJ requested, I refactored some of the code in HsDecls:
      
       * splitting up TyDecl into SynDecl and DataDecl, correspondingly
         changing HsTyDefn to HsDataDefn (with only one constructor)
      
       * splitting FamInstD into TyFamInstD and DataFamInstD and
         splitting FamInstDecl into DataFamInstDecl and TyFamInstDecl
      
       * making the ClsInstD take a ClsInstDecl, for parallelism with
         InstDecl's other constructors
      
       * changing constructor TyFamily into FamDecl
      
       * creating a FamilyDecl type that stores the details for a family
         declaration; this is useful because FamilyDecls can appear in classes
      but
         other decls cannot
      
       * restricting the associated types and associated type defaults for a
       * class
         to be the new, more restrictive types
      
       * splitting cid_fam_insts into cid_tyfam_insts and cid_datafam_insts,
         according to the new types
      
       * perhaps one or two more that I'm overlooking
      
      None of these changes has far-reaching implications.
      
      - The user manual, section 7.7.2.2, is updated to describe the new type
        family
        instances.
      8366792e
  35. 05 Dec, 2012 1 commit
  36. 26 Nov, 2012 1 commit