1. 14 Nov, 2015 1 commit
  2. 13 Nov, 2015 1 commit
    • Alan Zimmerman's avatar
      APIAnnotations:add Locations in hsSyn for layout · 2290c8bd
      Alan Zimmerman authored
      Summary:
      At the moment ghc-exactprint, which uses the GHC API Annotations to
      provide a framework for roundtripping Haskell source code with optional
      AST edits, has to implement a horrible workaround to manage the points
      where layout needs to be captured.
      
      These are
      
          MatchGroup
          HsDo
          HsCmdDo
          HsLet
          LetStmt
          HsCmdLet
          GRHSs
      
      To provide a more natural representation, the contents subject to layout
      rules need to be wrapped in a SrcSpan.
      
      This commit does this.
      
      Trac ticket #10250
      
      Test Plan: ./validate
      
      Reviewers: hvr, goldfire, bgamari, austin, mpickering
      
      Reviewed By: mpickering
      
      Subscribers: thomie, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D1370
      
      GHC Trac Issues: #10250
      2290c8bd
  3. 11 Nov, 2015 1 commit
    • Alan Zimmerman's avatar
      Remove fun_infix from Funbind, as it is now in Match · f0f9365f
      Alan Zimmerman authored
      One of the changes D538 introduced is to add `m_fun_id_infix` to `Match`
      
      ```lang=hs
      data Match id body
        = Match {
              m_fun_id_infix :: (Maybe (Located id,Bool)),
                -- fun_id and fun_infix for functions with multiple equations
                -- only present for a RdrName. See note [fun_id in Match]
              m_pats :: [LPat id], -- The patterns
              m_type :: (Maybe (LHsType id)),
                                       -- A type signature for the result of the match
                                       -- Nothing after typechecking
              m_grhss :: (GRHSs id body)
        } deriving (Typeable)
      ```
      
      This was done to track the individual locations and fixity of the
      `fun_id` for each of the defining equations for a function when there
      are more than one.
      
      For example, the function `(&&&)` is defined with some prefix and some
      infix equations below.
      
      ```lang=hs
          (&&&  ) [] [] =  []
          xs    &&&   [] =  xs
          (  &&&  ) [] ys =  ys
      ```
      
      This means that the fun_infix is now superfluous in the `FunBind`. This
      has not been removed as a potentially risky change just before 7.10 RC2,
      and so must be done after.
      
      This ticket captures that task, which includes processing these fields
      through the renamer and beyond.
      
      Ticket #9988 introduced these fields into `Match` through renaming, this
      ticket it to continue through type checking and then remove it from
      `FunBind` completely.
      
      The split happened so that #9988 could land in 7.10
      
      Trac ticket : #10061
      
      Test Plan: ./validate
      
      Reviewers: goldfire, austin, simonpj, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: simonpj, thomie, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D1285
      
      GHC Trac Issues: #10061
      f0f9365f
  4. 07 Nov, 2015 1 commit
  5. 30 Oct, 2015 2 commits
    • 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
    • Adam Gundry's avatar
      Disambiguate record selectors by type signature · 0a163741
      Adam Gundry authored
      This makes DuplicateRecordFields more liberal in when it will
      accept ambiguous record selectors, making use of type information in a
      similar way to updates. See Note [Disambiguating record fields] for more
      details. I've also refactored how record updates are disambiguated.
      
      Test Plan: New and amended tests in overloadedrecflds
      
      Reviewers: simonpj, goldfire, bgamari, austin
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1391
      0a163741
  6. 29 Oct, 2015 3 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
    • Matthew Pickering's avatar
      Record pattern synonyms · 2a74a64e
      Matthew Pickering authored
      This patch implements an extension to pattern synonyms which allows user
      to specify pattern synonyms using record syntax. Doing so generates
      appropriate selectors and update functions.
      
      === Interaction with Duplicate Record Fields ===
      
      The implementation given here isn't quite as general as it could be with
      respect to the recently-introduced `DuplicateRecordFields` extension.
      
      Consider the following module:
      
          {-# LANGUAGE DuplicateRecordFields #-}
          {-# LANGUAGE PatternSynonyms #-}
      
          module Main where
      
          pattern S{a, b} = (a, b)
          pattern T{a}    = Just a
      
          main = do
            print S{ a = "fst", b = "snd" }
            print T{ a = "a" }
      
      In principle, this ought to work, because there is no ambiguity. But at
      the moment it leads to a "multiple declarations of a" error. The problem
      is that pattern synonym record selectors don't do the same name mangling
      as normal datatypes when DuplicateRecordFields is enabled. They could,
      but this would require some work to track the field label and selector
      name separately.
      
      In particular, we currently represent datatype selectors in the third
      component of AvailTC, but pattern synonym selectors are just represented
      as Avails (because they don't have a corresponding type constructor).
      Moreover, the GlobalRdrElt for a selector currently requires it to have
      a parent tycon.
      
      (example due to Adam Gundry)
      
      === Updating Explicitly Bidirectional Pattern Synonyms ===
      
      Consider the following
      
      ```
      pattern Silly{a} <- [a] where
        Silly a = [a, a]
      
      f1 = a [5] -- 5
      
      f2 = [5] {a = 6} -- currently [6,6]
      ```
      
      === Fixing Polymorphic Updates ===
      
      They were fixed by adding these two lines in `dsExpr`. This might break
      record updates but will be easy to fix.
      
      ```
      + ; let req_wrap = mkWpTyApps (mkTyVarTys univ_tvs)
      
      - , pat_wrap = idHsWrapper }
      +, pat_wrap = req_wrap }
      ```
      
      === Mixed selectors error ===
      
      Note [Mixed Record Field Updates]
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      
      Consider the following pattern synonym.
      
          data MyRec = MyRec { foo :: Int, qux :: String }
      
          pattern HisRec{f1, f2} = MyRec{foo = f1, qux=f2}
      
      This allows updates such as the following
      
          updater :: MyRec -> MyRec
          updater a = a {f1 = 1 }
      
      It would also make sense to allow the following update (which we
      reject).
      
          updater a = a {f1 = 1, qux = "two" } ==? MyRec 1 "two"
      
      This leads to confusing behaviour when the selectors in fact refer the
      same field.
      
          updater a = a {f1 = 1, foo = 2} ==? ???
      
      For this reason, we reject a mixture of pattern synonym and normal
      record selectors in the same update block. Although of course we still
      allow the following.
      
          updater a = (a {f1 = 1}) {foo = 2}
      
          > updater (MyRec 0 "str")
          MyRec 2 "str"
      2a74a64e
  7. 17 Oct, 2015 1 commit
    • Herbert Valerio Riedel's avatar
      Make Monad/Applicative instances MRP-friendly · e8ed2136
      Herbert Valerio Riedel authored
      This patch refactors pure/(*>) and return/(>>) in MRP-friendly way, i.e.
      such that the explicit definitions for `return` and `(>>)` match the
      MRP-style default-implementation, i.e.
      
        return = pure
      
      and
      
        (>>) = (*>)
      
      This way, e.g. all `return = pure` definitions can easily be grepped and
      removed in GHC 8.1;
      
      Test Plan: Harbormaster
      
      Reviewers: goldfire, alanz, bgamari, quchen, austin
      
      Reviewed By: quchen, austin
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1312
      e8ed2136
  8. 16 Oct, 2015 2 commits
    • Jan Stolarek's avatar
      Add typed holes support in Template Haskell. · 75492e74
      Jan Stolarek authored
      Fixes #10267. Typed holes in typed Template Haskell currently don't work.
      See #10945 and #10946.
      75492e74
    • Adam Gundry's avatar
      Implement DuplicateRecordFields · b1884b0e
      Adam Gundry authored
      This implements DuplicateRecordFields, the first part of the
      OverloadedRecordFields extension, as described at
      https://ghc.haskell.org/trac/ghc/wiki/Records/OverloadedRecordFields/DuplicateRecordFields
      
      This includes fairly wide-ranging changes in order to allow multiple
      records within the same module to use the same field names.  Note that
      it does *not* allow record selector functions to be used if they are
      ambiguous, and it does not have any form of type-based disambiguation
      for selectors (but it does for updates). Subsequent parts will make
      overloading selectors possible using orthogonal extensions, as
      described on the wiki pages.  This part touches quite a lot of the
      codebase, and requires changes to several GHC API datatypes in order
      to distinguish between field labels (which may be overloaded) and
      selector function names (which are always unique).
      
      The Haddock submodule has been adapted to compile with the GHC API
      changes, but it will need further work to properly support modules
      that use the DuplicateRecordFields extension.
      
      Test Plan: New tests added in testsuite/tests/overloadedrecflds; these
      will be extended once the other parts are implemented.
      
      Reviewers: goldfire, bgamari, simonpj, austin
      
      Subscribers: sjcjoosten, haggholm, mpickering, bgamari, tibbe, thomie,
      goldfire
      
      Differential Revision: https://phabricator.haskell.org/D761
      b1884b0e
  9. 15 Oct, 2015 1 commit
  10. 08 Oct, 2015 1 commit
  11. 03 Oct, 2015 1 commit
  12. 02 Oct, 2015 1 commit
    • Ben Gamari's avatar
      Fix treatment of -0.0 · eb975d2e
      Ben Gamari authored
      Here we fix a few mis-optimizations that could occur in code with
      floating point comparisons with -0.0. These issues arose from our
      insistence on rewriting equalities into case analyses and the
      simplifier's ignorance of floating-point semantics.
      
      For instance, in Trac #10215 (and the similar issue Trac #9238) we
      turned `ds == 0.0` into a case analysis,
      
      ```
      case ds of
          __DEFAULT -> ...
          0.0 -> ...
      ```
      
      Where the second alternative matches where `ds` is +0.0 and *also* -0.0.
      However, the simplifier doesn't realize this and will introduce a local
      inlining of `ds = -- +0.0` as it believes this is the only
      value that matches this pattern.
      
      Instead of teaching the simplifier about floating-point semantics
      we simply prohibit case analysis on floating-point scrutinees and keep
      this logic in the comparison primops, where it belongs.
      
      We do several things here,
      
       - Add test cases from relevant tickets
       - Clean up a bit of documentation
       - Desugar literal matches against floats into applications of the
         appropriate equality primitive instead of case analysis
       - Add a CoreLint to ensure we don't pattern match on floats in Core
      
      Test Plan: validate with included testcases
      
      Reviewers: goldfire, simonpj, austin
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1061
      
      GHC Trac Issues: #10215, #9238
      eb975d2e
  13. 23 Sep, 2015 1 commit
  14. 22 Sep, 2015 1 commit
  15. 21 Sep, 2015 3 commits
    • Edward Z. Yang's avatar
      Unify hsig and hs-boot; add preliminary "hs-boot" merging. · 06d46b1e
      Edward Z. Yang authored
      This patch drops the file level distinction between hs-boot and hsig;
      we figure out which one we are compiling based on whether or not there
      is a corresponding hs file lying around.
      
      To make the "import A" syntax continue to work for bare hs-boot
      files, we also introduce hs-boot merging, which takes an A.hi-boot
      and converts it to an A.hi when there is no A.hs file in scope.
      This will be generalized in Backpack to merge multiple A.hi files together;
      which means we can jettison the "load multiple interface files" functionality.
      
      This works automatically for --make, but for one-shot compilation
      we need a new mode: ghc --merge-requirements A will generate an A.hi/A.o
      from a local A.hi-boot file; Backpack will extend this mechanism further.
      
      Has Haddock submodule update to deal with change in msHsFilePath behavior.
      
          - This commit drops support for the hsig extension. Can
            we support it?  It's annoying because the finder code is
            written with the assumption that where there's an hs-boot
            file, there's always an hs file too.  To support hsig, you'd
            have to probe two locations.  Easier to just not support it.
      
          - #10333
      
       affects us, modifying an hs-boot still doesn't trigger
            recomp.
      
          - See compiler/main/Finder.hs: this diff is very skeevy, but
            it seems to work.
      
          - This code cunningly doesn't drop hs-boot files from the
            "drop hs-boot files" module graph, if they don't have a
            corresponding hs file.  I have no idea if this actually is useful.
      Signed-off-by: default avatarEdward Z. Yang <ezyang@cs.stanford.edu>
      
      Test Plan: validate
      
      Reviewers: simonpj, austin, bgamari, spinda
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1098
      06d46b1e
    • Edward Z. Yang's avatar
      3f13c20e
    • eir@cis.upenn.edu's avatar
      Allow TH quoting of assoc type defaults. · 1292c17e
      eir@cis.upenn.edu authored
      This fixes #10811.
      1292c17e
  16. 20 Sep, 2015 1 commit
  17. 17 Sep, 2015 1 commit
  18. 03 Sep, 2015 1 commit
  19. 18 Aug, 2015 2 commits
  20. 05 Aug, 2015 2 commits
    • Simon Peyton Jones's avatar
      Do not complain about SPECIALISE for INLINE · 617f6966
      Simon Peyton Jones authored
      Fixes Trac #10721.
      See Note [SPECIALISE on INLINE functions]
      617f6966
    • Simon Peyton Jones's avatar
      Allow proper errors/warnings in core2core passes · e2b57381
      Simon Peyton Jones authored
      This patch makes it possible for core-to-core passes to emit
      proper error messages and warnings.
      
        * New function CoreMonad.warnMsg
      
        * CoreMonad.warnMsg and errorMsg now print a proper warning/error
          message heading.
      
        * CoreMonad carries a SrcSpan, which is used in warning/error
          messages.  It is initialised to be the source file name, but
          a core-to-core pass could set it more specifically if it had
          better location information.
      
      There was a bit of plumbing needed to get the filename to the
      right place.
      e2b57381
  21. 02 Aug, 2015 1 commit
    • Alan Zimmerman's avatar
      Replace (SourceText,FastString) with StringLiteral data type · 15dd7007
      Alan Zimmerman authored
      Summary:
      Phab:D907 introduced SourceText for a number of data types, by replacing
      FastString with (SourceText,FastString). Since this has an Outputable
      instance, no warnings are generated when ppr is called on it, but
      unexpected output is generated. See Phab:D1096 for an example of this.
      
      Replace the (SourceText,FastString) tuples with a new data type,
      ```lang=hs
      data StringLiteral = StringLiteral SourceText FastString
      ```
      
      Update haddock submodule accordingly
      
      Test Plan: ./validate
      
      Reviewers: hvr, austin, rwbarton, trofi, bgamari
      
      Reviewed By: trofi, bgamari
      
      Subscribers: thomie, trofi, rwbarton, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D1101
      
      GHC Trac Issues: #10692
      15dd7007
  22. 30 Jul, 2015 2 commits
  23. 27 Jul, 2015 2 commits
    • Simon Peyton Jones's avatar
      Improve warnings for rules that might not fire · 2d88a531
      Simon Peyton Jones authored
      Two main things here
      
      * Previously we only warned about the "head" function of the rule,
        but actually the warning applies to any free variable on the LHS.
      
      * We now warn not only when one of these free vars can inline, but
        also if it has an active RULE (c.f. Trac #10528)
      
      See Note [Rules and inlining/other rules] in Desugar
      
      This actually shows up quite a few warnings in the libraries, notably
      in Control.Arrow, where it correctly points out that rules like
          "compose/arr"   forall f g .
                          (arr f) . (arr g) = arr (f . g)
      might never fire, because the rule for 'arr' (dictionary selection)
      might fire first.  I'm not really sure what to do here; there is some
      discussion in Trac #10595.
      
      A minor change is adding BasicTypes.pprRuleName to pretty-print RuleName.
      2d88a531
    • Adam Sandberg Eriksson's avatar
      Implementation of StrictData language extension · f842ad6c
      Adam Sandberg Eriksson authored
      This implements the `StrictData` language extension, which lets the
      programmer default to strict data fields in datatype declarations on a
      per-module basis.
      
      Specification and motivation can be found at
      https://ghc.haskell.org/trac/ghc/wiki/StrictPragma
      
      This includes a tricky parser change due to conflicts regarding `~` in
      the type level syntax: all ~'s are parsed as strictness annotations (see
      `strict_mark` in Parser.y) and then turned into equality constraints at
      the appropriate places using `RdrHsSyn.splitTilde`.
      
      Updates haddock submodule.
      
      Test Plan: Validate through Harbormaster.
      
      Reviewers: goldfire, austin, hvr, simonpj, tibbe, bgamari
      
      Reviewed By: simonpj, tibbe, bgamari
      
      Subscribers: lelf, simonpj, alanz, goldfire, thomie, bgamari, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D1033
      
      GHC Trac Issues: #8347
      f842ad6c
  24. 22 Jul, 2015 1 commit
  25. 21 Jul, 2015 1 commit
  26. 20 Jul, 2015 2 commits
    • Luite Stegeman's avatar
      Do not treat prim and javascript imports as C imports in TH and QQ · 4cd008b6
      Luite Stegeman authored
      Reviewers: austin, hvr, goldfire, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1070
      
      GHC Trac Issues: #10638
      4cd008b6
    • 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. 07 Jul, 2015 1 commit
  29. 26 Jun, 2015 1 commit
    • Simon Peyton Jones's avatar
      Treat out-of-scope variables as holes · fb7b6922
      Simon Peyton Jones authored
      This patch implements the idea in Trac #10569.
      
      * An out-of-scope variable is treated as a typed expression
        hole.
      
      * That is, we don't report it in the type checker, not the
        renamer, and we when we do report it, we give its type.
      
      * Moreover, we can defer the error to runtime with
        -fdefer-typed-holes
      
      In implementation terms:
      
      * The renamer turns an unbound variable into a HsUnboundVar
      
      * The type checker emits a Hole constraint for a
        HsUnboundVar, and turns it back into a HsVar
      
      It was a bit painful to implement because a whole raft of
      error messages change slightly.  But there was absolutely
      nothing hard in principle.
      
      Holes are reported with a bunch of possibly-useful context,
      notably the "relevant bindings".  I found that this was
      distracting clutter in the very common case of a mis-typed
      variable that is only accidentally not in scope, so I've
      arranged to print the context information only for true holes,
      that is ones starting with an underscore.
      
      Unbound data constructors use in patterns, like
        f (D x) = x
      are still reportd by the renamer, and abort compilation
      before type checking.
      fb7b6922