1. 29 Jul, 2017 1 commit
    • Richard Eisenberg's avatar
      Fix #14045 by omitting an unnecessary check · d1ef223c
      Richard Eisenberg authored
      Previously, we checked the number of patterns in a data instances
      for all data families whose kind did not end in a kind variable.
      But, of course, undersaturating instances can happen even without
      the kind ending in a kind variable. So I've omitted the arity check.
      Data families aren't as particular about their arity as type families
      are (because data families can be undersaturated). Still, this change
      degrades error messages when instances don't have the right arity;
      now, instead of reporting a simple mismatch in the number of patterns,
      GHC reports kind errors. The new errors are fully accurate, but perhaps
      not as easy to work with. Still, with the new flexibility of allowing
      data family instances with varying numbers of patterns, I don't see
      a better way.
      
      This commit also improves source fidelity in some error messages,
      requiring more changes than really are necessary. But without these
      changes, error messages around mismatched associated instance heads
      were poor.
      
      test cases: indexed-types/should_compile/T14045,
                  indexed-types/should_fail/T14045a
      d1ef223c
  2. 27 Jul, 2017 2 commits
    • Richard Eisenberg's avatar
      Fix #12369 by being more flexible with data insts · 42392383
      Richard Eisenberg authored
      Previously, a data family's kind had to end in `Type`,
      and data instances had to list all the type patterns for the
      family. However, both of these restrictions were unnecessary:
      
      - A data family's kind can usefully end in a kind variable `k`.
        See examples on #12369.
      
      - A data instance need not list all patterns, much like how a
        GADT-style data declaration need not list all type parameters,
        when a kind signature is in place. This is useful, for example,
        here:
      
          data family Sing (a :: k)
          data instance Sing :: Bool -> Type where ...
      
      This patch also improved a few error messages, as some error
      plumbing had to be moved around.
      
      See new Note [Arity of data families] in FamInstEnv for more
      info.
      
      test case: indexed-types/should_compile/T12369
      42392383
    • Richard Eisenberg's avatar
      Fix #13819 by refactoring TypeEqOrigin.uo_thing · c2417b87
      Richard Eisenberg authored
      The uo_thing field of TypeEqOrigin is used to track the
      "thing" (either term or type) that has the type (kind) stored
      in the TypeEqOrigin fields. Previously, this was sometimes a
      proper Core Type, which needed zonking and tidying. Now, it
      is only HsSyn: much simpler, and the error messages now use
      the user-written syntax.
      
      But this aspect of uo_thing didn't cause #13819; it was the
      sibling field uo_arity that did. uo_arity stored the number
      of arguments of uo_thing, useful when reporting something
      like "should have written 2 fewer arguments". We wouldn't want
      to say that if the thing didn't have two arguments. However,
      in practice, GHC was getting this wrong, and this message
      didn't seem all that helpful. Furthermore, the calculation
      of the number of arguments is what caused #13819 to fall over.
      This patch just removes uo_arity. In my opinion, the change
      to error messages is a nudge in the right direction.
      
      Test case: typecheck/should_fail/T13819
      c2417b87
  3. 26 Jul, 2017 2 commits
    • Gabor Greif's avatar
      Fix note references and some typos · 362339dd
      Gabor Greif authored
      362339dd
    • Simon Peyton Jones's avatar
      Fix binder visiblity for default methods · 75bf11c0
      Simon Peyton Jones authored
      Trac #13998 showed that default methods were getting bogus tyvar
      binder visiblity info; and that it matters in the code genreated
      by the default-method fill-in mechanism
      
      * The actual fix: in TcTyDecls.mkDefaultMethodType, make TyVarBinders
        with the right visibility info by getting TyConBinders from the
        class TyCon.  (Previously we made up visiblity info, but that
        caused #13998.)
      
      * Define TyCon.tyConTyVarBinders :: [TyConBinder] -> [TyVarBinder]
        which can build correct forall binders for
          a) default methods (Trac #13998)
          b) data constructors
        This was originally BuildTyCl.mkDataConUnivTyVarBinders
      
      * Move mkTyVarBinder, mkTyVarBinders from Type to Var
      75bf11c0
  4. 19 Jul, 2017 1 commit
    • Ryan Scott's avatar
      Fix #13983 by creating a TyConFlavour type, and using it · 6e3c901d
      Ryan Scott authored
      An error message was referring to a type synonym as a datatype.
      Annoyingly, learning that the TyCon over which the error message is
      operating is actually a type synonym was previously impossible, since
      that code only had access to a TcTyCon, which doesn't retain any
      information about what sort of TyCon it is.
      
      To rectify this, I created a new TyConFlavour datatype, intended to
      capture roughly what sort of TyCon we're dealing with. I then performing
      the necessary plumbing to ensure all TcTyCons have a TyConFlavour, and
      propagated this information through to the relevant error message.
      
      Test Plan: ./validate
      
      Reviewers: goldfire, austin, bgamari, simonpj
      
      Reviewed By: simonpj
      
      Subscribers: simonpj, rwbarton, thomie
      
      GHC Trac Issues: #13983
      
      Differential Revision: https://phabricator.haskell.org/D3747
      6e3c901d
  5. 11 Jul, 2017 1 commit
  6. 03 Jul, 2017 1 commit
    • Ryan Scott's avatar
      Fix #13311 by using tcSplitNestedSigmaTys in the right place · c3a78623
      Ryan Scott authored
      Previously, we we only using `tcSplitSigmaTy` when determining if a
      function had been applied to too few arguments, so it wouldn't work for
      functions with nested `forall`s. Thankfully, this is easily fixed with a
      dash of `tcSplitNestedSigmaTys`.
      
      Test Plan: make test TEST=T13311
      
      Reviewers: austin, bgamari, simonpj
      
      Reviewed By: bgamari
      
      Subscribers: goldfire, simonpj, rwbarton, thomie
      
      GHC Trac Issues: #13311
      
      Differential Revision: https://phabricator.haskell.org/D3678
      c3a78623
  7. 28 Jun, 2017 1 commit
    • Simon Peyton Jones's avatar
      Do zonking in tcLHsKindSig · c80920d2
      Simon Peyton Jones authored
      Trac #13879 showed that there was a missing zonk in tcLHsKind.
      
      I also renamed it to tcLHsKindSig, for consistency with type signatures
      There's a commment to explain why the zonk is needed.
      c80920d2
  8. 05 Jun, 2017 1 commit
    • Alan Zimmerman's avatar
      Udate hsSyn AST to use Trees that Grow · 8e6ec0fa
      Alan Zimmerman authored
      Summary:
      See https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow
      
      This commit prepares the ground for a full extensible AST, by replacing the type
      parameter for the hsSyn data types with a set of indices into type families,
      
          data GhcPs -- ^ Index for GHC parser output
          data GhcRn -- ^ Index for GHC renamer output
          data GhcTc -- ^ Index for GHC typechecker output
      
      These are now used instead of `RdrName`, `Name` and `Id`/`TcId`/`Var`
      
      Where the original name type is required in a polymorphic context, this is
      accessible via the IdP type family, defined as
      
          type family IdP p
          type instance IdP GhcPs = RdrName
          type instance IdP GhcRn = Name
          type instance IdP GhcTc = Id
      
      These types are declared in the new 'hsSyn/HsExtension.hs' module.
      
      To gain a better understanding of the extension mechanism, it has been applied
      to `HsLit` only, also replacing the `SourceText` fields in them with extension
      types.
      
      To preserve extension generality, a type class is introduced to capture the
      `SourceText` interface, which must be honoured by all of the extension points
      which originally had a `SourceText`.  The class is defined as
      
          class HasSourceText a where
            -- Provide setters to mimic existing constructors
            noSourceText  :: a
            sourceText    :: String -> a
      
            setSourceText :: SourceText -> a
            getSourceText :: a -> SourceText
      
      And the constraint is captured in `SourceTextX`, which is a constraint type
      listing all the extension points that make use of the class.
      
      Updating Haddock submodule to match.
      
      Test Plan: ./validate
      
      Reviewers: simonpj, shayan-najd, goldfire, austin, bgamari
      
      Subscribers: rwbarton, thomie, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D3609
      8e6ec0fa
  9. 02 Jun, 2017 1 commit
    • Ryan Scott's avatar
      Use lengthIs and friends in more places · a786b136
      Ryan Scott authored
      While investigating #12545, I discovered several places in the code
      that performed length-checks like so:
      
      ```
      length ts == 4
      ```
      
      This is not ideal, since the length of `ts` could be much longer than 4,
      and we'd be doing way more work than necessary! There are already a slew
      of helper functions in `Util` such as `lengthIs` that are designed to do
      this efficiently, so I found every place where they ought to be used and
      did just that. I also defined a couple more utility functions for list
      length that were common patterns (e.g., `ltLength`).
      
      Test Plan: ./validate
      
      Reviewers: austin, hvr, goldfire, bgamari, simonmar
      
      Reviewed By: bgamari, simonmar
      
      Subscribers: goldfire, rwbarton, thomie
      
      Differential Revision: https://phabricator.haskell.org/D3622
      a786b136
  10. 26 May, 2017 1 commit
  11. 19 May, 2017 1 commit
  12. 13 Apr, 2017 1 commit
    • Simon Peyton Jones's avatar
      Remove dead quantifyTyVars · fbb27d77
      Simon Peyton Jones authored
      This patch
      
      * removes a function TcMType.quantifyTyVars
        that was never called
      
      * renames quantifyZonkedTyVars to quantifyTyVars
      
      Plus a few comments.  No functional change at all
      fbb27d77
  13. 12 Apr, 2017 1 commit
  14. 14 Mar, 2017 1 commit
    • Richard Eisenberg's avatar
      Fix #13337. · e0c433c8
      Richard Eisenberg authored
      The big change is the introduction of solveSomeEqualities. This
      is just like solveEqualities, but it doesn't fail if there are unsolved
      equalities when it's all done. Anything unsolved is re-emitted. This
      is appropriate if we are not kind-generalizing, so this new form
      is used when decideKindGeneralizationPlan says not to.
      
      We initially thought that any use of solveEqualities would be tied
      to kind generalization, but this isn't true. For example, we need
      to solveEqualities a bunch in the "tc" pass in TcTyClsDecls (which
      is really desugaring). These equalities are all surely going to be
      soluble (if they weren't the "kc" pass would fail), but we still
      need to solve them again. Perhaps if the "kc" pass produced type-
      checked output that is then desugared, solveEqualities really would
      be tied only to kind generalization.
      
      Updates haddock submodule.
      
      Test Plan: ./validate, typecheck/should_compile/T13337
      
      Reviewers: simonpj, bgamari, austin
      
      Reviewed By: simonpj
      
      Subscribers: RyanGlScott, rwbarton, thomie
      
      Differential Revision: https://phabricator.haskell.org/D3315
      e0c433c8
  15. 02 Mar, 2017 1 commit
    • Edward Z. Yang's avatar
      Properly represent abstract classes in Class and IfaceDecl · fb5cd9d6
      Edward Z. Yang authored
      Summary:
      Previously, abstract classes looked very much like normal
      classes, except that they happened to have no methods,
      superclasses or ATs, and they came from boot files.  This
      patch gives abstract classes a proper representation in
      Class and IfaceDecl, by moving the things which are never
      defined for abstract classes into ClassBody/IfaceClassBody.
      
      Because Class is abstract, this change had ~no disruption
      to any of the code in GHC; if you ask about the methods of
      an abstract class, we'll just give you an empty list.
      
      This also fixes a bug where abstract type classes were incorrectly
      treated as representationally injective (they're not!)
      
      Fixes #13347, and a TODO in the code.
      Signed-off-by: default avatarEdward Z. Yang <ezyang@cs.stanford.edu>
      
      Test Plan: validate
      
      Reviewers: simonpj, bgamari, austin
      
      Subscribers: goldfire, thomie
      
      Differential Revision: https://phabricator.haskell.org/D3236
      fb5cd9d6
  16. 27 Feb, 2017 2 commits
    • Edward Z. Yang's avatar
      Subtyping for roles in signatures. · 923d7ca2
      Edward Z. Yang authored
      Summary:
      This commit implements the plan in #13140:
      
      * Today, roles in signature files default to representational. Let's change the
        default to nominal, as this is the most flexible implementation side. If a
        client of the signature needs to coerce with a type, the signature can be
        adjusted to have more stringent requirements.
      
      * If a parameter is declared as nominal in a signature, it can be implemented
        by a data type which is actually representational.
      
      * When merging abstract data declarations, we take the smallest role for every
        parameter. The roles are considered fix once we specify the structure of an
        ADT.
      
      * Critically, abstract types are NOT injective, so we aren't allowed to
        make inferences like "if T a ~R T b, then a ~N b" based on the nominal
        role of a parameter in an abstract type (this would be unsound if the
        parameter ended up being phantom.)  This restriction is similar to the
        restriction we have on newtypes.
      Signed-off-by: default avatarEdward Z. Yang <ezyang@cs.stanford.edu>
      
      Test Plan: validate
      
      Reviewers: simonpj, bgamari, austin, goldfire
      
      Subscribers: goldfire, thomie
      
      Differential Revision: https://phabricator.haskell.org/D3123
      923d7ca2
    • Edward Z. Yang's avatar
      Treat all TyCon with hole names as skolem abstract. · 9603de6a
      Edward Z. Yang authored
      Summary:
      Fixes #13335.
      Signed-off-by: default avatarEdward Z. Yang <ezyang@cs.stanford.edu>
      
      Test Plan: validate
      
      Reviewers: goldfire, austin, simonpj, bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D3211
      9603de6a
  17. 21 Feb, 2017 2 commits
    • Simon Peyton Jones's avatar
      A bit more tc-tracing in TcTyClsDecls · e3e218e2
      Simon Peyton Jones authored
      e3e218e2
    • Simon Peyton Jones's avatar
      Remove panics for TcTyCon · 0c9d9dec
      Simon Peyton Jones authored
      Previously TcTyCons were used only for knot-tying, but now they
      are also used after an error, to add a benign TyCon to the envt
      so we can carry on; see TyCon.makeRecoveryTyCon.  But since it
      is used in this way, subsequent declarations may see a TcTyCon
      (e.g. during injectivity checks) and should not have a heart attack
      as a result.
      
      See Note [TcTyCon] in TyCon.
      
      This fixes Trac #13271
      0c9d9dec
  18. 20 Feb, 2017 1 commit
  19. 30 Jan, 2017 1 commit
    • Ryan Scott's avatar
      Check that a default type signature aligns with the non-default signature · 7363d538
      Ryan Scott authored
      Before, GHC was extremely permissive about the form a default type
      signature could take on in a class declaration. Notably, it would accept
      garbage like this:
      
        class Monad m => MonadSupply m where
          fresh :: m Integer
          default fresh :: MonadTrans t => t m Integer
          fresh = lift fresh
      
      And then give an extremely confusing error message when you actually
      tried to declare an empty instance of MonadSupply. We now do extra
      validity checking of default type signatures to ensure that they align
      with their non-default type signature counterparts. That is, a default
      type signature is allowed to differ from the non-default one only in its
      context - they must otherwise be alpha-equivalent.
      
      Fixes #12918.
      
      Test Plan: ./validate
      
      Reviewers: goldfire, simonpj, austin, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: mpickering, dfeuer, thomie
      
      Differential Revision: https://phabricator.haskell.org/D2983
      
      GHC Trac Issues: #12918
      7363d538
  20. 26 Jan, 2017 1 commit
  21. 19 Jan, 2017 1 commit
    • Richard Eisenberg's avatar
      Update levity polymorphism · e7985ed2
      Richard Eisenberg authored
      This commit implements the proposal in
      https://github.com/ghc-proposals/ghc-proposals/pull/29 and
      https://github.com/ghc-proposals/ghc-proposals/pull/35.
      
      Here are some of the pieces of that proposal:
      
      * Some of RuntimeRep's constructors have been shortened.
      
      * TupleRep and SumRep are now parameterized over a list of RuntimeReps.
      * This
      means that two types with the same kind surely have the same
      representation.
      Previously, all unboxed tuples had the same kind, and thus the fact
      above was
      false.
      
      * RepType.typePrimRep and friends now return a *list* of PrimReps. These
      functions can now work successfully on unboxed tuples. This change is
      necessary because we allow abstraction over unboxed tuple types and so
      cannot
      always handle unboxed tuples specially as we did before.
      
      * We sometimes have to create an Id from a PrimRep. I thus split PtrRep
      * into
      LiftedRep and UnliftedRep, so that the created Ids have the right
      strictness.
      
      * The RepType.RepType type was removed, as it didn't seem to help with
      * much.
      
      * The RepType.repType function is also removed, in favor of typePrimRep.
      
      * I have waffled a good deal on whether or not to keep VoidRep in
      TyCon.PrimRep. In the end, I decided to keep it there. PrimRep is *not*
      represented in RuntimeRep, and typePrimRep will never return a list
      including
      VoidRep. But it's handy to have in, e.g., ByteCodeGen and friends. I can
      imagine another design choice where we have a PrimRepV type that is
      PrimRep
      with an extra constructor. That seemed to be a heavier design, though,
      and I'm
      not sure what the benefit would be.
      
      * The last, unused vestiges of # (unliftedTypeKind) have been removed.
      
      * There were several pretty-printing bugs that this change exposed;
      * these are fixed.
      
      * We previously checked for levity polymorphism in the types of binders.
      * But we
      also must exclude levity polymorphism in function arguments. This is
      hard to check
      for, requiring a good deal of care in the desugarer. See Note [Levity
      polymorphism
      checking] in DsMonad.
      
      * In order to efficiently check for levity polymorphism in functions, it
      * was necessary
      to add a new bit of IdInfo. See Note [Levity info] in IdInfo.
      
      * It is now safe for unlifted types to be unsaturated in Core. Core Lint
      * is updated
      accordingly.
      
      * We can only know strictness after zonking, so several checks around
      * strictness
      in the type-checker (checkStrictBinds, the check for unlifted variables
      under a ~
      pattern) have been moved to the desugarer.
      
      * Along the way, I improved the treatment of unlifted vs. banged
      * bindings. See
      Note [Strict binds checks] in DsBinds and #13075.
      
      * Now that we print type-checked source, we must be careful to print
      * ConLikes correctly.
      This is facilitated by a new HsConLikeOut constructor to HsExpr.
      Particularly troublesome
      are unlifted pattern synonyms that get an extra void# argument.
      
      * Includes a submodule update for haddock, getting rid of #.
      
      * New testcases:
        typecheck/should_fail/StrictBinds
        typecheck/should_fail/T12973
        typecheck/should_run/StrictPats
        typecheck/should_run/T12809
        typecheck/should_fail/T13105
        patsyn/should_fail/UnliftedPSBind
        typecheck/should_fail/LevPolyBounded
        typecheck/should_compile/T12987
        typecheck/should_compile/T11736
      
      * Fixed tickets:
        #12809
        #12973
        #11736
        #13075
        #12987
      
      * This also adds a test case for #13105. This test case is
      * "compile_fail" and
      succeeds, because I want the testsuite to monitor the error message.
      When #13105 is fixed, the test case will compile cleanly.
      e7985ed2
  22. 18 Dec, 2016 1 commit
  23. 17 Dec, 2016 1 commit
    • eir@cis.upenn.edu's avatar
      Reshuffle levity polymorphism checks. · 8906e7b7
      eir@cis.upenn.edu authored
      Previously, GHC checked for bad levity polymorphism to the left of all
      arrows in data constructors. This was wrong, as reported in #12911
      (where an example is also shown). The solution is to check each
      individual argument for bad levity polymorphism.  Thus the check has
      been moved from TcValidity to TcTyClsDecls.
      
      A similar situation exists with pattern synonyms, also fixed here.
      
      This patch also nabs #12819 while I was in town.
      
      Test cases: typecheck/should_compile/T12911, patsyn/should_fail/T12819
      
      Test Plan: ./validate
      
      Reviewers: simonpj, austin, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2783
      
      GHC Trac Issues: #12819, #12911
      8906e7b7
  24. 07 Dec, 2016 1 commit
    • Alan Zimmerman's avatar
      Add HsSyn prettyprinter tests · 499e4382
      Alan Zimmerman authored
      Summary:
      Add prettyprinter tests, which take a file, parse it, pretty print it,
      re-parse the pretty printed version and then compare the original and
      new ASTs (ignoring locations)
      
      Updates haddock submodule to match the AST changes.
      
      There are three issues outstanding
      
      1. Extra parens around a context are not reproduced. This will require an
         AST change and will be done in a separate patch.
      
      2. Currently if an `HsTickPragma` is found, this is not pretty-printed,
         to prevent noise in the output.
      
         I am not sure what the desired behaviour in this case is, so have left
         it as before. Test Ppr047 is marked as expected fail for this.
      
      3. Apart from in a context, the ParsedSource AST keeps all the parens from
         the original source.  Something is happening in the renamer to remove the
         parens around visible type application, causing T12530 to fail, as the
         dumped splice decl is after the renamer.
      
         This needs to be fixed by keeping the parens, but I do not know where they
         are being removed.  I have amended the test to pass, by removing the parens
         in the expected output.
      
      Test Plan: ./validate
      
      Reviewers: goldfire, mpickering, simonpj, bgamari, austin
      
      Reviewed By: simonpj, bgamari
      
      Subscribers: simonpj, goldfire, thomie, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D2752
      
      GHC Trac Issues: #3384
      499e4382
  25. 25 Nov, 2016 1 commit
    • Simon Peyton Jones's avatar
      Use TyVars in PatSyns · 12eff239
      Simon Peyton Jones authored
      I found that some TcTyVars were lurking in a PatSyn, because
      tc_patsyn_finish was using the TcType -> TcType zonker rather
      than the TcType -> Type zonker.  Eeek.
      
      I fixing this I also tided up function naming a bit (still not
      terrific), and removed the unused TcTyBinder type entirely.
      12eff239
  26. 17 Nov, 2016 1 commit
    • Edward Z. Yang's avatar
      Test for type synonym loops on TyCon. · 31398fbc
      Edward Z. Yang authored
      Summary:
      Previously, we tested for type synonym loops by doing
      a syntactic test on the literal type synonym declarations.
      However, in some cases, loops could go through hs-boot
      files, leading to an infinite loop (#12042); a similar
      situation can occur when signature merging.
      
      This commit replaces the syntactic test with a test on
      TyCon, simply by walking down all type synonyms until
      we bottom out, or find we've looped back.  It's a lot
      simpler.
      Signed-off-by: default avatarEdward Z. Yang <ezyang@cs.stanford.edu>
      
      Test Plan: validate
      
      Reviewers: simonpj, austin, bgamari
      
      Subscribers: goldfire, thomie
      
      Differential Revision: https://phabricator.haskell.org/D2656
      
      GHC Trac Issues: #12042
      31398fbc
  27. 13 Nov, 2016 1 commit
    • Ben Gamari's avatar
      Kill Type pretty-printer · 6c0f10fa
      Ben Gamari authored
      Here we consolidate the pretty-printing logic for types in IfaceType. We
      need IfaceType regardless and the printer for Type can be implemented in
      terms of that for IfaceType. See #11660.
      
      Note that this is very much a work-in-progress. Namely I still have yet
      to ponder how to ease the hs-boot file situation, still need to rip out
      more dead code, need to move some of the special cases for, e.g., `*` to
      the IfaceType printer, and need to get it to validate. That being said,
      it comes close to validating as-is.
      
      Test Plan: Validate
      
      Reviewers: goldfire, austin
      
      Subscribers: goldfire, thomie, simonpj
      
      Differential Revision: https://phabricator.haskell.org/D2528
      
      GHC Trac Issues: #11660
      6c0f10fa
  28. 02 Nov, 2016 2 commits
    • Simon Peyton Jones's avatar
      Simplify the API for TcHsType.kcHsTyVarBndrs · 7a509660
      Simon Peyton Jones authored
      Pass in a Bool rather than return a funcion!
      
      No change in behaviour.
      7a509660
    • Simon Peyton Jones's avatar
      Get rid of TcTyVars more assiduously · 99689492
      Simon Peyton Jones authored
      * I found a bug in 'generalize' in TcTyClsDecls.kcTyClGroup, where
        the kind variables weren't being turned into proper TyVars, so
        we got (skolem) TcTyVars in TyCons, which shouldn't happen.  Fix
        was easy.
      
      * Similarly TcHsType.kindGeneralizeType wasn't turning the forall'd
        TcTyVars into TyVars.  To achieve this I defined TcHsTyn.zonkSigType.
      
      * All this allowed me to remove awkward and ill-explained bit of
        footwork on DFunIds in Inst.newClsInst
      
      This is just refactoring, but it does make the printout from
      -ddump-deriv make a bit more sense by not grautuitiously cloning
      type variables.  In the display I was seeing
      
         instance C [a_df4] where
            f x = ...a_dx5...
      
      where actually the d_df4 and a_dx5 were the same.
      99689492
  29. 31 Oct, 2016 1 commit
  30. 27 Oct, 2016 1 commit
  31. 21 Oct, 2016 1 commit
    • Simon Peyton Jones's avatar
      Refactor occurrence-check logic · 9417e579
      Simon Peyton Jones authored
      This patch does two related things
      
      * Combines the occurrence-check logic in the on-the-fly unifier with
        that in the constraint solver.  They are both doing the same job,
        after all.  The resulting code is now in TcUnify:
           metaTyVarUpdateOK
           occCheckExpand
           occCheckForErrors (called in TcErrors)
      
      * In doing this I disovered checking for family-free-ness and foralls
        can be unnecessarily inefficient, because it expands type synonyms.
        It's easy just to cache this info in the type syononym TyCon, which
        I am now doing.
      9417e579
  32. 20 Oct, 2016 1 commit
    • Edward Z. Yang's avatar
      New story for abstract data types in hsig files. · 518f2895
      Edward Z. Yang authored
      Summary:
      In the old implementation of hsig files, we directly
      reused the implementation of abstract data types from
      hs-boot files.  However, this was WRONG.  Consider the
      following program (an abridged version of bkpfail24):
      
          {-# LANGUAGE GADTs #-}
          unit p where
              signature H1 where
                  data T
              signature H2 where
                  data T
              module M where
                  import qualified H1
                  import qualified H2
      
                  f :: H1.T ~ H2.T => a -> b
                  f x = x
      
      Prior to this patch, M was accepted, because the type
      inference engine concluded that H1.T ~ H2.T does not
      hold (indeed, *presently*, it does not).  However, if
      we subsequently instantiate p with the same module for
      H1 and H2, H1.T ~ H2.T does hold!  Unsound.
      
      The key is that abstract types from signatures need to
      be treated like *skolem variables*, since you can interpret
      a Backpack unit as a record which is universally quantified
      over all of its abstract types, as such (with some fake
      syntax for structural records):
      
          p :: forall t1 t2. { f :: t1 ~ t2 => a -> b }
          p = { f = \x -> x } -- ill-typed
      
      Clearly t1 ~ t2 is not solvable inside p, and also clearly
      it could be true at some point in the future, so we better
      not treat the lambda expression after f as inaccessible.
      
      The fix seems to be simple: do NOT eagerly fail when trying
      to simplify the given constraints.  Instead, treat H1.T ~ H2.T
      as an irreducible constraint (rather than an insoluble
      one); this causes GHC to treat f as accessible--now we will
      typecheck the rest of the function (and correctly fail).
      Per the OutsideIn(X) paper, it's always sound to fail less
      when simplifying givens.
      
      We do NOT apply this fix to hs-boot files, where abstract
      data is also guaranteed to be nominally distinct (since
      it can't be implemented via a reexport or a type synonym.)
      This is a somewhat unnatural state of affairs (there's
      no way to really interpret this in Haskell land) but
      no reason to change behavior.
      
      I deleted "representationally distinct abstract data",
      which is never used anywhere in GHC.
      
      In the process of constructing this fix, I also realized
      our implementation of type synonym matching against abstract
      data was not sufficiently restrictive.  In order for
      a type synonym T to be well-formed type, it must be a
      nullary synonym (i.e., type T :: * -> *, not type T a = ...).
      Furthermore, since we use abstract data when defining
      instances, they must not have any type family applications.
      
      More details in #12680.  This probably deserves some sort
      of short paper report.
      Signed-off-by: default avatarEdward Z. Yang <ezyang@cs.stanford.edu>
      
      Test Plan: validate
      
      Reviewers: goldfire, simonpj, austin, bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2594
      518f2895
  33. 19 Oct, 2016 1 commit
    • Simon Peyton Jones's avatar
      Test for newtype with unboxed argument · 1f09c16c
      Simon Peyton Jones authored
      Newtypes cannot (currently) have an unboxed argument type.
      But Trac #12729 showed that this was only being checked for
      newtypes in H98 syntax; in GADT snytax they were let through.
      
      This patch moves the test to checkValidDataCon, where it properly
      belongs.
      1f09c16c
  34. 10 Oct, 2016 1 commit
    • Simon Peyton Jones's avatar
      Move zonking out of tcFamTyPats · 76a5477b
      Simon Peyton Jones authored
      In tcFamTyPats we were zonking from the TcType world to the
      Type world, ready to build the results into a CoAxiom (which
      should have no TcType stuff.  But the 'thing_inside' for
      tcFamTyPats also must be zonked, and that zonking must have
      the ZonkEnv from the binders zonked tcFamTyPats.
      
      Ugh.  This caused an assertion failure (with DEBUG on) in
      RaeBlobPost and TypeLevelVec, both in tests/dependent, as
      shown in Trac #12682.  Why it hasn't shown up before now
      is obscure to me.
      
      So I moved the zonking stuff out of tcFamTyPats to its
      three call sites, where we can do it all together. Very
      slightly longer, but much more robust.
      76a5477b
  35. 05 Jul, 2016 1 commit
    • Simon Peyton Jones's avatar
      Check generic-default method for ambiguity · 85aa6ef0
      Simon Peyton Jones authored
      Fixes Trac #7497 and #12151.   In some earlier upheaval I introduced
      a bug in the ambiguity check for genreric-default method.
      
      This patch fixes it.  But in fixing it I realised that the
      sourc-location of any such error message was bogus, so I fixed
      that too, which involved a slightly wider change; see the
      comments with TcMethInfo.
      85aa6ef0