1. 24 Nov, 2015 1 commit
    • elaforge's avatar
      Rearrange error msgs and add section markers (Trac #11014). · c05fddde
      elaforge authored
      This puts the "Relevant bindings" section at the end.
      
      It uses a TcErrors.Report Monoid to divide messages by importance and
      then mappends them together.  This is not the most efficient way since
      there are various intermediate Reports and list appends, but it probably
      doesn't matter since error messages shouldn't get that large, and are
      usually prepended.  In practice, everything is `important` except
      `relevantBindings`, which is `supplementary`.
      
      ErrMsg's errMsgShortDoc and errMsgExtraInfo were extracted into ErrDoc,
      which has important, context, and suppelementary fields.  Each of those
      three sections is marked with a bullet character, '•' on unicode
      terminals and '*' on ascii terminals.  Since this breaks tons of tests,
      I also modified testlib.normalise_errmsg to strip out '•'s.
      
      --- Additional notes:
      
      To avoid prepending * to an empty doc, I needed to filter empty docs.
      This seemed less error-prone than trying to modify everyone who produces
      SDoc to instead produce Maybe SDoc.  So I added `Outputable.isEmpty`.
      Unfortunately it needs a DynFlags, which is kind of bogus, but otherwise
      I think I'd need another Empty case for SDoc, and then it couldn't be a
      newtype any more.
      
      ErrMsg's errMsgShortString is only used by the Show instance, which is
      in turn only used by Show HscTypes.SourceError, which is in turn only
      needed for the Exception instance.  So it's probably possible to get rid
      of errMsgShortString, but that would a be an unrelated cleanup.
      
      Fixes #11014.
      
      Test Plan: see above
      
      Reviewers: austin, simonpj, thomie, bgamari
      
      Reviewed By: thomie, bgamari
      
      Subscribers: simonpj, nomeata, thomie
      
      Differential Revision: https://phabricator.haskell.org/D1427
      
      GHC Trac Issues: #11014
      c05fddde
  2. 06 Jan, 2015 1 commit
    • Simon Peyton Jones's avatar
      Modify a couple of error messages slightly · 00e1fc1b
      Simon Peyton Jones authored
      In particular
        In the type signature for:
           f :: Int -> Int
      I added the colon
      
      Also reword the "maybe you haven't applied a function to enough arguments?"
      suggestion to make grammatical sense.
      
      These tiny changes affect a lot of error messages.
      00e1fc1b
  3. 25 Feb, 2014 1 commit
  4. 01 Oct, 2013 1 commit
    • unknown's avatar
      Error message wibbles, · 0ad7cdb3
      unknown authored
      following
        a) suppressing kind foralls and arguments
        b) better fundep error messages
      0ad7cdb3
  5. 10 Sep, 2013 1 commit
    • Simon Peyton Jones's avatar
      Error message wibbles · 9ca4a73d
      Simon Peyton Jones authored
      Almost all are re-orderings of relevant-binding output
      
             Relevant bindings include
        +      m :: Map (a, b) elt (bound at T3169.hs:12:17)
        +      b :: b (bound at T3169.hs:12:13)
               lookup :: (a, b) -> Map (a, b) elt -> Maybe elt
                 (bound at T3169.hs:12:3)
        -      b :: b (bound at T3169.hs:12:13)
        -      m :: Map (a, b) elt (bound at T3169.hs:12:17)
      9ca4a73d
  6. 21 Jun, 2013 1 commit
  7. 24 Feb, 2013 1 commit
  8. 22 Dec, 2012 1 commit
    • eir@cis.upenn.edu's avatar
      Implement overlapping type family instances. · 7a42cf66
      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.
      7a42cf66