1. 15 Dec, 2016 1 commit
  2. 25 Nov, 2016 2 commits
    • Simon Peyton Jones's avatar
      Allow TyVars in TcTypes · 18d0bdd3
      Simon Peyton Jones authored
      Up to now we've had a rule that a TyVar can't apppear in a type
      seen by the type checker; they should all be TcTyVars.  But:
      
      a) With -XTypeInType it becomes much harder to exclude them;
         see Note [TcTyVars in the typechecker] in TcType.
      
      b) It's unnecessary to exculde them; instead we can just treat
         a TyVar just like vanillaSkolemTv.
      
      This is what was causing an ASSERT error in
      indexed-types/should_fail/T12041, reported in Trac #12826.
      
      That patch allows a TyVar in a TcType.  The most significant
      change is to make Var.tcTyVarDetails return vanillaSkolemTv.
      In fact it already did, but (a) it was not documented, and
      (b) we never exploited it.  Now we rely on it.
      18d0bdd3
    • Simon Peyton Jones's avatar
      Another major constraint-solver refactoring · 1eec1f21
      Simon Peyton Jones authored
      This patch takes further my refactoring of the constraint
      solver, which I've been doing over the last couple of months
      in consultation with Richard.
      
      It fixes a number of tricky bugs that made the constraint
      solver actually go into a loop, including
      
        Trac #12526
        Trac #12444
        Trac #12538
      
      The main changes are these
      
      * Flatten unification variables (fmvs/fuvs) appear on the LHS
        of a tvar/tyvar equality; thus
                 fmv ~ alpha
        and not
                 alpha ~ fmv
      
        See Note [Put flatten unification variables on the left]
        in TcUnify.  This is implemented by TcUnify.swapOverTyVars.
      
      * Don't reduce a "loopy" CFunEqCan where the fsk appears on
        the LHS:
            F t1 .. tn ~ fsk
        where 'fsk' is free in t1..tn.
        See Note [FunEq occurs-check principle] in TcInteract
      
        This neatly stops some infinite loops that people reported;
        and it allows us to delete some crufty code in reduce_top_fun_eq.
        And it appears to be no loss whatsoever.
      
        As well as fixing loops, ContextStack2 and T5837 both terminate
        when they didn't before.
      
      * Previously we generated "derived shadow" constraints from
        Wanteds, but we could (and sometimes did; Trac #xxxx) repeatedly
        generate a derived shadow from the same Wanted.
      
        A big change in this patch is to have two kinds of Wanteds:
           [WD] behaves like a pair of a Wanted and a Derived
           [W]  behaves like a Wanted only
        See CtFlavour and ShadowInfo in TcRnTypes, and the ctev_nosh
        field of a Wanted.
      
        This turned out to be a lot simpler.  A [WD] gets split into a
        [W] and a [D] in TcSMonad.maybeEmitShaodow.
      
        See TcSMonad Note [The improvement story and derived shadows]
      
      * Rather than have a separate inert_model in the InertCans, I've
        put the derived equalities back into inert_eqs.  We weren't
        gaining anything from a separate field.
      
      * Previously we had a mode for the constraint solver in which it
        would more aggressively solve Derived constraints; it was used
        for simplifying the context of a 'deriving' clause, or a 'default'
        delcaration, for example.
      
        But the complexity wasn't worth it; now I just make proper Wanted
        constraints.  See TcMType.cloneWC
      
      * Don't generate injectivity improvement for Givens; see
        Note [No FunEq improvement for Givens] in TcInteract
      
      * solveSimpleWanteds leaves the insolubles in-place rather than
        returning them.  Simpler.
      
      I also did lots of work on comments, including fixing Trac #12821.
      1eec1f21
  3. 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
  4. 21 Oct, 2016 3 commits
    • 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
    • Simon Peyton Jones's avatar
      A collection of type-inference refactorings. · 3f5673f3
      Simon Peyton Jones authored
      This patch does a raft of useful tidy-ups in the type checker.
      I've been meaning to do this for some time, and finally made
      time to do it en route to ICFP.
      
      1. Modify TcType.ExpType to make a distinct data type,
         InferResult for the Infer case, and consequential
         refactoring.
      
      2. Define a new function TcUnify.fillInferResult, to fill in
         an InferResult. It uses TcMType.promoteTcType to promote
         the type to the level of the InferResult.
         See TcMType Note [Promoting a type]
         This refactoring is in preparation for an improvement
         to typechecking pattern bindings, coming next.
      
         I flirted with an elaborate scheme to give better
         higher rank inference, but it was just too complicated.
         See TcMType Note [Promotion and higher rank types]
      
      3. Add to InferResult a new field ir_inst :: Bool to say
         whether or not the type used to fill in the
         InferResult should be deeply instantiated.  See
         TcUnify Note [Deep instantiation of InferResult].
      
      4. Add a TcLevel to SkolemTvs. This will be useful generally
      
          - it's a fast way to see if the type
            variable escapes when floating (not used yet)
      
          - it provides a good consistency check when updating a
            unification variable (TcMType.writeMetaTyVarRef, the
            level_check_ok check)
      
         I originally had another reason (related to the flirting
         in (2), but I left it in because it seems like a step in
         the right direction.
      
      5. Reduce and simplify the plethora of uExpType,
         tcSubType and related functions in TcUnify.  It was
         such an opaque mess and it's still not great, but it's
         better.
      
      6. Simplify the uo_expected field of TypeEqOrigin.  Richard
         had generatlised it to a ExpType, but it was almost always
         a Check type.  Now it's back to being a plain TcType which
         is much, much easier.
      
      7. Improve error messages by refraining from skolemisation when
         it's clear that there's an error: see
         TcUnify Note [Don't skolemise unnecessarily]
      
      8. Type.isPiTy and isForAllTy seem to be missing a coreView check,
         so I added it
      
      9. Kill off tcs_used_tcvs.  Its purpose is to track the
         givens used by wanted constraints.  For dictionaries etc
         we do that via the free vars of the /bindings/ in the
         implication constraint ic_binds.  But for coercions we
         just do update-in-place in the type, rather than
         generating a binding.  So we need something analogous to
         bindings, to track what coercions we have added.
      
         That was the purpose of tcs_used_tcvs.  But it only
         worked for a /single/ iteration, whereas we may have
         multiple iterations of solving an implication.  Look
         at (the old) 'setImplicationStatus'.  If the constraint
         is unsolved, it just drops the used_tvs on the floor.
         If it becomes solved next time round, we'll pick up
         coercions used in that round, but ignore ones used in
         the first round.
      
         There was an outright bug.  Result = (potentialy) bogus
         unused-constraint errors.  Constructing a case where this
         actually happens seems quite trick so I did not do so.
      
         Solution: expand EvBindsVar to include the (free vars of
         the) coercions, so that the coercions are tracked in
         essentially the same way as the bindings.
      
         This turned out to be much simpler.  Less code, more
         correct.
      
      10. Make the ic_binds field in an implication have type
            ic_binds :: EvBindsVar
          instead of (as previously)
             ic_binds :: Maybe EvBindsVar
          This is notably simpler, and faster to use -- less
          testing of the Maybe.  But in the occaional situation
          where we don't have anywhere to put the bindings, the
          belt-and-braces error check is lost.  So I put it back
          as an ASSERT in 'setImplicationStatus' (see the use of
          'termEvidenceAllowed')
      
      All these changes led to quite bit of error message wibbling
      3f5673f3
    • Gabor Greif's avatar
      Typos in comments · ff225b49
      Gabor Greif authored
      ff225b49
  5. 17 Oct, 2016 1 commit
  6. 30 Sep, 2016 1 commit
  7. 12 Sep, 2016 1 commit
    • Simon Peyton Jones's avatar
      Be less picky about reporing inaccessible code · 03541cba
      Simon Peyton Jones authored
      Triggered by the discussion on Trac #12466, this patch
      makes GHC less aggressive about reporting an error when
      there are insoluble Givens.
      
      Being so agressive was making some libraries fail to
      compile, and is arguably wrong in at least some cases.
      See the discussion on the ticket.
      
      Several test now pass when they failed before; see
      the files-modified list for this patch.
      03541cba
  8. 31 Aug, 2016 1 commit
  9. 17 Aug, 2016 1 commit
  10. 01 Aug, 2016 1 commit
  11. 28 Jun, 2016 1 commit
    • Simon Peyton Jones's avatar
      Don't omit any evidence bindings · af21e388
      Simon Peyton Jones authored
      This fixes Trac #12156, where we were omitting to make an
      evidence binding (because cec_suppress was on), but yet the
      program was compiled and run.
      
      The fix is easy, and involves deleting code :-).
      af21e388
  12. 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
  13. 23 Jun, 2016 1 commit
    • Simon Peyton Jones's avatar
      Give lookupGRE_Name a better API · 3e0af469
      Simon Peyton Jones authored
      lookupGRE_Name should return either zero or one GREs, never
      several. This is a consequence of INVARIANT 1 on GlobalRdrEnv.
      
      So it's better if it returns a Maybe; the panic on multiple results
      is put in one place, instead of being scattered or ignored.
      
      Just refactoring, no change in behaviour
      3e0af469
  14. 15 Jun, 2016 1 commit
    • 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
  15. 13 Jun, 2016 1 commit
    • Simon Peyton Jones's avatar
      Improve typechecking of let-bindings · 15b9bf4b
      Simon Peyton Jones authored
      This major commit was initially triggered by #11339, but it spiraled
      into a major review of the way in which type signatures for bindings
      are handled, especially partial type signatures.  On the way I fixed a
      number of other bugs, namely
         #12069
         #12033
         #11700
         #11339
         #11670
      
      The main change is that I completely reorganised the way in which type
      signatures in bindings are handled. The new story is in TcSigs
      Note [Overview of type signatures].  Some specific:
      
      * Changes in the data types for signatures in TcRnTypes:
        TcIdSigInfo and new TcIdSigInst
      
      * New module TcSigs deals with typechecking type signatures
        and pragmas. It contains code mostly moved from TcBinds,
        which is already too big
      
      * HsTypes: I swapped the nesting of HsWildCardBndrs
        and HsImplicitBndsrs, so that the wildcards are on the
        oustide not the insidde in a LHsSigWcType.  This is just
        a matter of convenient, nothing deep.
      
      There are a host of other changes as knock-on effects, and
      it all took FAR longer than I anticipated :-).  But it is
      a significant improvement, I think.
      
      Lots of error messages changed slightly, some just variants but
      some modest improvements.
      
      New tests
      
      * typecheck/should_compile
          * SigTyVars: a scoped-tyvar test
          * ExPat, ExPatFail: existential pattern bindings
          * T12069
          * T11700
          * T11339
      
      * partial-sigs/should_compile
          * T12033
          * T11339a
          * T11670
      
      One thing to check:
      
      * Small change to output from ghc-api/landmines.
        Need to check with Alan Zimmerman
      15b9bf4b
  16. 18 May, 2016 1 commit
    • niteria's avatar
      Kill varSetElems in tidyFreeTyCoVars · 6282bc31
      niteria authored
      I haven't observed this to have an effect on nondeterminism,
      but tidyOccName appears to modify the TidyOccEnv in a
      way dependent on the order of inputs.
      It's easy enough to change it to be deterministic to be on the
      safe side.
      
      Test Plan: ./validate
      
      Reviewers: simonmar, austin, bgamari, simonpj
      
      Reviewed By: simonpj
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2238
      
      GHC Trac Issues: #4012
      6282bc31
  17. 15 May, 2016 1 commit
    • Ömer Sinan Ağacan's avatar
      Fix a performance issue with -fprint-expanded-synonyms · e4834edf
      Ömer Sinan Ağacan authored
      The type synonym expander was doing redundant work by looking at same
      types again and again. This patch fixes the loop code when both of the
      types can be expanded, to do `O(min(n, m))` comparisons and `O(n + m)`
      expansions, where `n` is expansions of the first type and `m` is
      expansions of the second type.
      
      Reported by sjcjoosten in T10547.
      
      Test Plan:
      Added a regression test that was taking several minutes to type check
      before this patch.
      
      Reviewers: bgamari, simonpj, austin, ezyang
      
      Reviewed By: bgamari, simonpj, austin, ezyang
      
      Subscribers: simonpj, thomie
      
      Differential Revision: https://phabricator.haskell.org/D2198
      
      GHC Trac Issues: #10547
      e4834edf
  18. 12 May, 2016 1 commit
  19. 10 May, 2016 1 commit
    • niteria's avatar
      Kill unnecessary cmpType in lhs_cmp_type · 4ac0e815
      niteria authored
      This is the only call site of `lhs_cmp_type` and we only
      care about equality.
      `cmpType` is nondeterministic (because `TyCon`s are compared
      with Uniques in `cmpTc`), so if we don't have to use it, it's
      better not to.
      
      Test Plan: ./validate
      
      Reviewers: simonmar, goldfire, bgamari, austin, simonpj
      
      Reviewed By: simonpj
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2172
      
      GHC Trac Issues: #4012
      4ac0e815
  20. 28 Apr, 2016 2 commits
  21. 26 Apr, 2016 1 commit
    • niteria's avatar
      Kill varSetElems in TcErrors · 2dc5b92e
      niteria authored
      The uses of varSetElems in these places are unnecessary and while it
      doesn't intruduce non-determinism in the ABI the plan is to get
      rid of all varSetElems to get some compile time guarantees.
      
      Test Plan: ./validate
      
      Reviewers: austin, simonmar, bgamari, goldfire, simonpj
      
      Reviewed By: simonpj
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2141
      
      GHC Trac Issues: #4012
      2dc5b92e
  22. 19 Apr, 2016 1 commit
  23. 15 Apr, 2016 1 commit
    • niteria's avatar
      Kill some unnecessary varSetElems · 928d7473
      niteria authored
      When you do `varSetElems (tyCoVarsOfType x)` it's equivalent to
      `tyCoVarsOfTypeList x`.
      
      Why? If you look at the implementation:
      ```
      tyCoVarsOfTypeList ty = runFVList $ tyCoVarsOfTypeAcc ty
      tyCoVarsOfType ty = runFVSet $ tyCoVarsOfTypeAcc ty
      ```
      they use the same helper function. The helper function returns a
      deterministically ordered list and a set. The only difference
      between the two is which part of the result they take. It is redundant
      to take the set and then immediately convert it to a list.
      
      This helps with determinism and we eventually want to replace the uses
      of `varSetElems` with functions that don't leak the values of uniques.
      This change gets rid of some instances that are easy to kill.
      
      I chose not to annotate every place where I got rid of `varSetElems`
      with a comment about non-determinism, because once we get rid of
      `varSetElems` it will not be possible to do the wrong thing.
      
      Test Plan: ./validate
      
      Reviewers: goldfire, austin, simonmar, bgamari, simonpj
      
      Reviewed By: simonpj
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2115
      
      GHC Trac Issues: #4012
      928d7473
  24. 10 Apr, 2016 1 commit
    • Jason Eisenberg's avatar
      Fix suggestions for unbound variables (#11680) · 470d4d5b
      Jason Eisenberg authored
      When the typechecker generates the error message for an out-of-scope
      variable, it now uses the GlobalRdrEnv with respect to which the
      variable is unbound, not the GlobalRdrEnv which is available at the time
      the error is reported.  Doing so ensures we do not provide suggestions
      which themselves are out-of-scope (because they are bound in a later
      inter-splice group).
      
      Nonetheless, we do note in the error message if an unambiguous, exact
      match to the out-of-scope variable is found in a later inter-splice
      group, and we specify where that match is not in scope.
      
      Test Plan: ./validate
      
      Reviewers: goldfire, austin, bgamari
      
      Reviewed By: goldfire
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2000
      
      GHC Trac Issues: #11680
      470d4d5b
  25. 31 Mar, 2016 1 commit
  26. 24 Mar, 2016 1 commit
    • Rik Steenkamp's avatar
      Add `PatSynSigSkol` and modify `PatSynCtxt` · 997312b0
      Rik Steenkamp authored
      As the type of a pattern synonym cannot in general be represented by a
      value of type Type, we cannot use a value `SigSkol (PatSynCtxt n) (Check
      ty)` to represent the signature of a pattern synonym (this causes
      incorrect signatures to be printed in error messages). Therefore we now
      represent it by a value `PatSynSigSkol n` (instead of incorrect
      signatures we simply print no explicit signature).
      
      Furthermore, we rename `PatSynCtxt` to `PatSynBuilderCtxt`, and use
      `SigSkol (PatSynBuilderCtxt n) (Check ty)` to represent the type of a
      bidirectional pattern synonym when used in an expression context.
      Before, this type was represented by a value `SigSkol (PatSynCtxt n)
      (Check ty)`, which caused incorrect error messages.
      
      Also, in `mk_dict_err` of `typecheck\TcErrors.hs` we now distinguish
      between all enclosing implications and "useful" enclosing implications,
      for better error messages concerning pattern synonyms. See `Note [Useful
      implications]`.
      
      See the Phabricator page for examples.
      
      Reviewers: mpickering, goldfire, simonpj, austin, bgamari
      
      Reviewed By: bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1967
      
      GHC Trac Issues: #11667
      997312b0
  27. 16 Mar, 2016 1 commit
    • eir@cis.upenn.edu's avatar
      Clean up some pretty-printing in errors. · 5d98b8bf
      eir@cis.upenn.edu authored
      It turns out that there were some pretty egregious mistakes
      in the code that suggested -fprint-explicit-kinds, which are
      fixed. This commit also reorders a bunch of error messages,
      which I think is an improvement.
      
      This also adds the test case for #11471, which is what
      triggered the cleanup in TcErrors. Now that #11473 is done,
      there is nothing more outstanding for #11471.
      
      test case: dependent/should_fail/T11471
      5d98b8bf
  28. 15 Mar, 2016 1 commit
    • eir@cis.upenn.edu's avatar
      Fix #11407. · e9bf7bb5
      eir@cis.upenn.edu authored
      This removes the `defer_me` check that was in checkTauTvUpdate
      and uses only a type family check instead. The old defer_me check
      repeated work done by fast_check in occurCheckExpand.
      
      There is also some error message improvement, necessitated by
      the terrible error message that the test case produced, even when
      it didn't consume all of memory.
      
      test case: dependent/should_fail/T11407
      
      [skip ci]
      e9bf7bb5
  29. 27 Feb, 2016 2 commits
  30. 26 Feb, 2016 2 commits
    • Simon Peyton Jones's avatar
      Comments and white space only · 253ccdf0
      Simon Peyton Jones authored
      253ccdf0
    • Simon Peyton Jones's avatar
      Exclude TyVars from the constraint solver · 7496be5c
      Simon Peyton Jones authored
      There is a general invariant that the constraint solver doesn't see
      TyVars, only TcTyVars.  But when checking the generic-default
      signature of a class, we called checkValidType on the generic-default
      type, which had the class TyVar free. That in turn meant that it wasn't
      considered during flattening, which led to the error reported in
      Trac #11608.
      
      The fix is simple: call checkValidType on the /closed/ type. Easy.
      
      While I was at it, I added a bunch of ASSERTs about the TcTyVar
      invariant.
      7496be5c
  31. 25 Feb, 2016 2 commits
    • barrucadu's avatar
      Print which warning-flag controls an emitted warning · bb5afd3c
      barrucadu authored
      Both gcc and clang tell which warning flag a reported warning can be
      controlled with, this patch makes ghc do the same. More generally, this
      allows for annotated compiler output, where an optional annotation is
      displayed in brackets after the severity.
      
      This also adds a new flag `-f(no-)show-warning-groups` to control
      whether to show which warning-group (such as `-Wall` or `-Wcompat`)
      a warning belongs to. This flag is on by default.
      
      This implements #10752
      
      Reviewed By: quchen, bgamari, hvr
      
      Differential Revision: https://phabricator.haskell.org/D1943
      bb5afd3c
    • Rik Steenkamp's avatar
      Improve pattern synonym error messages (add `PatSynOrigin`) · 116528c8
      Rik Steenkamp authored
      Adds a new data constructor `PatSynOrigin Bool Name` to the `CtOrigin`
      data type. This allows for better error messages when the origin of a
      wanted constraint is a pattern synonym declaration.
      
      Fixes T10873.
      
      Reviewers: mpickering, simonpj, austin, thomie, bgamari
      
      Reviewed By: simonpj, thomie, bgamari
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1866
      
      GHC Trac Issues: #10873
      116528c8
  32. 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
  33. 17 Feb, 2016 1 commit