1. 19 Apr, 2019 1 commit
    • Alec Theriault's avatar
      TH: make `Lift` and `TExp` levity-polymorphic · 57cf1133
      Alec Theriault authored
      Besides the obvious benefits of being able to manipulate `TExp`'s of
      unboxed types, this also simplified `-XDeriveLift` all while making
      it more capable.
      
        * `ghc-prim` is explicitly depended upon by `template-haskell`
      
        * The following TH things are parametrized over `RuntimeRep`:
      
            - `TExp(..)`
            - `unTypeQ`
            - `unsafeTExpCoerce`
            - `Lift(..)`
      
        * The following instances have been added to `Lift`:
      
            - `Int#`, `Word#`, `Float#`, `Double#`, `Char#`, `Addr#`
            - unboxed tuples of lifted types up to arity 7
            - unboxed sums of lifted types up to arity 7
      
          Ideally we would have levity-polymorphic _instances_ of unboxed
          tuples and sums.
      
        * The code generated by `-XDeriveLift` uses expression quotes
          instead of generating large amounts of TH code and having
          special hard-coded cases for some unboxed types.
      57cf1133
  2. 15 Mar, 2019 1 commit
  3. 01 Mar, 2019 1 commit
    • Ryan Scott's avatar
      Visible dependent quantification · c26d299d
      Ryan Scott authored
      This implements GHC proposal 35
      (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0035-forall-arrow.rst)
      by adding the ability to write kinds with
      visible dependent quantification (VDQ).
      
      Most of the work for supporting VDQ was actually done _before_ this
      patch. That is, GHC has been able to reason about kinds with VDQ for
      some time, but it lacked the ability to let programmers directly
      write these kinds in the source syntax. This patch is primarly about
      exposing this ability, by:
      
      * Changing `HsForAllTy` to add an additional field of type
        `ForallVisFlag` to distinguish between invisible `forall`s (i.e,
        with dots) and visible `forall`s (i.e., with arrows)
      * Changing `Parser.y` accordingly
      
      The rest of the patch mostly concerns adding validity checking to
      ensure that VDQ is never used in the type of a term (as permitting
      this would require full-spectrum dependent types). This is
      accomplished by:
      
      * Adding a `vdqAllowed` predicate to `TcValidity`.
      * Introducing `splitLHsSigmaTyInvis`, a variant of `splitLHsSigmaTy`
        that only splits invisible `forall`s. This function is used in
        certain places (e.g., in instance declarations) to ensure that GHC
        doesn't try to split visible `forall`s (e.g., if it tried splitting
        `instance forall a -> Show (Blah a)`, then GHC would mistakenly
        allow that declaration!)
      
      This also updates Template Haskell by introducing a new `ForallVisT`
      constructor to `Type`.
      
      Fixes #16326. Also fixes #15658 by documenting this feature in the
      users' guide.
      c26d299d
  4. 27 Feb, 2019 1 commit
    • Vladislav Zavialov's avatar
      Treat kind/type variables identically, demolish FKTV · 5bc195b1
      Vladislav Zavialov authored
      Implements GHC Proposal #24: .../ghc-proposals/blob/master/proposals/0024-no-kind-vars.rst
      Fixes Trac #16334, Trac #16315
      
      With this patch, scoping rules for type and kind variables have been
      unified: kind variables no longer receieve special treatment. This
      simplifies both the language and the implementation.
      
      User-facing changes
      -------------------
      
      * Kind variables are no longer implicitly quantified when an explicit
        forall is used:
      
          p ::             Proxy (a :: k)    -- still accepted
          p :: forall k a. Proxy (a :: k)    -- still accepted
          p :: forall   a. Proxy (a :: k)    -- no longer accepted
      
        In other words, now we adhere to the "forall-or-nothing" rule more
        strictly.
      
        Related function: RnTypes.rnImplicitBndrs
      
      * The -Wimplicit-kind-vars warning has been deprecated.
      
      * Kind variables are no longer implicitly quantified in constructor
        declarations:
      
          data T a        = T1 (S (a :: k) | forall (b::k). T2 (S b)  -- no longer accepted
          data T (a :: k) = T1 (S (a :: k) | forall (b::k). T2 (S b)  -- still accepted
      
        Related function: RnTypes.extractRdrKindSigVars
      
      * Implicitly quantified kind variables are no longer put in front of
        other variables:
      
          f :: Proxy (a :: k) -> Proxy (b :: j)
      
          f :: forall k j (a :: k) (b :: j). Proxy a -> Proxy b   -- old order
          f :: forall k (a :: k) j (b :: j). Proxy a -> Proxy b   -- new order
      
        This is a breaking change for users of TypeApplications. Note that
        we still respect the dpendency order: 'k' before 'a', 'j' before 'b'.
        See "Ordering of specified variables" in the User's Guide.
      
        Related function: RnTypes.rnImplicitBndrs
      
      * In type synonyms and type family equations, free variables on the RHS
        are no longer implicitly quantified unless used in an outermost kind
        annotation:
      
          type T = Just (Nothing :: Maybe a)         -- no longer accepted
          type T = Just Nothing :: Maybe (Maybe a)   -- still accepted
      
        The latter form is a workaround due to temporary lack of an explicit
        quantification method. Ideally, we would write something along these
        lines:
      
          type T @a = Just (Nothing :: Maybe a)
      
        Related function: RnTypes.extractHsTyRdrTyVarsKindVars
      
      * Named wildcards in kinds are fixed (Trac #16334):
      
          x :: (Int :: _t)    -- this compiles, infers (_t ~ Type)
      
        Related function: RnTypes.partition_nwcs
      
      Implementation notes
      --------------------
      
      * One of the key changes is the removal of FKTV in RnTypes:
      
        - data FreeKiTyVars = FKTV { fktv_kis    :: [Located RdrName]
        -                          , fktv_tys    :: [Located RdrName] }
        + type FreeKiTyVars = [Located RdrName]
      
        We used to keep track of type and kind variables separately, but
        now that they are on equal footing when it comes to scoping, we
        can put them in the same list.
      
      * extract_lty and family are no longer parametrized by TypeOrKind,
        as we now do not distinguish kind variables from type variables.
      
      * PatSynExPE and the related Note [Pattern synonym existentials do not scope]
        have been removed (Trac #16315). With no implicit kind quantification,
        we can no longer trigger the error.
      
      * reportFloatingKvs and the related Note [Free-floating kind vars]
        have been removed. With no implicit kind quantification,
        we can no longer trigger the error.
      5bc195b1
  5. 24 Feb, 2019 1 commit
    • Simon Peyton Jones's avatar
      Add AnonArgFlag to FunTy · 6cce36f8
      Simon Peyton Jones authored
      The big payload of this patch is:
      
        Add an AnonArgFlag to the FunTy constructor
        of Type, so that
          (FunTy VisArg   t1 t2) means (t1 -> t2)
          (FunTy InvisArg t1 t2) means (t1 => t2)
      
      The big payoff is that we have a simple, local test to make
      when decomposing a type, leading to many fewer calls to
      isPredTy. To me the code seems a lot tidier, and probably
      more efficient (isPredTy has to take the kind of the type).
      
      See Note [Function types] in TyCoRep.
      
      There are lots of consequences
      
      * I made FunTy into a record, so that it'll be easier
        when we add a linearity field, something that is coming
        down the road.
      
      * Lots of code gets touched in a routine way, simply because it
        pattern matches on FunTy.
      
      * I wanted to make a pattern synonym for (FunTy2 arg res), which
        picks out just the argument and result type from the record. But
        alas the pattern-match overlap checker has a heart attack, and
        either reports false positives, or takes too long.  In the end
        I gave up on pattern synonyms.
      
        There's some commented-out code in TyCoRep that shows what I
        wanted to do.
      
      * Much more clarity about predicate types, constraint types
        and (in particular) equality constraints in kinds.  See TyCoRep
        Note [Types for coercions, predicates, and evidence]
        and Note [Constraints in kinds].
      
        This made me realise that we need an AnonArgFlag on
        AnonTCB in a TyConBinder, something that was really plain
        wrong before. See TyCon Note [AnonTCB InivsArg]
      
      * When building function types we must know whether we
        need VisArg (mkVisFunTy) or InvisArg (mkInvisFunTy).
        This turned out to be pretty easy in practice.
      
      * Pretty-printing of types, esp in IfaceType, gets
        tidier, because we were already recording the (->)
        vs (=>) distinction in an ad-hoc way.  Death to
        IfaceFunTy.
      
      * mkLamType needs to keep track of whether it is building
        (t1 -> t2) or (t1 => t2).  See Type
        Note [mkLamType: dictionary arguments]
      
      Other minor stuff
      
      * Some tidy-up in validity checking involving constraints;
        Trac #16263
      6cce36f8
  6. 12 Feb, 2019 1 commit
    • Ryan Scott's avatar
      Fix #16293 by cleaning up Proxy# infelicities · 012257c1
      Ryan Scott authored
      This bug fixes three problems related to `Proxy#`/`proxy#`:
      
      1. Reifying it with TH claims that the `Proxy#` type constructor has
         two arguments, but that ought to be one for consistency with
         TH's treatment for other primitive type constructors like `(->)`.
         This was fixed by just returning the number of
         `tyConVisibleTyVars` instead of using `tyConArity` (which includes
         invisible arguments).
      2. The role of `Proxy#`'s visible argument was hard-coded as nominal.
         Easily fixed by changing it to phantom.
      3. The visibility of `proxy#`'s kind argument was specified, which
         is different from the `Proxy` constructor (which treats it as
         inferred). Some minor refactoring in `proxyHashId` fixed ths up.
      
         Along the way, I had to introduce a `mkSpecForAllTy` function, so
         I did some related Haddock cleanup in `Type`, where that function
         lives.
      012257c1
  7. 10 Feb, 2019 1 commit
    • Matthew Pickering's avatar
      Capture and simplify constraints arising from running typed splices · a48753bd
      Matthew Pickering authored
      This fixes a regression caused by #15471 where splicing in a trivial
      program such as `[|| return () ||]` would fail as the dictionary for
      `return` would never get bound in the module containing the splice.
      
      Arguably this is symptomatic of a major problem affecting TTH where we
      serialise renamed asts and then retype check them. The reference to the
      dictionary should be fully determined at the quote site so that splicing
      doesn't have to solve any implicits at all. It's a coincidence this
      works due to coherence but see #15863 and #15865 for examples where
      things do go very wrong.
      
      Fixes #16195
      a48753bd
  8. 06 Feb, 2019 1 commit
  9. 11 Jan, 2019 1 commit
  10. 03 Jan, 2019 1 commit
    • My Nguyen's avatar
      Visible kind application · 17bd1635
      My Nguyen authored
      Summary:
      This patch implements visible kind application (GHC Proposal 15/#12045), as well as #15360 and #15362.
      It also refactors unnamed wildcard handling, and requires that type equations in type families in Template Haskell be
      written with full type on lhs. PartialTypeSignatures are on and warnings are off automatically with visible kind
      application, just like in term-level.
      
      There are a few remaining issues with this patch, as documented in
      ticket #16082.
      
      Includes a submodule update for Haddock.
      
      Test Plan: Tests T12045a/b/c/TH1/TH2, T15362, T15592a
      
      Reviewers: simonpj, goldfire, bgamari, alanz, RyanGlScott, Iceland_jack
      
      Subscribers: ningning, Iceland_jack, RyanGlScott, int-index, rwbarton, mpickering, carter
      
      GHC Trac Issues: `#12045`, `#15362`, `#15592`, `#15788`, `#15793`, `#15795`, `#15797`, `#15799`, `#15801`, `#15807`, `#15816`
      
      Differential Revision: https://phabricator.haskell.org/D5229
      17bd1635
  11. 03 Dec, 2018 1 commit
    • Simon Peyton Jones's avatar
      Introduce tcTypeKind, and use it · 03d48526
      Simon Peyton Jones authored
      In the type checker Constraint and * are distinct; and the function
      that takes the kind of a type should respect that distinction
      (Trac #15971).
      
      This patch implements the change:
      
      * Introduce Type.tcTypeKind, and use it throughout the type
        inference engine
      
      * Add new Note [Kinding rules for types] for the kinding
        rules, especially for foralls.
      
      * Redefine
          isPredTy ty = tcIsConstraintKind (tcTypeKind ty)
        (it had a much more complicated definition before)
      
      Some miscellaneous refactoring
      
      * Get rid of TyCoRep.isTYPE, Kind.isTYPEApp,
        in favour of TyCoRep.kindRep, kindRep_maybe
      
      * Rename Type.getRuntimeRepFromKind_maybe
        to getRuntimeRep_maybe
      
      I did some spot-checks on compiler perf, and it really doesn't
      budge (as expected).
      03d48526
  12. 29 Nov, 2018 1 commit
    • Simon Peyton Jones's avatar
      Taming the Kind Inference Monster · 2257a86d
      Simon Peyton Jones authored
      My original goal was (Trac #15809) to move towards using level numbers
      as the basis for deciding which type variables to generalise, rather
      than searching for the free varaibles of the environment.  However
      it has turned into a truly major refactoring of the kind inference
      engine.
      
      Let's deal with the level-numbers part first:
      
      * Augment quantifyTyVars to calculate the type variables to
        quantify using level numbers, and compare the result with
        the existing approach.  That is; no change in behaviour,
        just a WARNing if the two approaches give different answers.
      
      * To do this I had to get the level number right when calling
        quantifyTyVars, and this entailed a bit of care, especially
        in the code for kind-checking type declarations.
      
      * However, on the way I was able to eliminate or simplify
        a number of calls to solveEqualities.
      
      This work is incomplete: I'm not /using/ level numbers yet.
      When I subsequently get rid of any remaining WARNings in
      quantifyTyVars, that the level-number answers differ from
      the current answers, then I can rip out the current
      "free vars of the environment" stuff.
      
      Anyway, this led me into deep dive into kind inference for type and
      class declarations, which is an increasingly soggy part of GHC.
      Richard already did some good work recently in
      
         commit 5e45ad10
         Date:   Thu Sep 13 09:56:02 2018 +0200
      
          Finish fix for #14880.
      
          The real change that fixes the ticket is described in
          Note [Naughty quantification candidates] in TcMType.
      
      but I kept turning over stones. So this patch has ended up
      with a pretty significant refactoring of that code too.
      
      Kind inference for types and classes
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      
      * Major refactoring in the way we generalise the inferred kind of
        a TyCon, in kcTyClGroup.  Indeed, I made it into a new top-level
        function, generaliseTcTyCon.  Plus a new Note to explain it
        Note [Inferring kinds for type declarations].
      
      * We decided (Trac #15592) not to treat class type variables specially
        when dealing with Inferred/Specified/Required for associated types.
        That simplifies things quite a bit. I also rewrote
        Note [Required, Specified, and Inferred for types]
      
      * Major refactoring of the crucial function kcLHsQTyVars:
        I split it into
             kcLHsQTyVars_Cusk  and  kcLHsQTyVars_NonCusk
        because the two are really quite different. The CUSK case is
        almost entirely rewritten, and is much easier because of our new
        decision not to treat the class variables specially
      
      * I moved all the error checks from tcTyClTyVars (which was a bizarre
        place for it) into generaliseTcTyCon and/or the CUSK case of
        kcLHsQTyVars.  Now tcTyClTyVars is extremely simple.
      
      * I got rid of all the all the subtleties in tcImplicitTKBndrs. Indeed
        now there is no difference between tcImplicitTKBndrs and
        kcImplicitTKBndrs; there is now a single bindImplicitTKBndrs.
        Same for kc/tcExplicitTKBndrs.  None of them monkey with level
        numbers, nor build implication constraints.  scopeTyVars is gone
        entirely, as is kcLHsQTyVarBndrs. It's vastly simpler.
      
        I found I could get rid of kcLHsQTyVarBndrs entirely, in favour of
        the bnew bindExplicitTKBndrs.
      
      Quantification
      ~~~~~~~~~~~~~~
      * I now deal with the "naughty quantification candidates"
        of the previous patch in candidateQTyVars, rather than in
        quantifyTyVars; see Note [Naughty quantification candidates]
        in TcMType.
      
        I also killed off closeOverKindsCQTvs in favour of the same
        strategy that we use for tyCoVarsOfType: namely, close over kinds
        at the occurrences.
      
        And candidateQTyVars no longer needs a gbl_tvs argument.
      
      * Passing the ContextKind, rather than the expected kind itself,
        to tc_hs_sig_type_and_gen makes it easy to allocate the expected
        result kind (when we are in inference mode) at the right level.
      
      Type families
      ~~~~~~~~~~~~~~
      * I did a major rewrite of the impenetrable tcFamTyPats. The result
        is vastly more comprehensible.
      
      * I got rid of kcDataDefn entirely, quite a big function.
      
      * I re-did the way that checkConsistentFamInst works, so
        that it allows alpha-renaming of invisible arguments.
      
      * The interaction of kind signatures and family instances is tricky.
          Type families: see Note [Apparently-nullary families]
          Data families: see Note [Result kind signature for a data family instance]
                         and Note [Eta-reduction for data families]
      
      * The consistent instantation of an associated type family is tricky.
        See Note [Checking consistent instantiation] and
            Note [Matching in the consistent-instantation check]
        in TcTyClsDecls.  It's now checked in TcTyClsDecls because that is
        when we have the relevant info to hand.
      
      * I got tired of the compromises in etaExpandFamInst, so I did the
        job properly by adding a field cab_eta_tvs to CoAxBranch.
        See Coercion.etaExpandCoAxBranch.
      
      tcInferApps and friends
      ~~~~~~~~~~~~~~~~~~~~~~~
      * I got rid of the mysterious and horrible ClsInstInfo argument
        to tcInferApps, checkExpectedKindX, and various checkValid
        functions.  It was horrible!
      
      * I got rid of [Type] result of tcInferApps.  This list was used
        only in tcFamTyPats, when checking the LHS of a type instance;
        and if there is a cast in the middle, the list is meaningless.
        So I made tcInferApps simpler, and moved the complexity
        (not much) to tcInferApps.
      
        Result: tcInferApps is now pretty comprehensible again.
      
      * I refactored the many function in TcMType that instantiate skolems.
      
      Smaller things
      
      * I rejigged the error message in checkValidTelescope; I think it's
        quite a bit better now.
      
      * checkValidType was not rejecting constraints in a kind signature
           forall (a :: Eq b => blah). blah2
        That led to further errors when we then do an ambiguity check.
        So I make checkValidType reject it more aggressively.
      
      * I killed off quantifyConDecl, instead calling kindGeneralize
        directly.
      
      * I fixed an outright bug in tyCoVarsOfImplic, where we were not
        colleting the tyvar of the kind of the skolems
      
      * Renamed ClsInstInfo to AssocInstInfo, and made it into its
        own data type
      
      * Some fiddling around with pretty-printing of family
        instances which was trickier than I thought.  I wanted
        wildcards to print as plain "_" in user messages, although
        they each need a unique identity in the CoAxBranch.
      
      Some other oddments
      
      * Refactoring around the trace messages from reportUnsolved.
      * A bit of extra tc-tracing in TcHsSyn.commitFlexi
      
      This patch fixes a raft of bugs, and includes tests for them.
      
       * #14887
       * #15740
       * #15764
       * #15789
       * #15804
       * #15817
       * #15870
       * #15874
       * #15881
      2257a86d
  13. 22 Nov, 2018 2 commits
    • Ryan Scott's avatar
      Fix #15852 by eta expanding data family instance RHSes, too · 014d6c1f
      Ryan Scott authored
      When I defined `etaExpandFamInstLHS`, I blatantly forgot
      to eta expand the RHSes of data family instances. (Actually, I
      claimed that they didn't //need// to be eta expanded. I'm not sure
      what I was thinking.)
      
      This fixes the issue by changing `etaExpandFamInstLHS` to
      `etaExpandFamInst` and, well, making it actually eta expand the RHS.
      
      Test Plan: make test TEST=T15852
      
      Reviewers: goldfire, bgamari
      
      Reviewed By: goldfire
      
      Subscribers: rwbarton, carter
      
      GHC Trac Issues: #15852
      
      Differential Revision: https://phabricator.haskell.org/D5328
      014d6c1f
    • Sylvain Henry's avatar
      Rename literal constructors · 13bb4bf4
      Sylvain Henry authored
      In a previous patch we replaced some built-in literal constructors
      (MachInt, MachWord, etc.) with a single LitNumber constructor.
      
      In this patch we replace the `Mach` prefix of the remaining constructors
      with `Lit` for consistency (e.g., LitChar, LitLabel, etc.).
      
      Sadly the name `LitString` was already taken for a kind of FastString
      and it would become misleading to have both `LitStr` (literal
      constructor renamed after `MachStr`) and `LitString` (FastString
      variant). Hence this patch renames the FastString variant `PtrString`
      (which is more accurate) and the literal string constructor now uses the
      least surprising `LitString` name.
      
      Both `Literal` and `LitString/PtrString` have recently seen breaking
      changes so doing this kind of renaming now shouldn't harm much.
      
      Reviewers: hvr, goldfire, bgamari, simonmar, jrtc27, tdammers
      
      Subscribers: tdammers, rwbarton, thomie, carter
      
      Differential Revision: https://phabricator.haskell.org/D4881
      13bb4bf4
  14. 08 Nov, 2018 1 commit
    • Ryan Scott's avatar
      Fix #15845 by defining etaExpandFamInstLHS and using it · 63a81707
      Ryan Scott authored
      Summary:
      Both #9692 and #14179 were caused by GHC being careless
      about using eta-reduced data family instance axioms. Each of those
      tickets were fixed by manually whipping up some code to eta-expand
      the axioms. The same sort of issue has now caused #15845, so I
      figured it was high time to factor out the code that each of these
      fixes have in common.
      
      This patch introduces the `etaExpandFamInstLHS` function, which takes
      a family instance's type variables, LHS types, and RHS type, and
      returns type variables and LHS types that have been eta-expanded if
      necessary, in the case of a data family instance. (If it's a type
      family instance, `etaExpandFamInstLHS` just returns the supplied type
      variables and LHS types unchanged).
      
      Along the way, I noticed that many references to
      `Note [Eta reduction for data families]` (in `FamInstEnv`) had
      slightly bitrotted (they either referred to a somewhat different
      name, or claimed that the Note lived in a different module), so
      I took the liberty of cleaning those up.
      
      Test Plan: make test TEST="T9692 T15845"
      
      Reviewers: goldfire, bgamari
      
      Reviewed By: goldfire
      
      Subscribers: rwbarton, carter
      
      GHC Trac Issues: #15845
      
      Differential Revision: https://phabricator.haskell.org/D5294
      63a81707
  15. 27 Oct, 2018 1 commit
    • mayac's avatar
      More explicit foralls (GHC Proposal 0007) · 512eeb9b
      mayac authored
      Allow the user to explicitly bind type/kind variables in type and data
      family instances (including associated instances), closed type family
      equations, and RULES pragmas. Follows the specification of GHC
      Proposal 0007, also fixes #2600. Advised by Richard Eisenberg.
      
      This modifies the Template Haskell AST -- old code may break!
      
      Other Changes:
      - convert HsRule to a record
      - make rnHsSigWcType more general
      - add repMaybe to DsMeta
      
      Includes submodule update for Haddock.
      
      Test Plan: validate
      
      Reviewers: goldfire, bgamari, alanz
      
      Subscribers: simonpj, RyanGlScott, goldfire, rwbarton,
                   thomie, mpickering, carter
      
      GHC Trac Issues: #2600, #14268
      
      Differential Revision: https://phabricator.haskell.org/D4894
      512eeb9b
  16. 26 Oct, 2018 1 commit
    • Simon Peyton Jones's avatar
      De-monadise the 'extract' functions in RnTypes · e6bf96c9
      Simon Peyton Jones authored
      As Trac #15765 says, Once upon a time, the extract functions
      at the bottom of RnTypes were pure. Then, along came -XTypeInType,
      which needed to do a check in these functions for users mixing
      type variables with kind variables.
      
      Now, however, with -XTypeInType gone again, we no longer
      do this check. Thus, there is no reason to keep these
      functions monadic.
      e6bf96c9
  17. 24 Oct, 2018 1 commit
    • Ryan Scott's avatar
      Fix #15792 by not reifying invisible arguments in AppTys · bfd93f90
      Ryan Scott authored
      Summary:
      The `reifyType` function in `TcSplice` is carefully designed
      to avoid reifying visible arguments to `TyConApp`s. However, the same
      care was not given towards the `AppTy` case, which lead to #15792.
      
      This patch changes to the `AppTy` case of `reifyType` so that it
      consults the kind of the function type to determine which of the
      argument types are invisible (and therefore should be dropped) during
      reification. This required crafting a variant of `tyConArgFlags`,
      which I dubbed `appTyArgFlags`, that accept an arbitrary function
      `Type` instead of a `TyCon`.
      
      Test Plan: make test TEST=T15792
      
      Reviewers: goldfire, bgamari, simonpj
      
      Reviewed By: simonpj
      
      Subscribers: simonpj, rwbarton, carter
      
      GHC Trac Issues: #15792
      
      Differential Revision: https://phabricator.haskell.org/D5252
      bfd93f90
  18. 27 Sep, 2018 1 commit
    • Simon Marlow's avatar
      Fix for recover with -fexternal-interpreter (#15418) · d00c3086
      Simon Marlow authored
      Summary:
      When using -fexternal-interpreter, recover was not treating a Q
      compuation that simply registered an error with addErrTc as failing.
      
      Test Plan:
      New unit tests:
      * T15418 is the repro from in the ticket
      * TH_recover_warns is a new test to ensure that we're keeping warnings when
        the body of recover succeeds.
      
      Reviewers: bgamari, RyanGlScott, angerman, goldfire, erikd
      
      Subscribers: rwbarton, carter
      
      GHC Trac Issues: #15418
      
      Differential Revision: https://phabricator.haskell.org/D5185
      d00c3086
  19. 15 Sep, 2018 1 commit
    • Ningning Xie's avatar
      Coercion Quantification · ea5ade34
      Ningning Xie authored
      This patch corresponds to #15497.
      
      According to https://ghc.haskell.org/trac/ghc/wiki/DependentHaskell/Phase2,
       we would like to have coercion quantifications back. This will
      allow us to migrate (~#) to be homogeneous, instead of its current
      heterogeneous definition. This patch is (lots of) plumbing only. There
      should be no user-visible effects.
      
      An overview of changes:
      
      - Both `ForAllTy` and `ForAllCo` can quantify over coercion variables,
      but only in *Core*. All relevant functions are updated accordingly.
      - Small changes that should be irrelevant to the main task:
          1. removed dead code `mkTransAppCo` in Coercion
          2. removed out-dated Note Computing a coercion kind and
             roles in Coercion
          3. Added `Eq4` in Note Respecting definitional equality in
             TyCoRep, and updated `mkCastTy` accordingly.
          4. Various updates and corrections of notes and typos.
      - Haddock submodule needs to be changed too.
      
      Acknowledgments:
      This work was completed mostly during Ningning Xie's Google Summer
      of Code, sponsored by Google. It was advised by Richard Eisenberg,
      supported by NSF grant 1704041.
      
      Test Plan: ./validate
      
      Reviewers: goldfire, simonpj, bgamari, hvr, erikd, simonmar
      
      Subscribers: RyanGlScott, monoidal, rwbarton, carter
      
      GHC Trac Issues: #15497
      
      Differential Revision: https://phabricator.haskell.org/D5054
      ea5ade34
  20. 14 Sep, 2018 1 commit
    • Michael Sloan's avatar
      Add support for ImplicitParams and RecursiveDo in TH · 9c6b7493
      Michael Sloan authored
      Summary:
      This adds TH support for the ImplicitParams and RecursiveDo extensions.
      
      I'm submitting this as one review because I cannot cleanly make
      the two commits independent.
      
      Initially, my goal was just to add ImplicitParams support, and
      I found that reasonably straightforward, so figured I might
      as well use my newfound knowledge to address some other TH omissions.
      
      Test Plan: Validate
      
      Reviewers: goldfire, austin, bgamari, RyanGlScott
      
      Reviewed By: RyanGlScott
      
      Subscribers: carter, RyanGlScott, thomie
      
      GHC Trac Issues: #1262
      
      Differential Revision: https://phabricator.haskell.org/D1979
      9c6b7493
  21. 31 Aug, 2018 1 commit
    • Simon Peyton Jones's avatar
      Remove knot-tying bug in TcHsSyn.zonkTyVarOcc · 565ef4cc
      Simon Peyton Jones authored
      There was a subtle knot-tying bug in TcHsSyn.zonkTyVarOcc, revealed
      in Trac #15552.
      
      I fixed it by
      
      * Eliminating the short-circuiting optimisation in zonkTyVarOcc,
        instead adding a finite map to get sharing of zonked unification
        variables.
      
        See Note [Sharing when zonking to Type] in TcHsSyn
      
      * On the way I /added/ the short-circuiting optimisation to
        TcMType.zonkTcTyVar, which has no such problem.  This turned
        out (based on non-systematic measurements) to be a modest win.
      
        See Note [Sharing in zonking] in TcMType
      
      On the way I renamed some of the functions in TcHsSyn:
      
      * Ones ending in "X" (like zonkTcTypeToTypeX) take a ZonkEnv
      
      * Ones that do not end in "x" (like zonkTcTypeToType), don't.
        Instead they whiz up an empty ZonkEnv.
      565ef4cc
  22. 27 Aug, 2018 1 commit
    • Ryan Scott's avatar
      Don't reify redundant class method tyvars/contexts · 6e765aeb
      Ryan Scott authored
      Summary:
      Currently, reifying classes produces class methods with
      redundant tyvars and class contexts in their type signatures, such
      as in the following:
      
      ```lang=haskell
      class C a where
        method :: forall a. C a => a
      ```
      
      Fixing this is very straightforward: just apply `tcSplitMethodTy` to
      the type of each class method to lop off the redundant parts.
      
      It's possible that this could break some TH code in the wild that
      assumes the existence of these tyvars and class contexts, so I'll
      advertise this change in the release notes just to be safe.
      
      Test Plan: make test TEST="TH_reifyDecl1 T9064 T10891 T14888"
      
      Reviewers: goldfire, bgamari, simonpj
      
      Reviewed By: simonpj
      
      Subscribers: simonpj, rwbarton, carter
      
      GHC Trac Issues: #15551
      
      Differential Revision: https://phabricator.haskell.org/D5088
      6e765aeb
  23. 21 Aug, 2018 1 commit
    • Andreas Klebinger's avatar
      Replace most occurences of foldl with foldl'. · 09c1d5af
      Andreas Klebinger authored
      This patch adds foldl' to GhcPrelude and changes must occurences
      of foldl to foldl'. This leads to better performance especially
      for quick builds where GHC does not perform strictness analysis.
      
      It does change strictness behaviour when we use foldl' to turn
      a argument list into function applications. But this is only a
      drawback if code looks ONLY at the last argument but not at the first.
      And as the benchmarks show leads to fewer allocations in practice
      at O2.
      
      Compiler performance for Nofib:
      
      O2 Allocations:
              -1 s.d.                -----            -0.0%
              +1 s.d.                -----            -0.0%
              Average                -----            -0.0%
      
      O2 Compile Time:
              -1 s.d.                -----            -2.8%
              +1 s.d.                -----            +1.3%
              Average                -----            -0.8%
      
      O0 Allocations:
              -1 s.d.                -----            -0.2%
              +1 s.d.                -----            -0.1%
              Average                -----            -0.2%
      
      Test Plan: ci
      
      Reviewers: goldfire, bgamari, simonmar, tdammers, monoidal
      
      Reviewed By: bgamari, monoidal
      
      Subscribers: tdammers, rwbarton, thomie, carter
      
      Differential Revision: https://phabricator.haskell.org/D4929
      09c1d5af
  24. 02 Aug, 2018 1 commit
    • Richard Eisenberg's avatar
      Remove decideKindGeneralisationPlan · c955a514
      Richard Eisenberg authored
      TypeInType came with a new function: decideKindGeneralisationPlan.
      This type-level counterpart to the term-level decideGeneralisationPlan
      chose whether or not a kind should be generalized. The thinking was
      that if `let` should not be generalized, then kinds shouldn't either
      (under the same circumstances around -XMonoLocalBinds).
      
      However, this is too conservative -- the situation described in the
      motivation for "let should be be generalized" does not occur in types.
      
      This commit thus removes decideKindGeneralisationPlan, always
      generalizing.
      
      One consequence is that tc_hs_sig_type_and_gen no longer calls
      solveEqualities, which reports all unsolved constraints, instead
      relying on the solveLocalEqualities in tcImplicitTKBndrs. An effect
      of this is that reporing kind errors gets delayed more frequently.
      This seems to be a net benefit in error reporting; often, alongside
      a kind error, the type error is now reported (and users might find
      type errors easier to understand).
      
      Some of these errors ended up at the top level, where it was
      discovered that the GlobalRdrEnv containing the definitions in the
      local module was not in the TcGblEnv, and thus errors were reported
      with qualified names unnecessarily. This commit rejiggers some of
      the logic around captureTopConstraints accordingly.
      
      One error message (typecheck/should_fail/T1633)
      is a regression, mentioning the name of a default method. However,
      that problem is already reported as #10087, its solution is far from
      clear, and so I'm not addressing it here.
      
      This commit fixes #15141. As it's an internal refactor, there is
      no concrete test case for it.
      
      Along the way, we no longer need the hsib_closed field of
      HsImplicitBndrs (it was used only in decideKindGeneralisationPlan)
      and so it's been removed, simplifying the datatype structure.
      
      Along the way, I removed code in the validity checker that looks
      at coercions. This isn't related to this patch, really (though
      it was, at one point), but it's an improvement, so I kept it.
      
      This updates the haddock submodule.
      c955a514
  25. 27 Jul, 2018 1 commit
  26. 25 Jul, 2018 1 commit
    • Simon Peyton Jones's avatar
      Treat isConstraintKind more consistently · c5d31df7
      Simon Peyton Jones authored
      It turned out that we were not being consistent
      about our use of isConstraintKind.
      
      It's delicate, because the typechecker treats Constraint and Type as
      /distinct/, whereas they are the /same/ in the rest of the compiler
      (Trac #11715).
      
      And had it wrong, which led to Trac #15412.  This patch does the
      following:
      
      * Rename isConstraintKind      to tcIsConstraintKind
               returnsConstraintKind to tcReturnsConstraintKind
        to emphasise that they use the 'tcView' view of types.
      
      * Move these functions, and some related ones (tcIsLiftedTypeKind),
        from Kind.hs, to group together in Type.hs, alongside isPredTy.
      
      It feels very unsatisfactory that these 'tcX' functions live in Type,
      but it happens because isPredTy is called later in the compiler
      too.  But it's a consequence of the 'Constraint vs Type' dilemma.
      c5d31df7
  27. 18 Jun, 2018 1 commit
    • Simon Peyton Jones's avatar
      Two small refactorings · 850ae8c5
      Simon Peyton Jones authored
      * Define Type.substTyVarBndrs, and use it
      
      * Rename substTyVarBndrCallback to substTyVarBndrUsing,
        and other analogous higher order functions.  I kept
        stumbling over the name.
      850ae8c5
  28. 14 Jun, 2018 1 commit
    • Vladislav Zavialov's avatar
      Embrace -XTypeInType, add -XStarIsType · d650729f
      Vladislav Zavialov authored
      Summary:
      Implement the "Embrace Type :: Type" GHC proposal,
      .../ghc-proposals/blob/master/proposals/0020-no-type-in-type.rst
      
      GHC 8.0 included a major change to GHC's type system: the Type :: Type
      axiom. Though casual users were protected from this by hiding its
      features behind the -XTypeInType extension, all programs written in GHC
      8+ have the axiom behind the scenes. In order to preserve backward
      compatibility, various legacy features were left unchanged. For example,
      with -XDataKinds but not -XTypeInType, GADTs could not be used in types.
      Now these restrictions are lifted and -XTypeInType becomes a redundant
      flag that will be eventually deprecated.
      
      * Incorporate the features currently in -XTypeInType into the
        -XPolyKinds and -XDataKinds extensions.
      * Introduce a new extension -XStarIsType to control how to parse * in
        code and whether to print it in error messages.
      
      Test Plan: Validate
      
      Reviewers: goldfire, hvr, bgamari, alanz, simonpj
      
      Reviewed By: goldfire, ...
      d650729f
  29. 03 Jun, 2018 1 commit
  30. 27 Apr, 2018 1 commit
    • Alan Zimmerman's avatar
      TTG : complete for balance of hsSyn AST · c3823cba
      Alan Zimmerman authored
      Summary:
      - remove PostRn/PostTc fields
      - remove the HsVect In/Out distinction for Type, Class and Instance
      - remove PlaceHolder in favour of NoExt
      - Simplify OutputableX constraint
      
      Updates haddock submodule
      
      Test Plan: ./validate
      
      Reviewers: goldfire, bgamari
      
      Subscribers: goldfire, thomie, mpickering, carter
      
      Differential Revision: https://phabricator.haskell.org/D4625
      c3823cba
  31. 09 Apr, 2018 1 commit
  32. 01 Apr, 2018 1 commit
    • Richard Eisenberg's avatar
      Track type variable scope more carefully. · faec8d35
      Richard Eisenberg authored
      The main job of this commit is to track more accurately the scope
      of tyvars introduced by user-written foralls. For example, it would
      be to have something like this:
      
        forall a. Int -> (forall k (b :: k). Proxy '[a, b]) -> Bool
      
      In that type, a's kind must be k, but k isn't in scope. We had a
      terrible way of doing this before (not worth repeating or describing
      here, but see the old tcImplicitTKBndrs and friends), but now
      we have a principled approach: make an Implication when kind-checking
      a forall. Doing so then hooks into the existing machinery for
      preventing skolem-escape, performing floating, etc. This also means
      that we bump the TcLevel whenever going into a forall.
      
      The new behavior is done in TcHsType.scopeTyVars, but see also
      TcHsType.tc{Im,Ex}plicitTKBndrs, which have undergone significant
      rewriting. There are several Notes near there to guide you. Of
      particular interest there is that Implication constraints can now
      have skolems that are out of order; this situation is reported in
      TcErrors.
      
      A major consequence of this is a slightly tweaked process for type-
      checking type declarations. The new Note [Use SigTvs in kind-checking
      pass] in TcTyClsDecls lays it out.
      
      The error message for dependent/should_fail/TypeSkolEscape has become
      noticeably worse. However, this is because the code in TcErrors goes to
      some length to preserve pre-8.0 error messages for kind errors. It's time
      to rip off that plaster and get rid of much of the kind-error-specific
      error messages. I tried this, and doing so led to a lovely error message
      for TypeSkolEscape. So: I'm accepting the error message quality regression
      for now, but will open up a new ticket to fix it, along with a larger
      error-message improvement I've been pondering. This applies also to
      dependent/should_fail/{BadTelescope2,T14066,T14066e}, polykinds/T11142.
      
      Other minor changes:
       - isUnliftedTypeKind didn't look for tuples and sums. It does now.
      
       - check_type used check_arg_type on both sides of an AppTy. But the left
         side of an AppTy isn't an arg, and this was causing a bad error message.
         I've changed it to use check_type on the left-hand side.
      
       - Some refactoring around when we print (TYPE blah) in error messages.
         The changes decrease the times when we do so, to good effect.
         Of course, this is still all controlled by
         -fprint-explicit-runtime-reps
      
      Fixes #14066 #14749
      
      Test cases: dependent/should_compile/{T14066a,T14749},
                  dependent/should_fail/T14066{,c,d,e,f,g,h}
      faec8d35
  33. 25 Mar, 2018 1 commit
    • Alec Theriault's avatar
      Support adding objects from TH · ceb91477
      Alec Theriault authored
      The user facing TH interface changes are:
      
        * 'addForeignFile' is renamed to 'addForeignSource'
        * 'qAddForeignFile'/'addForeignFile' now expect 'FilePath's
        * 'RawObject' is now a constructor for 'ForeignSrcLang'
        * 'qAddTempFile'/'addTempFile' let you request a temporary file
          from the compiler.
      
      Test Plan: unsure about this, added a TH test
      
      Reviewers: goldfire, bgamari, angerman
      
      Reviewed By: bgamari, angerman
      
      Subscribers: hsyl20, mboes, carter, simonmar, bitonic, ljli, rwbarton, thomie
      
      GHC Trac Issues: #14298
      
      Differential Revision: https://phabricator.haskell.org/D4217
      ceb91477
  34. 21 Mar, 2018 1 commit
    • Ryan Scott's avatar
      Fix #14869 by being more mindful of Type vs. Constraint · 49ac3f0f
      Ryan Scott authored
      Summary:
      Before, we were using `isLiftedTypeKind` in `reifyType`
      before checking if a type was `Constraint`. But as it turns out,
      `isLiftedTypeKind` treats `Constraint` the same as `Type`, so every
      occurrence of `Constraint` would be reified as `Type`! To make things
      worse, the documentation for `isLiftedTypeKind` stated that it
      treats `Constraint` //differently// from `Type`, which simply isn't
      true.
      
      This revises the documentation for `isLiftedTypeKind` to reflect
      reality, and defers the `isLiftedTypeKind` check in `reifyType` so
      that it does not accidentally swallow `Constraint`.
      
      Test Plan: make test TEST=T14869
      
      Reviewers: goldfire, bgamari
      
      Reviewed By: goldfire
      
      Subscribers: rwbarton, thomie, carter
      
      GHC Trac Issues: #14869
      
      Differential Revision: https://phabricator.haskell.org/D4474
      49ac3f0f
  35. 05 Mar, 2018 1 commit
    • Ryan Scott's avatar
      Fix #14888 by adding more special cases for ArrowT · 6ee831f2
      Ryan Scott authored
      Summary:
      There were previously some situations where `(->)` would
      not be desugared or reified as `ArrowT`, leading to various oddities
      such as those observed in #14888. We now uniformly treat `(->)` as
      `ArrowT` in Template Haskell–world by checking for any tycon that
      has the same name as `(->)`, and converting that to `ArrowT`.
      
      Test Plan: make test TEST=T14888
      
      Reviewers: goldfire, bgamari, simonpj
      
      Reviewed By: goldfire, simonpj
      
      Subscribers: simonpj, rwbarton, thomie, carter
      
      GHC Trac Issues: #14888
      
      Differential Revision: https://phabricator.haskell.org/D4466
      6ee831f2
  36. 21 Nov, 2017 1 commit
    • Ben Gamari's avatar
      Revert "trees that grow" work · 314bc314
      Ben Gamari authored
      As documented in #14490, the Data instances currently blow up
      compilation time by too much to stomach. Alan will continue working on
      this in a branch and we will perhaps merge to 8.2 before 8.2.1 to avoid
      having to perform painful cherry-picks in 8.2 minor releases.
      
      Reverts haddock submodule.
      
      This reverts commit 47ad6578.
      This reverts commit e3ec2e7a.
      This reverts commit 438dd1cb.
      This reverts commit 0ff152c9.
      314bc314
  37. 14 Nov, 2017 1 commit
  38. 11 Nov, 2017 1 commit
  39. 19 Oct, 2017 1 commit