1. 09 Oct, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-10-09 11:58:39 by simonpj] · 98688c6e
      simonpj authored
      -------------------------
      		GHC heart/lung transplant
      		-------------------------
      
      This major commit changes the way that GHC deals with importing
      types and functions defined in other modules, during renaming and
      typechecking.  On the way I've changed or cleaned up numerous other
      things, including many that I probably fail to mention here.
      
      Major benefit: GHC should suck in many fewer interface files when
      compiling (esp with -O).  (You can see this with -ddump-rn-stats.)
      
      It's also some 1500 lines of code shorter than before.
      
      **	So expect bugs!  I can do a 3-stage bootstrap, and run
      **	the test suite, but you may be doing stuff I havn't tested.
      ** 	Don't update if you are relying on a working HEAD.
      
      
      In particular, (a) External Core and (b) GHCi are very little tested.
      
      	But please, please DO test this version!
      
      
      	------------------------
      		Big things
      	------------------------
      
      Interface files, version control, and importing declarations
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      * There is a totally new data type for stuff that lives in interface files:
      	Original names			IfaceType.IfaceExtName
      	Types				IfaceType.IfaceType
      	Declarations (type,class,id)	IfaceSyn.IfaceDecl
      	Unfoldings			IfaceSyn.IfaceExpr
        (Previously we used HsSyn for type/class decls, and UfExpr for unfoldings.)
        The new data types are in iface/IfaceType and iface/IfaceSyn.  They are
        all instances of Binary, so they can be written into interface files.
        Previous engronkulation concering the binary instance of RdrName has
        gone away -- RdrName is not an instance of Binary any more.  Nor does
        Binary.lhs need to know about the ``current module'' which it used to,
        which made it specialised to GHC.
      
        A good feature of this is that the type checker for source code doesn't
        need to worry about the possibility that we might be typechecking interface
        file stuff.  Nor does it need to do renaming; we can typecheck direct from
        IfaceSyn, saving a whole pass (module TcIface)
      
      * Stuff from interface files is sucked in *lazily*, rather than being eagerly
        sucked in by the renamer. Instead, we use unsafeInterleaveIO to capture
        a thunk for the unfolding of an imported function (say).  If that unfolding
        is every pulled on, TcIface will scramble over the unfolding, which may
        in turn pull in the interface files of things mentioned in the unfolding.
      
        The External Package State is held in a mutable variable so that it
        can be side-effected by this lazy-sucking-in process (which may happen
        way later, e.g. when the simplifier runs).   In effect, the EPS is a kind
        of lazy memo table, filled in as we suck things in.  Or you could think
        of it as a global symbol table, populated on demand.
      
      * This lazy sucking is very cool, but it can lead to truly awful bugs. The
        intent is that updates to the symbol table happen atomically, but very bad
        things happen if you read the variable for the table, and then force a
        thunk which updates the table.  Updates can get lost that way. I regret
        this subtlety.
      
        One example of the way it showed up is that the top level of TidyPgm
        (which updates the global name cache) to be much more disciplined about
        those updates, since TidyPgm may itself force thunks which allocate new
        names.
      
      * Version numbering in interface files has changed completely, fixing
        one major bug with ghc --make.  Previously, the version of A.f changed
        only if A.f's type and unfolding was textually different.  That missed
        changes to things that A.f's unfolding mentions; which was fixed by
        eagerly sucking in all of those things, and listing them in the module's
        usage list.  But that didn't work with --make, because they might have
        been already sucked in.
      
        Now, A.f's version changes if anything reachable from A.f (via interface
        files) changes.  A module with unchanged source code needs recompiling
        only if the versions of any of its free variables changes. [This isn't
        quite right for dictionary functions and rules, which aren't mentioned
        explicitly in the source.  There are extensive comments in module MkIface,
        where all version-handling stuff is done.]
      
      * We don't need equality on HsDecls any more (because they aren't used in
        interface files).  Instead we have a specialised equality for IfaceSyn
        (eqIfDecl etc), which uses IfaceEq instead of Bool as its result type.
        See notes in IfaceSyn.
      
      * The horrid bit of the renamer that tried to predict what instance decls
        would be needed has gone entirely.  Instead, the type checker simply
        sucks in whatever instance decls it needs, when it needs them.  Easy!
      
        Similarly, no need for 'implicitModuleFVs' and 'implicitTemplateHaskellFVs'
        etc.  Hooray!
      
      
      Types and type checking
      ~~~~~~~~~~~~~~~~~~~~~~~
      * Kind-checking of types is far far tidier (new module TcHsTypes replaces
        the badly-named TcMonoType).  Strangely, this was one of my
        original goals, because the kind check for types is the Right Place to
        do type splicing, but it just didn't fit there before.
      
      * There's a new representation for newtypes in TypeRep.lhs.  Previously
        they were represented using "SourceTypes" which was a funny compromise.
        Now they have their own constructor in the Type datatype.  SourceType
        has turned back into PredType, which is what it used to be.
      
      * Instance decl overlap checking done lazily.  Consider
      	instance C Int b
      	instance C a Int
        These were rejected before as overlapping, because when seeking
        (C Int Int) one couldn't tell which to use.  But there's no problem when
        seeking (C Bool Int); it can only be the second.
      
        So instead of checking for overlap when adding a new instance declaration,
        we check for overlap when looking up an Inst.  If we find more than one
        matching instance, we see if any of the candidates dominates the others
        (in the sense of being a substitution instance of all the others);
        and only if not do we report an error.
      
      
      
      	------------------------
      	     Medium things
      	------------------------
      
      * The TcRn monad is generalised a bit further.  It's now based on utils/IOEnv.lhs,
        the IO monad with an environment.  The desugarer uses the monad too,
        so that anything it needs can get faulted in nicely.
      
      * Reduce the number of wired-in things; in particular Word and Integer
        are no longer wired in.  The latter required HsLit.HsInteger to get a
        Type argument.  The 'derivable type classes' data types (:+:, :*: etc)
        are not wired in any more either (see stuff about derivable type classes
        below).
      
      * The PersistentComilerState is now held in a mutable variable
        in the HscEnv.  Previously (a) it was passed to and then returned by
        many top-level functions, which was painful; (b) it was invariably
        accompanied by the HscEnv.  This change tidies up top-level plumbing
        without changing anything important.
      
      * Derivable type classes are treated much more like 'deriving' clauses.
        Previously, the Ids for the to/from functions lived inside the TyCon,
        but now the TyCon simply records their existence (with a simple boolean).
        Anyone who wants to use them must look them up in the environment.
      
        This in turn makes it easy to generate the to/from functions (done
        in types/Generics) using HsSyn (like TcGenDeriv for ordinary derivings)
        instead of CoreSyn, which in turn means that (a) we don't have to figure
        out all the type arguments etc; and (b) it'll be type-checked for us.
        Generally, the task of generating the code has become easier, which is
        good for Manuel, who wants to make it more sophisticated.
      
      * A Name now says what its "parent" is. For example, the parent of a data
        constructor is its type constructor; the parent of a class op is its
        class.  This relationship corresponds exactly to the Avail data type;
        there may be other places we can exploit it.  (I made the change so that
        version comparison in interface files would be a bit easier; but in
        fact it tided up other things here and there (see calls to
        Name.nameParent).  For example, the declaration pool, of declararations
        read from interface files, but not yet used, is now keyed only by the 'main'
        name of the declaration, not the subordinate names.
      
      * New types OccEnv and OccSet, with the usual operations.
        OccNames can be efficiently compared, because they have uniques, thanks
        to the hashing implementation of FastStrings.
      
      * The GlobalRdrEnv is now keyed by OccName rather than RdrName.  Not only
        does this halve the size of the env (because we don't need both qualified
        and unqualified versions in the env), but it's also more efficient because
        we can use a UniqFM instead of a FiniteMap.
      
        Consequential changes to Provenance, which has moved to RdrName.
      
      * External Core remains a bit of a hack, as it was before, done with a mixture
        of HsDecls (so that recursiveness and argument variance is still inferred),
        and IfaceExprs (for value declarations).  It's not thoroughly tested.
      
      
      	------------------------
      	     Minor things
      	------------------------
      
      * DataCon fields dcWorkId, dcWrapId combined into a single field
        dcIds, that is explicit about whether the data con is a newtype or not.
        MkId.mkDataConWorkId and mkDataConWrapId are similarly combined into
        MkId.mkDataConIds
      
      * Choosing the boxing strategy is done for *source* type decls only, and
        hence is now in TcTyDecls, not DataCon.
      
      * WiredIn names are distinguished by their n_sort field, not by their location,
        which was rather strange
      
      * Define Maybes.mapCatMaybes :: (a -> Maybe b) -> [a] -> [b]
        and use it here and there
      
      * Much better pretty-printing of interface files (--show-iface)
      
      Many, many other small things.
      
      
      	------------------------
      	     File changes
      	------------------------
      * New iface/ subdirectory
      * Much of RnEnv has moved to iface/IfaceEnv
      * MkIface and BinIface have moved from main/ to iface/
      * types/Variance has been absorbed into typecheck/TcTyDecls
      * RnHiFiles and RnIfaces have vanished entirely.  Their
        work is done by iface/LoadIface
      * hsSyn/HsCore has gone, replaced by iface/IfaceSyn
      * typecheck/TcIfaceSig has gone, replaced by iface/TcIface
      * typecheck/TcMonoType has been renamed to typecheck/TcHsType
      * basicTypes/Var.hi-boot and basicTypes/Generics.hi-boot have gone altogether
      98688c6e
  2. 23 Sep, 2003 1 commit
  3. 20 Jun, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-06-20 11:14:18 by simonpj] · 1f861358
      simonpj authored
      ------------------------------
      	Fix a small quantification bug
      	------------------------------
      
      We were quantifying over too few type variables, because fdPredsOfInsts was
      being too eager to discard predicates. This only affects rather obscure
      programs.  Here's the one Iavor found:
      
      	class C a b where f :: a -> b
      	g x = fst (f x)
      
      We want to get the type
         	g :: forall a b c.  C a (b,c) => a -> b
      but GHC 6.0 bogusly gets
         	g :: forall a b.  C a (b,()) => a -> b
      
      A test is in should_compile/tc168
      1f861358
  4. 16 Jun, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-06-16 15:32:16 by simonpj] · f5fbd41c
      simonpj authored
      --------------------------
      	Remove some wired-in types
      	--------------------------
      
      ptrTyCon, funPtrTyCon, addrTyCon, stablePtrTyCon have no business
      being wired in. This commit makes them into knownKey Names, which
      is much better.
      f5fbd41c
  5. 29 May, 2003 1 commit
    • sof's avatar
      [project @ 2003-05-29 14:39:26 by sof] · a7d8f437
      sof authored
      Support for interop'ing with .NET via FFI declarations along the
      lines of what Hugs98.NET offers, see
      
       http://haskell.org/pipermail/cvs-hugs/2003-March/001723.html
      
      for FFI decl details.
      
      To enable, configure with --enable-dotnet + have a look
      in ghc/rts/dotnet/Makefile for details of what tools are needed to
      build the .NET interop layer (tools from VS.NET / Framework SDK.)
      
      The commit doesn't include some library additions + wider-scale
      testing is required before this extension can be regarded as available
      for general use. 'foreign import dotnet' is currently only supported
      by the C backend.
      a7d8f437
  6. 16 Apr, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-04-16 13:34:13 by simonpj] · 221b6b69
      simonpj authored
      ----------------------------------
       Use the Infer/Check idea for typechecking higher-rank types
      	----------------------------------
      
      The main idea is that
      
      	data Expected ty = Infer (TcRef ty) | Check ty
      
      	tcMonoExpr :: Expr -> Expected TcRhoType -> TcM Expra
      
      
      This "Expected" type tells tcMonoExpr whether it's doing inference or
      checking.  It replaces the "HoleTv" flavour of type variable.
      
      This actually leads to slightly more lines of code, but it's much
      clearer, and the new type distinctions showed up several subtle bugs
      in the previous implementation.  It all arose out of writing the
      prototype implementation for the paper.
      
      Error messages wibble around a little bit.  I'm not quite certain why!  But the
      changes look like improvements to me.
      221b6b69
  7. 20 Feb, 2003 1 commit
  8. 12 Feb, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-02-12 15:01:31 by simonpj] · 42b63073
      simonpj authored
      -------------------------------------
        Big upheaval to the way that constructors are named
      	-------------------------------------
      
      This commit enshrines the new story for constructor names.  We could never
      really get External Core to work nicely before, but now it does.
      
      The story is laid out in detail in the Commentary
      	ghc/docs/comm/the-beast/data-types.html
      so I will not repeat it here.
      
      	[Manuel: the commentary isn't being updated, apparently.]
      
      However, the net effect is that in Core and in External Core, contructors look
      like constructors, and the way things are printed is all consistent.
      
      It is a fairly pervasive change (which is why it has been so long postponed),
      but I hope the question is now finally closed.
      
      All the libraries compile etc, and I've run many tests, but doubtless there will
      be some dark corners.
      42b63073
  9. 04 Feb, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-02-04 15:09:38 by simonpj] · 957bf375
      simonpj authored
      -------------------------------------
      	Remove all vestiges of usage analysis
      	-------------------------------------
      
      This commit removes a large blob of usage-analysis-related code, almost
      all of which was commented out.
      
      Sadly, it doesn't look as if Keith is going to have enough time to polish it
      up, and in any case the actual performance benefits (so far as we can measure
      them) turned out to be pretty modest (a few percent).
      
      So, with regret, I'm chopping it all out.  It's still there in the repository
      if anyone wants go hack on it.  And Tobias Gedell at Chalmers is implementing
      a different analysis, via External Core.
      957bf375
  10. 23 Jan, 2003 1 commit
    • simonmar's avatar
      [project @ 2003-01-23 16:01:33 by simonmar] · 6873f3d4
      simonmar authored
      Allow FFI declarations to have polymorphic types. eg:
      
      foreign import ccall unsafe "stdlib.h &free" pFree :: FunPtr (Ptr a -> IO ())
      
      (the change actually removed a line, the extra lines are because I
      reformatted an import declaration).
      6873f3d4
  11. 11 Nov, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-11-11 10:53:28 by simonpj] · 0adb7175
      simonpj authored
      ------------------
        	   Fix a newtype-deriving bug
      		------------------
      
      The new newtype-deriving mechanism was erroneously using the
      *representation type* of the newtype.  The rep type looks through all
      ihtermediate newtypes, so that is wrong.  See Note [newtype
      representation] in TcDeriv.lhs
      
      deriving/should_run/drvrun013 now tests for this.
      0adb7175
  12. 13 Sep, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-09-13 15:02:25 by simonpj] · 9af77fa4
      simonpj authored
      --------------------------------------
      	Make Template Haskell into the HEAD
      	--------------------------------------
      
      This massive commit transfers to the HEAD all the stuff that
      Simon and Tim have been doing on Template Haskell.  The
      meta-haskell-branch is no more!
      
      WARNING: make sure that you
      
        * Update your links if you are using link trees.
          Some modules have been added, some have gone away.
      
        * Do 'make clean' in all library trees.
          The interface file format has changed, and you can
          get strange panics (sadly) if GHC tries to read old interface files:
          e.g.  ghc-5.05: panic! (the `impossible' happened, GHC version 5.05):
      	  Binary.get(TyClDecl): ForeignType
      
        * You need to recompile the rts too; Linker.c has changed
      
      
      However the libraries are almost unaltered; just a tiny change in
      Base, and to the exports in Prelude.
      
      
      NOTE: so far as TH itself is concerned, expression splices work
      fine, but declaration splices are not complete.
      
      
      		---------------
      		The main change
      		---------------
      
      The main structural change: renaming and typechecking have to be
      interleaved, because we can't rename stuff after a declaration splice
      until after we've typechecked the stuff before (and the splice
      itself).
      
      * Combine the renamer and typecheker monads into one
      	(TcRnMonad, TcRnTypes)
        These two replace TcMonad and RnMonad
      
      * Give them a single 'driver' (TcRnDriver).  This driver
        replaces TcModule.lhs and Rename.lhs
      
      * The haskell-src library package has a module
      	Language/Haskell/THSyntax
        which defines the Haskell data type seen by the TH programmer.
      
      * New modules:
      	hsSyn/Convert.hs 	converts THSyntax -> HsSyn
      	deSugar/DsMeta.hs 	converts HsSyn -> THSyntax
      
      * New module typecheck/TcSplice type-checks Template Haskell splices.
      
      		-------------
      		Linking stuff
      		-------------
      
      * ByteCodeLink has been split into
      	ByteCodeLink	(which links)
      	ByteCodeAsm	(which assembles)
      
      * New module ghci/ObjLink is the object-code linker.
      
      * compMan/CmLink is removed entirely (was out of place)
        Ditto CmTypes (which was tiny)
      
      * Linker.c initialises the linker when it is first used (no need to call
        initLinker any more).  Template Haskell makes it harder to know when
        and whether to initialise the linker.
      
      
      	-------------------------------------
      	Gathering the LIE in the type checker
      	-------------------------------------
      
      * Instead of explicitly gathering constraints in the LIE
      	tcExpr :: RenamedExpr -> TcM (TypecheckedExpr, LIE)
        we now dump the constraints into a mutable varabiable carried
        by the monad, so we get
      	tcExpr :: RenamedExpr -> TcM TypecheckedExpr
      
        Much less clutter in the code, and more efficient too.
        (Originally suggested by Mark Shields.)
      
      
      		-----------------
      		Remove "SysNames"
      		-----------------
      
      Because the renamer and the type checker were entirely separate,
      we had to carry some rather tiresome implicit binders (or "SysNames")
      along inside some of the HsDecl data structures.  They were both
      tiresome and fragile.
      
      Now that the typechecker and renamer are more intimately coupled,
      we can eliminate SysNames (well, mostly... default methods still
      carry something similar).
      
      		-------------
      		Clean up HsPat
      		-------------
      
      One big clean up is this: instead of having two HsPat types (InPat and
      OutPat), they are now combined into one.  This is more consistent with
      the way that HsExpr etc is handled; there are some 'Out' constructors
      for the type checker output.
      
      So:
      	HsPat.InPat	--> HsPat.Pat
      	HsPat.OutPat	--> HsPat.Pat
      	No 'pat' type parameter in HsExpr, HsBinds, etc
      
      	Constructor patterns are nicer now: they use
      		HsPat.HsConDetails
      	for the three cases of constructor patterns:
      		prefix, infix, and record-bindings
      
      	The *same* data type HsConDetails is used in the type
      	declaration of the data type (HsDecls.TyData)
      
      Lots of associated clean-up operations here and there.  Less code.
      Everything is wonderful.
      9af77fa4
  13. 06 Sep, 2002 2 commits
  14. 29 Jul, 2002 1 commit
  15. 20 Jun, 2002 1 commit
  16. 22 Apr, 2002 1 commit
  17. 25 Mar, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-03-25 15:08:38 by simonpj] · aaed1181
      simonpj authored
      -------------------------------
      	Fix bugs in rank-N polymorphism
      	-------------------------------
      
      Discussion with Mark showed up some bugs in the rank-N
      polymorphism stuff, especally concerning the treatment of
      'hole' type variables.
      
      See especially TcMType:
      	newHoleTyVar
      	readHoleResult
      	zapToType
      
      Also the treatment of conditionals and case branches
      is done right now, using zapToType
      aaed1181
  18. 14 Mar, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-03-14 15:27:15 by simonpj] · 1553c778
      simonpj authored
      ------------------------
      	Change
      		GlobalName --> ExternalName
      		LocalName  ->  InternalName
      	------------------------
      
      For a long time there's been terminological confusion between
      
      	GlobalName vs LocalName	 (property of a Name)
      	GlobalId vs LocalId	 (property of an Id)
      
      I've now changed the terminology for Name to be
      
      	ExternalName vs InternalName
      
      I've also added quite a bit of documentation in the Commentary.
      1553c778
  19. 12 Mar, 2002 2 commits
    • simonpj's avatar
      [project @ 2002-03-12 15:55:26 by simonpj] · 72c2f581
      simonpj authored
      ------------------------
      	Fix a type-invariant bug
      	------------------------
      
      We need to call Type.mkGenTyConApp from Type.mkAppTy, in
      case there's a partially applied type synonym.  Explanation
      with Type.mkAppTy.  All part of GHC's rather liberal treatment
      of type synonyms.
      
      Shown up by a program from Ralf Laemmel:
      
      	type Generic i o = forall x. i x -> o x
      	type Id x = x
      	comb :: Generic Id Id
      
      Test is typecheck/should_compile/tc149.hs
      72c2f581
    • simonpj's avatar
      [project @ 2002-03-12 09:12:57 by simonpj] · 49c84dec
      simonpj authored
      Comments
      49c84dec
  20. 08 Mar, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-03-08 15:50:53 by simonpj] · a170160c
      simonpj authored
      --------------------------------------
      	Lift the class-method type restriction
      	--------------------------------------
      
      Haskell 98 prohibits class method types to mention constraints on the
      class type variable, thus:
      
        class Seq s a where
          fromList :: [a] -> s a
          elem     :: Eq a => a -> s a -> Bool
      
      The type of 'elem' is illegal in Haskell 98, because it contains the
      constraint 'Eq a', which constrains only the class type variable (in
      this case 'a').
      
      This commit lifts the restriction.  The way we do that is to do a full
      context reduction (tcSimplifyCheck) step for each method separately in
      TcClassDcl.tcMethodBind, rather than doing a single context reduction
      for the whole group of method bindings.
      
      As a result, I had to reorganise the code a bit, and tidy up.
      a170160c
  21. 28 Feb, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-02-28 12:17:19 by simonpj] · 469c3333
      simonpj authored
      ---------------------------------
      	Fix a rather obscure bug in tcGen
      	---------------------------------
      
      This bug concerns deciding when a type variable "escapes",
      and hence we can't generalise it.  Our new subsumption-checking
      machinery for higher-ranked types requires a slightly
      more general approach than I had before.  The main excitement
      is in TcUnify.checkSigTyVars and its friends.
      
      As usual, I moved functions around and cleaned things up a bit;
      hence the multi-module commit.
      469c3333
  22. 13 Feb, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-02-13 15:14:06 by simonpj] · e7030995
      simonpj authored
      --------------------------------------------
      	Fix a bugs in type inference for rank-N types
      	--------------------------------------------
      
      We discovered this bug when looking at type rules!
      
      1. When type checking (e :: sigma-ty), we must specialise sigma-ty,
         else we lose the invariant that tcMonoType has.
      
      2. In tcExpr_id, we should pass in a Hole tyvar not an ordinary tyvar.
      
      As usual, I moved some functions around in consequence.
      e7030995
  23. 07 Feb, 2002 2 commits
    • simonpj's avatar
      [project @ 2002-02-07 14:06:00 by simonpj] · ad552fe2
      simonpj authored
      -------------------------------------------
      	Improve the "stragely-kinded tyvar" problem
      	-------------------------------------------
      
      When the type checker finds a type variable with no binding,
      which means it can be instantiated with an arbitrary type, it
      usually instantiates it to Void.  Eg.
      
      	length []
      ===>
      	length Void (Nil Void)
      
      But in really obscure programs, the type variable might have
      a kind other than *, so we need to invent a suitably-kinded type.
      
      This commit uses
      	Void for kind *
      	List for kind *->*
      	Tuple for kind *->...*->*
      
      which deals with most cases.  (Previously, it only dealt with
      kind *.)
      
      In the other cases, it just makes up a TyCon with a suitable
      kind.  If this gets into an interface file, anyone reading that
      file won't understand it.  This is fixable (by making the client
      of the interface file make up a TyCon too) but it is tiresome and
      never happens, so I am leaving it.
      
      Most of the added lines are comments.
      ad552fe2
    • simonpj's avatar
      [project @ 2002-02-07 12:51:34 by simonpj] · 20f50b2a
      simonpj authored
      ----------------------------------------------------
      	Make TcType.match and TcUnify.uUnboundVar kind-aware
      	----------------------------------------------------
      
      George Russel had apparently-overlapping (ha) instance decls like
      
      	instance .. => C (a b) where
      	instance .. => C (x y) where
      
      But the a,b and x,y were different kinds!  Turned out that TcType.unify
      was kind-aware (so we didn't report a duplicate instance decl, but TcType.match
      was not (so we simply selected the wrong one, and got a mis-kinded constraint
      popping up from the ".."  part.  Very exciting to track down.
      
      I also make the ordinary unification kind-aware in the same way.  It's
      quite legitimate to attempt to unify, say,
      	(a b)    with     (c d)
      but the unification should fail if a's kind differs from c's.
      (There was a kind of debug warning before, but it's actually not an error
      in the compiler... so it should just make unification fail gracefully.)
      20f50b2a
  24. 06 Feb, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-02-06 15:54:23 by simonpj] · 979947f5
      simonpj authored
      Eliminate all vestiages of UsageTy, in preparation for
      	Keith's new version.  Hurrah!
      
      	Keith: LBVarInfo and usOnce,usMany are still there,
      	because I know you have eliminated LBVarInfo, and I didn't
      	want to cause unnecessary conflicts.
      979947f5
  25. 04 Feb, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-02-04 11:59:55 by simonpj] · 18dbe364
      simonpj authored
      -----------------------------
      	Improve type validity checking
      	-----------------------------
      
      Two main effects here
      
      a) Type synonyms can be unboxed tuples
      	tupe T = (# Int, Int #)
      
      	f :: Int -> T
      
      b) Hoisting works for implicit parameters
      
      	f :: Int -> (?x::Int) => Int
      18dbe364
  26. 21 Dec, 2001 1 commit
  27. 29 Nov, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-11-29 13:47:09 by simonpj] · 32a89583
      simonpj authored
      ------------------------------
      	Add linear implicit parameters
      	------------------------------
      
      Linear implicit parameters are an idea developed by Koen Claessen,
      Mark Shields, and Simon PJ, last week.  They address the long-standing
      problem that monads seem over-kill for certain sorts of problem, notably:
      
      	* distributing a supply of unique names
      	* distributing a suppply of random numbers
      	* distributing an oracle (as in QuickCheck)
      
      
      Linear implicit parameters are just like ordinary implicit parameters,
      except that they are "linear" -- that is, they cannot be copied, and
      must be explicitly "split" instead.  Linear implicit parameters are
      written '%x' instead of '?x'.  (The '/' in the '%' suggests the
      split!)
      
      For example:
      
          data NameSupply = ...
      
          splitNS :: NameSupply -> (NameSupply, NameSupply)
          newName :: NameSupply -> Name
      
          instance PrelSplit.Splittable NameSupply where
      	split = splitNS
      
      
          f :: (%ns :: NameSupply) => Env -> Expr -> Expr
          f env (Lam x e) = Lam x' (f env e)
      		    where
      		      x'   = newName %ns
      		      env' = extend env x x'
          ...more equations for f...
      
      Notice that the implicit parameter %ns is consumed
      	once by the call to newName
      	once by the recursive call to f
      
      So the translation done by the type checker makes
      the parameter explicit:
      
          f :: NameSupply -> Env -> Expr -> Expr
          f ns env (Lam x e) = Lam x' (f ns1 env e)
      		       where
      	 		 (ns1,ns2) = splitNS ns
      			 x' = newName ns2
      			 env = extend env x x'
      
      Notice the call to 'split' introduced by the type checker.
      How did it know to use 'splitNS'?  Because what it really did
      was to introduce a call to the overloaded function 'split',
      ndefined by
      
      	class Splittable a where
      	  split :: a -> (a,a)
      
      The instance for Splittable NameSupply tells GHC how to implement
      split for name supplies.  But we can simply write
      
      	g x = (x, %ns, %ns)
      
      and GHC will infer
      
      	g :: (Splittable a, %ns :: a) => b -> (b,a,a)
      
      The Splittable class is built into GHC.  It's defined in PrelSplit,
      and exported by GlaExts.
      
      Other points:
      
      * '?x' and '%x' are entirely distinct implicit parameters: you
        can use them together and they won't intefere with each other.
      
      * You can bind linear implicit parameters in 'with' clauses.
      
      * You cannot have implicit parameters (whether linear or not)
        in the context of a class or instance declaration.
      
      
      Warnings
      ~~~~~~~~
      The monomorphism restriction is even more important than usual.
      Consider the example above:
      
          f :: (%ns :: NameSupply) => Env -> Expr -> Expr
          f env (Lam x e) = Lam x' (f env e)
      		    where
      		      x'   = newName %ns
      		      env' = extend env x x'
      
      If we replaced the two occurrences of x' by (newName %ns), which is
      usually a harmless thing to do, we get:
      
          f :: (%ns :: NameSupply) => Env -> Expr -> Expr
          f env (Lam x e) = Lam (newName %ns) (f env e)
      		    where
      		      env' = extend env x (newName %ns)
      
      But now the name supply is consumed in *three* places
      (the two calls to newName,and the recursive call to f), so
      the result is utterly different.  Urk!  We don't even have
      the beta rule.
      
      Well, this is an experimental change.  With implicit
      parameters we have already lost beta reduction anyway, and
      (as John Launchbury puts it) we can't sensibly reason about
      Haskell programs without knowing their typing.
      
      Of course, none of this is throughly tested, either.
      32a89583
  28. 26 Nov, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-11-26 09:20:25 by simonpj] · 5e3f005d
      simonpj authored
      ----------------------
      	Implement Rank-N types
      	----------------------
      
      This commit implements the full glory of Rank-N types, using
      the Odersky/Laufer approach described in their paper
      	"Putting type annotations to work"
      
      In fact, I've had to adapt their approach to deal with the
      full glory of Haskell (including pattern matching, and the
      scoped-type-variable extension).  However, the result is:
      
      * There is no restriction to rank-2 types.  You can nest forall's
        as deep as you like in a type.  For example, you can write a type
        like
      	p :: ((forall a. Eq a => a->a) -> Int) -> Int
        This is a rank-3 type, illegal in GHC 5.02
      
      * When matching types, GHC uses the cunning Odersky/Laufer coercion
        rules.  For example, suppose we have
      	q :: (forall c. Ord c => c->c) -> Int
        Then, is this well typed?
      	x :: Int
      	x = p q
        Yes, it is, but GHC has to generate the right coercion.  Here's
        what it looks like with all the big lambdas and dictionaries put in:
      
      	x = p (\ f :: (forall a. Eq a => a->a) ->
      		 q (/\c \d::Ord c -> f c (eqFromOrd d)))
      
        where eqFromOrd selects the Eq superclass dictionary from the Ord
        dicationary:		eqFromOrd :: Ord a -> Eq a
      
      
      * You can use polymorphic types in pattern type signatures.  For
        example:
      
      	f (g :: forall a. a->a) = (g 'c', g True)
      
        (Previously, pattern type signatures had to be monotypes.)
      
      * The basic rule for using rank-N types is that you must specify
        a type signature for every binder that you want to have a type
        scheme (as opposed to a plain monotype) as its type.
      
        However, you don't need to give the type signature on the
        binder (as I did above in the defn for f).  You can give it
        in a separate type signature, thus:
      
      	f :: (forall a. a->a) -> (Char,Bool)
      	f g = (g 'c', g True)
      
        GHC will push the external type signature inwards, and use
        that information to decorate the binders as it comes across them.
        I don't have a *precise* specification of this process, but I
        think it is obvious enough in practice.
      
      * In a type synonym you can use rank-N types too.  For example,
        you can write
      
      	type IdFun = forall a. a->a
      
      	f :: IdFun -> (Char,Bool)
      	f g = (g 'c', g True)
      
        As always, type synonyms must always occur saturated; GHC
        expands them before it does anything else.  (Still, GHC goes
        to some trouble to keep them unexpanded in error message.)
      
      
      The main plan is as before.  The main typechecker for expressions,
      tcExpr, takes an "expected type" as its argument.  This greatly
      improves error messages.  The new feature is that when this
      "expected type" (going down) meets an "actual type" (coming up)
      we use the new subsumption function
      	TcUnify.tcSub
      which checks that the actual type can be coerced into the
      expected type (and produces a coercion function to demonstrate).
      
      The main new chunk of code is TcUnify.tcSub.  The unifier itself
      is unchanged, but it has moved from TcMType into TcUnify.  Also
      checkSigTyVars has moved from TcMonoType into TcUnify.
      Result: the new module, TcUnify, contains all stuff relevant
      to subsumption and unification.
      
      Unfortunately, there is now an inevitable loop between TcUnify
      and TcSimplify, but that's just too bad (a simple TcUnify.hi-boot
      file).
      
      
      All of this doesn't come entirely for free.  Here's the typechecker
      line count (INCLUDING comments)
      	Before	16,551
      	After	17,116
      5e3f005d
  29. 31 Oct, 2001 2 commits
    • simonpj's avatar
      [project @ 2001-10-31 16:17:59 by simonpj] · 317a1fd9
      simonpj authored
      Add hi-boot files for the new knot
      317a1fd9
    • simonpj's avatar
      [project @ 2001-10-31 15:22:53 by simonpj] · 61bfd5dd
      simonpj authored
      ------------------------------------------
      	Improved handling of scoped type variables
      	------------------------------------------
      
      The main effect of this commit is to allow scoped type variables
      in pattern bindings, thus
      
      	(x::a, y::b) = e
      
      This was illegal, but now it's ok.  a and b have the same scope
      as x and y.
      
      
      On the way I beefed up the info inside a type variable
      (TcType.TyVarDetails; c.f. IdInfo.GlobalIdDetails) which
      helps to improve error messages. Hence the wide ranging changes.
      Pity about the extra loop from Var to TcType, but can't be helped.
      61bfd5dd
  30. 25 Oct, 2001 2 commits
    • simonpj's avatar
      [project @ 2001-10-25 14:30:43 by simonpj] · d5f94cc1
      simonpj authored
      -------------------------------------------------------
        Correct an error in the handling of implicit parameters
        -------------------------------------------------------
      
      	MERGE WITH STABLE BRANCH UNLESS HARD TO DO
      
      Mark Shields discovered a bug in the way that implicit parameters
      are dealt with by the type checker.  It's all a bit subtle, and
      is extensively documented in TcSimplify.lhs.
      
      This commit makes the code both simpler and more correct.  It subtly
      changes the way in which type signatures are treated, but not in a way
      anyone would notice: see notes with "Question 2: type signatures"
      in TcSimplify.lhs.
      d5f94cc1
    • sof's avatar
      [project @ 2001-10-25 02:13:10 by sof] · 9e933350
      sof authored
      - Pet peeve removal / code tidyup, replaced various sub-optimal
        uses of 'length' with something a bit better, i.e., replaced
        the following patterns
      
         *  length as `cmpOp` length bs
         *  length as `cmpOp` val   -- incl. uses where val == 1 and val == 0
         *  {take,drop,splitAt} (length as) bs
         *  length [ () | pat <- as ]
      
        with uses of misc Util functions.
      
        I'd be surprised if there's a noticeable reduction in running
        times as a result of these changes, but every little bit helps.
      
        [ The changes have been tested wrt testsuite/ - I'm seeing a couple
          of unexpected breakages coming from CorePrep, but I'm currently
          assuming that these are due to other recent changes. ]
      
      - compMan/CompManager.lhs: restored 4.08 compilability + some code
        cleanup.
      
      None of these changes are HEADworthy.
      9e933350
  31. 26 Sep, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-09-26 15:12:33 by simonpj] · e0d750be
      simonpj authored
      ------------------
      		Simon's big commit
      		------------------
      
      This commit, which I don't think I can sensibly do piecemeal, consists
      of the things I've been doing recently, mainly directed at making
      Manuel, George, and Marcin happier with RULES.
      
      
      Reogranise the simplifier
      ~~~~~~~~~~~~~~~~~~~~~~~~~
      1. The simplifier's environment is now an explicit parameter.  This
      makes it a bit easier to figure out where it is going.
      
      2. Constructor arguments can now be arbitrary expressions, except
      when the application is the RHS of a let(rec).  This makes it much
      easier to match rules like
      
      	RULES
      	    "foo"  f (h x, g y) = f' x y
      
      In the simplifier, it's Simplify.mkAtomicArgs that ANF-ises a
      constructor application where necessary.  In the occurrence analyser,
      there's a new piece of context info (OccEncl) to say whether a
      constructor app is in a place where it should be in ANF.  (Unless
      it knows this it'll give occurrence info which will inline the
      argument back into the constructor app.)
      
      3. I'm experimenting with doing the "float-past big lambda" transformation
      in the full laziness pass, rather than mixed in with the simplifier (was
      tryRhsTyLam).
      
      4.  Arrange that
      	case (coerce (S,T) (x,y)) of ...
      will simplify.  Previous it didn't.
      A local change to CoreUtils.exprIsConApp_maybe.
      
      5. Do a better job in CoreUtils.exprEtaExpandArity when there's an
      error function in one branch.
      
      
      Phase numbers, RULES, and INLINE pragmas
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      1.  Phase numbers decrease from N towards zero (instead of increasing).
      This makes it easier to add new earlier phases, which is what users want
      to do.
      
      2.  RULES get their own phase number, N, and are disabled in phases before N.
      
      e.g. 	{-# RULES "foo" [2] forall x y.  f (x,y) = f' x y #-}
      
      Note the [2], which says "only active in phase 2 and later".
      
      3.  INLINE and NOINLINE pragmas have a phase number to.  This is now treated
      in just the same way as the phase number on RULE; that is, the Id is not inlined
      in phases earlier than N.  In phase N and later the Id *may* be inlined, and
      here is where INLINE and NOINLINE differ: INLNE makes the RHS look small, so
      as soon as it *may* be inlined it probably *will* be inlined.
      
      The syntax of the phase number on an INLINE/NOINLINE pragma has changed to be
      like the RULES case (i.e. in square brackets).  This should also make sure
      you examine all such phase numbers; many will need to change now the numbering
      is reversed.
      
      Inlining Ids is no longer affected at all by whether the Id appears on the
      LHS of a rule.  Now it's up to the programmer to put a suitable INLINE/NOINLINE
      pragma to stop it being inlined too early.
      
      
      Implementation notes:
      
      *  A new data type, BasicTypes.Activation says when a rule or inline pragma
      is active.   Functions isAlwaysActive, isNeverActive, isActive, do the
      obvious thing (all in BasicTypes).
      
      * Slight change in the SimplifierSwitch data type, which led to a lot of
      simplifier-specific code moving from CmdLineOpts to SimplMonad; a Good Thing.
      
      * The InlinePragma in the IdInfo of an Id is now simply an Activation saying
      when the Id can be inlined.  (It used to be a rather bizarre pair of a
      Bool and a (Maybe Phase), so this is much much easier to understand.)
      
      * The simplifier has a "mode" environment switch, replacing the old
      black list.  Unfortunately the data type decl has to be in
      CmdLineOpts, because it's an argument to the CoreDoSimplify switch
      
          data SimplifierMode = SimplGently | SimplPhase Int
      
      Here "gently" means "no rules, no inlining".   All the crucial
      inlining decisions are now collected together in SimplMonad
      (preInlineUnconditionally, postInlineUnconditionally, activeInline,
      activeRule).
      
      
      Specialisation
      ~~~~~~~~~~~~~~
      1.  Only dictionary *functions* are made INLINE, not dictionaries that
      have no parameters.  (This inline-dictionary-function thing is Marcin's
      idea and I'm still not sure whether it's a good idea.  But it's definitely
      a Bad Idea when there are no arguments.)
      
      2.  Be prepared to specialise an INLINE function: an easy fix in
      Specialise.lhs
      
      But there is still a problem, which is that the INLINE wins
      at the call site, so we don't use the specialised version anyway.
      I'm still unsure whether it makes sense to SPECIALISE something
      you want to INLINE.
      
      
      
      
      
      Random smaller things
      ~~~~~~~~~~~~~~~~~~~~~~
      
      * builtinRules (there was only one, but may be more) in PrelRules are now
        incorporated.   They were being ignored before...
      
      * OrdList.foldOL -->  OrdList.foldrOL, OrdList.foldlOL
      
      * Some tidying up of the tidyOpenTyVar, tidyTyVar functions.  I've
        forgotten exactly what!
      e0d750be
  32. 07 Sep, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-09-07 12:34:03 by simonpj] · b8711eeb
      simonpj authored
      -------------------
      	Newtypes and ccalls
      	     [addendum]
      	-------------------
      
      	MERGE WITH STABLE BRANCH
      
      I accidentally omitted these two wibbles from my previous commit.
      I've added PrelNames.unitTyConKey, and used it in TcType and DsCCall.
      b8711eeb
  33. 06 Sep, 2001 1 commit
  34. 28 Aug, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-08-28 10:06:29 by simonpj] · b0604aad
      simonpj authored
      ----------------------------------------
      	Make isFFIArgumentTy understand newtypes
      	----------------------------------------
      
      This fixes the bug Manuel reported:
      
      	newtype T = T (Ptr T)
      	foreign import ccall foo :: T -> IO (Ptr T)
      
        test.hs:6:
            Unacceptable argument type in foreign declaration: T
      
      
      On the way, I moved isFFIArgumentTy and friends out of TysWiredIn,
      where they didn't really belong, into TcType.  That in turn force
      me to move isStrictType, and isPrimitiveType.
      b0604aad
  35. 14 Aug, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-08-14 06:35:56 by simonpj] · 2767767f
      simonpj authored
      1. Arrange that w/w records unfoldings
         And that the simplifier preserves them
      
      2. Greatly improve structure of checking user types in the typechecker
         Main changes:
      	TcMType.checkValidType checks for a valid type
      	TcMonoType.tcHsSigType uses checkValidType
      	Type and class decls use TcMonoType.tcHsType (which does not
      		check for validity) inside the knot in TcTyClsDecls,
      		and then runs TcTyDecls.checkValidTyCon
      		or TcClassDcl.checkValidClass to check for validity
      		once the knot is tied
      2767767f