1. 21 Oct, 2003 3 commits
  2. 10 Oct, 2003 1 commit
  3. 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
  4. 16 Sep, 2003 1 commit
    • simonmar's avatar
      [project @ 2003-09-16 13:03:37 by simonmar] · 2129fa6f
      simonmar authored
      Legacy Removal
      ~~~~~~~~~~~~~~
      
      The following features have been consigned to the bit bucket:
      
        _ccall_
        _casm_
        ``....''  (lit-lits)
        the CCallable class
        the CReturnable class
      2129fa6f
  5. 27 Jun, 2003 1 commit
  6. 24 Jun, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-06-24 07:58:18 by simonpj] · 16e4ce4c
      simonpj authored
      ----------------------------------------------
      	Add support for Ross Paterson's arrow notation
      	----------------------------------------------
      
      Ross Paterson's ICFP'01 paper described syntax to support John Hughes's
      "arrows", rather as do-notation supports monads.  Except that do-notation is
      relatively modest -- you can write monads by hand without much trouble --
      whereas arrow-notation is more-or-less essential for writing arrow programs.
      It desugars to a massive pile of tuple construction and selection!
      
      For some time, Ross has had a pre-processor for arrow notation, but the
      resulting type error messages (reported in terms of the desugared code)
      are impenetrable.  This commit integrates the syntax into GHC.  The
      type error messages almost certainly still require tuning, but they should
      be better than with the pre-processor.
      
      Main syntactic changes (enabled with -farrows)
      
         exp ::= ... | proc pat -> cmd
      
         cmd ::= exp1 -<  exp2   |  exp1 >-  exp2
      	|  exp1 -<< exp2   |  exp1 >>- exp2
      	| \ pat1 .. patn -> cmd
      	| let decls in cmd
      	| if exp then cmd1 else cmd2
      	| do { cstmt1 .. cstmtn ; cmd }
      	| (| exp |) cmd1 .. cmdn
      	| cmd1 qop cmd2
      	| case exp of { calts }
      
         cstmt :: = let decls
      	 |   pat <- cmd
      	 |   rec { cstmt1 .. cstmtn }
      	 |   cmd
      
      New keywords and symbols:
      	proc rec
      	-<   >-   -<<   >>-
      	(|  |)
      
      The do-notation in cmds was not described in Ross's ICFP'01 paper; instead
      it's in his chapter in The Fun of Programming (Plagrave 2003).
      
      The four arrow-tail forms (-<) etc cover
        (a) which order the pices come in (-<  vs  >-), and
        (b) whether the locally bound variables can be used in the
      		arrow part (-<  vs  -<<) .
      In previous presentations, the higher-order-ness (b) was inferred,
      but it makes a big difference to the typing required so it seems more
      consistent to be explicit.
      
      The 'rec' form is also available in do-notation:
        * you can use 'rec' in an ordinary do, with the obvious meaning
        * using 'mdo' just says "infer the minimal recs"
      
      
      Still to do
      ~~~~~~~~~~~
      Top priority is the user manual.
      
      The implementation still lacks an implementation of
      the case form of cmd.
      
      
      Implementation notes
      ~~~~~~~~~~~~~~~~~~~~
      Cmds are parsed, and indeed renamed, as expressions.  The type checker
      distinguishes the two.
      16e4ce4c
  7. 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
  8. 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
  9. 10 Apr, 2003 1 commit
  10. 27 Mar, 2003 1 commit
  11. 26 Feb, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-02-26 17:04:11 by simonpj] · c86e9006
      simonpj authored
      ----------------------------------
      	Improve higher-rank type inference
      	----------------------------------
      
      Yanling Wang pointed out that if we have
      
      	f = \ (x :: forall a. a->a). x
      
      it would be reasonable to expect that type inference would get the "right"
      rank-2 type for f.  She also found that the plausible definition
      
      	f :: (forall a. a->a) = \x -> x
      
      acutally failed to type check.
      
      This commit fixes up TcBinds.tcMonoBinds so that it does a better job.
      The main idea is that there are three cases to consider in a function binding:
      
        a) 'f' has a separate type signature
      	In this case, we know f's type everywhere
      
        b) The binding is recursive, and there is no type sig
      	In this case we must give f a monotype in its RHS
      
        c) The binding is non-recursive, and there is no type sig
      	Then we do not need to add 'f' to the envt, and can
      	simply infer a type for the RHS, which may be higher
      	ranked.
      c86e9006
  12. 21 Feb, 2003 2 commits
    • simonpj's avatar
      [project @ 2003-02-21 13:27:53 by simonpj] · 84ed91ab
      simonpj authored
      -------------------------------------
      	Improve the "unused binding" warnings
      	-------------------------------------
      
      We've had a succession of hacks for reporting warnings for
      unused bindings.  Consider
      
      	module M( f ) where
      
       	f x = x
      
      	g x = g x + h x
      	h x = x
      
      Here, g mentions itself and h, but is not itself mentioned. So
      really both g and h are dead code.  We've been getting this wrong
      for ages, and every hack so far has failed on some simple programs.
      
      This commit does a much better job.  The renamer applied to a bunch
      of bindings returns a NameSet.DefUses, which is a dependency-ordered
      lists of def/use pairs.  It's documented in NameSet.
      Given this, we can work out precisely what is not used, in a nice
      tidy way.
      
      It's less convenient in the case of type and class declarations, because
      the strongly-connected-component analysis can span module boundaries.
      So things are pretty much as they were for these.
      
      
      As usual, there was a lot of chuffing around tidying things up.
      I havn't tested it at all thoroughly yet.
      
      Various unrelated import-decl-pruning has been done too.
      84ed91ab
    • simonpj's avatar
      [project @ 2003-02-21 12:16:44 by simonpj] · 802b299f
      simonpj authored
      Debugging hook jiggling
      802b299f
  13. 04 Feb, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-02-04 12:28:22 by simonpj] · 115f0fae
      simonpj authored
      ---------------------------------------------------
      	Important fix to the handling of class methods that
      	      mention their own class type variable
      	---------------------------------------------------
      
      [NB: I'm not 100% certain that this commit is independent of the
           Template-Haskell-related commit I'm doing at the same time.
           I've tried to separate them but may not have succeeded totally.]
      
      This bug gives utterly bogus (detected by Core Lint) programs.
      Isaac Jones discovered it.  Here's an example, now enshrined as tc165.
      
          class C a where
      	f :: (Eq a) => a
      
          instance C () where
      	f = f
      
      The instance decl was translated as
      
          dfC() = MkC (let f = \dEq -> f in f)
      
      which is utterly wrong.  Reason: the 'f' on the left was being treated
      as an available Inst, but it doesn't obey INVARIANT 2 for Insts, which
      is that they are applied to all their dictionaries.  (See the data type
      decl for Inst.)
      
      Solution: don't include such class methods in the available Insts.
      115f0fae
  14. 13 Jan, 2003 2 commits
  15. 28 Nov, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-11-28 17:17:41 by simonpj] · 3c58c25b
      simonpj authored
      -------------------------------
            A day's work to improve error messages
      	-------------------------------
      
      1.  Indicate when the cause of the error is likely to be the monomorpism
          restriction, and identify the offending variables.  This involves
          mainly tcSimplifyTop and its error generation.
      
      2.  Produce much better kind error messages.  No more
            ../alonzo/DiGraph.hs:40:
      	  Couldn't match `* -> *' against `Type bx'
      	      Expected kind: * -> *
      	      Inferred kind: Type bx
      	  When checking that `DiGraph n' is a type
      
      It took a surprisingly long time to get the details right.
      3c58c25b
  16. 19 Nov, 2002 1 commit
  17. 18 Nov, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-11-18 14:25:50 by simonpj] · 4e84be0c
      simonpj authored
      ----------------------------------------
      	Class ops that do not introduce for-alls
      	----------------------------------------
      
      	MERGE TO STABLE (if poss)
      
      The handling of class ops that do not add an extra for-all
      was utterly bogus.  For example:
      
      	class C a where
      	    fc :: (?p :: String) => a;
      
      	class D a where
      	    fd :: (Ord a) => [a] -> [a]
      
      De-bogus-ing means
      
      a) Being careful when taking apart the class op type in
      	MkIface.tcClassOpSig
      
      b) Ditto when making the method Id in an instance binding.
         Hence new function Inst.tcInstClassOp, and its calls
         in TcInstDcls, and TcClassDcls
      4e84be0c
  18. 18 Oct, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-10-18 13:41:50 by simonpj] · f53483a2
      simonpj authored
      --------------------------------
         Fix a serious error in the "newtype deriving" feature
      	--------------------------------
      
      The "newtype deriving" feature lets you derive arbitrary classes for
      a newtype, not just the built-in ones (Read, Show, Ix etc).  It's very
      cool, but Hal Duame discovered that it did utterly the Wrong Thing
      for superclasses.  E.g.
      
      	newtype Foo = MkFoo Int deriving( Show, Num, Eq )
      
      You'd get a Num instance for Foo that was *identical* to the
      Num instance for Int, *including* the Show superclass. So the
      superclass in the Num dictionary would show a Foo just like an
      Int, which is wrong... it should show as "Foo n".
      
      This commit fixes the problem, by building a new dictionary every time,
      but using the methods from the dictionary for the representation type.
      
      I also fixed a bug that prevented it working altogether when the
      representation type was not the application of a type constructor.
      For example, this now works
      
      	newtype Foo a = MkFoo a deriving( Num, Eq, Show )
      
      
      I also made it a bit more efficient in the case where the type is
      not parameterised.  Then the "dfun" doesn't need to be a function.
      f53483a2
  19. 09 Oct, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-10-09 15:03:48 by simonpj] · 8c1b6bd7
      simonpj authored
      -----------------------------------
      	Lots more Template Haskell stuff
      	-----------------------------------
      
      At last!  Top-level declaration splices work!
      Syntax is
      
      	$(f x)
      
      not "splice (f x)" as in the paper.
      
      Lots jiggling around, particularly with the top-level plumbining.
      Note the new data type HsDecls.HsGroup.
      8c1b6bd7
  20. 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
  21. 29 Jul, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-07-29 12:22:37 by simonpj] · 2ddea0a8
      simonpj authored
      *** MERGE TO STABLE BRANCH ***
      
      
      Surprisingly large delta to make rebindable names work properly.
      I was sloppily not checking the type of the user-supplied name,
      and Ashley Yakeley's first experiment showed up the problem!
      
      Solution: typechecker has to check both the 'standard' name and
      the 'user' name and check the latter has a type compatible with the
      former.
      
      The main comment is with Inst.tcSyntaxName (a new function).
      2ddea0a8
  22. 23 Jul, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-07-23 14:58:16 by simonpj] · e0a56725
      simonpj authored
      Use tcLookupId, not tcLookupGlobalId, in Inst.newMethodFromName
      
          This really only affects the behaviour with -fno-implicit-prelude
      
      	*** MERGE TO STABLE BRANCH ***
      e0a56725
  23. 11 Apr, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-04-11 12:03:29 by simonpj] · a7b95beb
      simonpj authored
      -------------------
      	Mainly derived Read
      	-------------------
      
      This commit is a tangle of several things that somehow got wound up
      together, I'm afraid.
      
      
      The main course
      ~~~~~~~~~~~~~~~
      Replace the derived-Read machinery with Koen's cunning new parser
      combinator library.   The result should be
      	* much smaller code sizes from derived Read
      	* faster execution of derived Read
      
      WARNING: I have not thoroughly tested this stuff; I'd be glad if you did!
      	 All the hard work is done, but there may be a few nits.
      
      The Read class gets two new methods, not exposed
      in the H98 inteface of course:
        class Read a where
          readsPrec    :: Int -> ReadS a
          readList     :: ReadS [a]
          readPrec     :: ReadPrec a		-- NEW
          readListPrec :: ReadPrec [a]	-- NEW
      
      There are the following new libraries:
      
        Text.ParserCombinators.ReadP		Koens combinator parser
        Text.ParserCombinators.ReadPrec	Ditto, but with precedences
      
        Text.Read.Lex				An emasculated lexical analyser
      					that provides the functionality
      					of H98 'lex'
      
      TcGenDeriv is changed to generate code that uses the new libraries.
      The built-in instances of Read (List, Maybe, tuples, etc) use the new
      libraries.
      
      
      Other stuff
      ~~~~~~~~~~~
      1. Some fixes the the plumbing of external-core generation. Sigbjorn
      did most of the work earlier, but this commit completes the renaming and
      typechecking plumbing.
      
      2. Runtime error-generation functions, such as GHC.Err.recSelErr,
      GHC.Err.recUpdErr, etc, now take an Addr#, pointing to a UTF8-encoded
      C string, instead of a Haskell string.  This makes the *calls* to these
      functions easier to generate, and smaller too, which is a good thing.
      
      In particular, it means that MkId.mkRecordSelectorId doesn't need to
      be passed "unpackCStringId", which was GRUESOME; and that in turn means
      that tcTypeAndClassDecls doesn't need to be passed unf_env, which is
      a very worthwhile cleanup.   Win/win situation.
      
      3.  GHC now faithfully translates do-notation using ">>" for statements
      with no binding, just as the report says.  While I was there I tidied
      up HsDo to take a list of Ids instead of 3 (but now 4) separate Ids.
      Saves a bit of code here and there.  Also introduced Inst.newMethodFromName
      to package a common idiom.
      a7b95beb
  24. 03 Apr, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-04-03 09:45:14 by simonpj] · f2f40c0f
      simonpj authored
      -----------------------------
      	Put existential tyvars second
      	[fixes ParsecPerm lint error]
      	-----------------------------
      
      In an existential data constr:
      
      	data Eq a => T a = forall b. Ord b => MkT a [b]
      
      the type of MkT is
      
      	MkT :: forall a b . Ord b => a -> [b] -> MkT a
      
      Note that the existential tyvars (b in this case) come *after*
      the "ordinary" tyvars.
      
      I had switched this around earlier in the week, but I'm putting
      it back (and fixing a bug) because I found it really works better second.
      
      Reason: in a case expression we may find:
      	case (e :: T t) of { MkT b (d:Ord b) (x:t) (xs:[b]) -> ... }
      It's convenient to apply the rep-type of MkT to 't', to get
      	forall b. Ord b => ...
      and use that to check the pattern.  Mind you, this is really only
      use in CoreLint.
      f2f40c0f
  25. 01 Apr, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-04-01 08:23:30 by simonpj] · 9003a18c
      simonpj authored
      ------------------------------------
      	Change the treatment of the stupid
      	   context on data constructors
      	-----------------------------------
      
      Data types can have a context:
      
      	data (Eq a, Ord b) => T a b = T1 a b | T2 a
      
      and that makes the constructors have a context too
      (notice that T2's context is "thinned"):
      
      	T1 :: (Eq a, Ord b) => a -> b -> T a b
      	T2 :: (Eq a) => a -> T a b
      
      Furthermore, this context pops up when pattern matching
      (though GHC hasn't implemented this, but it is in H98, and
      I've fixed GHC so that it now does):
      
      	f (T2 x) = x
      gets inferred type
      	f :: Eq a => T a b -> a
      
      I say the context is "stupid" because the dictionaries passed
      are immediately discarded -- they do nothing and have no benefit.
      It's a flaw in the language.
      
      Up to now I have put this stupid context into the type of
      the "wrapper" constructors functions, T1 and T2, but that turned
      out to be jolly inconvenient for generics, and record update, and
      other functions that build values of type T (because they don't
      have suitable dictionaries available).
      
      So now I've taken the stupid context out.  I simply deal with
      it separately in the type checker on occurrences of a constructor,
      either in an expression or in a pattern.
      
      To this end
      
      * Lots of changes in DataCon, MkId
      
      * New function Inst.tcInstDataCon to instantiate a data constructor
      
      
      
      I also took the opportunity to
      
      * Rename
      	dataConId --> dataConWorkId
        for consistency.
      
      * Tidied up MkId.rebuildConArgs quite a bit, and renamed it
      	mkReboxingAlt
      
      * Add function DataCon.dataConExistentialTyVars, with the obvious meaning
      9003a18c
  26. 28 Mar, 2002 1 commit
  27. 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
  28. 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
  29. 04 Mar, 2002 1 commit
    • simonmar's avatar
      [project @ 2002-03-04 17:01:26 by simonmar] · 0171936c
      simonmar authored
      Binary Interface Files - stage 1
      --------------------------------
      
      This commit changes the default interface file format from text to
      binary, in order to improve compilation performace.
      
      To view an interface file, use 'ghc --show-iface Foo.hi'.
      
      utils/Binary.hs is the basic Binary I/O library, based on the nhc98
      binary I/O library but much stripped-down and working in terms of
      bytes rather than bits, and with some special features for GHC: it
      remembers which Module is being emitted to avoid dumping too many
      qualified names, and it keeps track of a "dictionary" of FastStrings
      so that we don't dump the same FastString more than once into the
      binary file.  I'll make a generic version of this for the libraries at
      some point.
      
      main/BinIface.hs contains most of the Binary instances.  Some
      instances are in the same module as the data type (RdrName, Name,
      OccName in particular).  Most instances were generated using a
      modified version of DrIFT, which I'll commit later.  However, editing
      them by hand isn't hard (certainly easier than modifying
      ParseIface.y).
      
      The first thing in a binary interface is the interface version, so
      nice error messages will be generated if the binary format changes and
      you still have old interfaces lying around.  The version also now
      includes the "way" as an extra sanity check.
      
      Other changes
      -------------
      
      I don't like the way FastStrings contain both hashed strings (with
      O(1) comparison) and literal C strings (with O(n) comparison).  So as
      a first step to separating these I made serveral "literal" type
      strings into hashed strings.  SLIT() still generates a literal, and
      now FSLIT() generates a hashed string.  With DEBUG on, you'll get a
      warning if you try to compare any SLIT()s with anything, and the
      compiler will fall over if you try to dump any literal C strings into
      an interface file (usually indicating a use of SLIT() which should be
      FSLIT()).
      
      mkSysLocal no longer re-encodes its FastString argument each time it
      is called.
      
      I also fixed the -pgm options so that the argument can now optionally
      be separted from the option.
      
      Bugfix: PrelNames declared Names for several comparison primops, eg.
      eqCharName, eqIntName etc. but these had different uniques from the
      real primop names.  I've moved these to PrimOps and defined them using
      mkPrimOpIdName instead, and deleted some for which we don't have real
      primops (Manuel: please check that things still work for you after
      this change).
      0171936c
  30. 14 Feb, 2002 1 commit
  31. 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
  32. 07 Feb, 2002 1 commit
  33. 28 Dec, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-12-28 17:25:31 by simonpj] · ae969b47
      simonpj authored
      ---------------------
      	Dealing with deriving
      	---------------------
      
      I spent a ridiculously long time peering at a bug report whereby
      a 'deriving' clause sent GHC 5.02.1 into a loop.  It was all to
      do with allowing instances like
      
      	instance Foo a b => Baz (T a)
      
      (Notice the 'b' on the left which does not appear on the right.)
      
      I realised that it's hard for the deriving machinery to find a
      fixpoint when these sort of instance decls are around.  So I
      now constrain *derived* instance decls not to have this form;
      all the tyvars on the left must appear on the right.
      
      On the way I commoned up the previously-separate tcSimplify
      machinery for 'deriving' and 'default' decls with that for
      everything else.   As a result, quite a few files are touched.
      
      I hope I havn't broken anything.
      ae969b47
  34. 20 Dec, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-12-20 11:19:05 by simonpj] · 91c750cb
      simonpj authored
      ---------------------------------------------
      	More type system extensions (for John Hughes)
      	---------------------------------------------
      
      1.  Added a brand-new extension that lets you derive ARBITRARY CLASSES
      for newtypes.  Thus
      
      	newtype Age = Age Int deriving( Eq, Ord, Shape, Ix )
      
      The idea is that the dictionary for the user-defined class Shape Age
      is *identical* to that for Shape Int, so there is really no deriving
      work to do.   This saves you writing the very tiresome instance decl:
      
      	instance Shape Age where
      	   shape_op1 (Age x) = shape_op1 x
      	   shape_op2 (Age x1) (Age x2) = shape_op2 x1 x2
      	   ...etc...
      
      It's more efficient, too, becuase the Shape Age dictionary really
      will be identical to the Shape Int dictionary.
      
      There's an exception for Read and Show, because the derived instance
      *isn't* the same.
      
      There is a complication where higher order stuff is involved.  Here is
      the example John gave:
      
         class StateMonad s m | m -> s where ...
      
         newtype Parser tok m a = Parser (State [tok] (Failure m) a)
      			  deriving( Monad, StateMonad )
      
      Then we want the derived instance decls to be
      
         instance Monad (State [tok] (Failure m)) => Monad (Parser tok m)
         instance StateMonad [tok] (State [tok] (Failure m))
      	 => StateMonad [tok] (Parser tok m)
      
      John is writing up manual entry for all of this, but this commit
      implements it.   I think.
      
      
      2.  Added -fallow-incoherent-instances, and documented it.  The idea
      is that sometimes GHC is over-protective about not committing to a
      particular instance, and the programmer may want to say "commit anyway".
      Here's the example:
      
          class Sat a where
            dict :: a
      
          data EqD a = EqD {eq :: a->a->Bool}
      
          instance Sat (EqD a) => Eq a where
            (==) = eq dict
      
          instance Sat (EqD Integer) where
            dict = EqD{eq=(==)}
      
          instance Eq a => Sat (EqD a) where
            dict = EqD{eq=(==)}
      
          class Collection c cxt | c -> cxt where
            empty :: Sat (cxt a) => c a
            single :: Sat (cxt a) => a -> c a
            union :: Sat (cxt a) => c a -> c a -> c a
            member :: Sat (cxt a) => a -> c a -> Bool
      
          instance Collection [] EqD where
            empty = []
            single x = [x]
            union = (++)
            member = elem
      
      It's an updated attempt to model "Restricted Data Types", if you
      remember my Haskell workshop paper. In the end, though, GHC rejects
      the program (even with fallow-overlapping-instances and
      fallow-undecideable-instances), because there's more than one way to
      construct the Eq instance needed by elem.
      
      Yet all the ways are equivalent! So GHC is being a bit over-protective
      of me, really: I know what I'm doing and I would LIKE it to pick an
      arbitrary one. Maybe a flag fallow-incoherent-instances would be a
      useful thing to add?
      91c750cb
  35. 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
  36. 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