1. 11 Aug, 2005 1 commit
  2. 10 Aug, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-08-10 11:05:06 by simonpj] · e3a4d6c3
      simonpj authored
      It turned out that doing all binding dependency analysis in the typechecker
      meant that the renamer's unused-binding error messages got worse.  So now
      I've put the first dep anal back into the renamer, while the second (which
      is specific to type checking) remains in the type checker.
      
      I've also made the pretty printer sort the decls back into source order
      before printing them (except with -dppr-debug).
      
      Fixes rn041.
      e3a4d6c3
  3. 25 Jul, 2005 1 commit
  4. 22 Jul, 2005 1 commit
  5. 19 Jul, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-07-19 16:44:50 by simonpj] · a7ecdf96
      simonpj authored
      WARNING: this is a big commit.  You might want 
      	to wait a few days before updating, in case I've 
      	broken something.
      
      	However, if any of the changes are what you wanted,
      	please check it out and test!
      
      This commit does three main things:
      
      1. A re-organisation of the way that GHC handles bindings in HsSyn.
         This has been a bit of a mess for quite a while.  The key new
         types are
      
      	-- Bindings for a let or where clause
      	data HsLocalBinds id
      	  = HsValBinds (HsValBinds id)
      	  | HsIPBinds  (HsIPBinds id)
      	  | EmptyLocalBinds
      
      	-- Value bindings (not implicit parameters)
      	data HsValBinds id
      	  = ValBindsIn  -- Before typechecking
      		(LHsBinds id) [LSig id]	-- Not dependency analysed
      					-- Recursive by default
      
      	  | ValBindsOut	-- After typechecking
      		[(RecFlag, LHsBinds id)]-- Dependency analysed
      
      2. Implement Mark Jones's idea of increasing polymoprhism
         by using type signatures to cut the strongly-connected components
         of a recursive group.  As a consequence, GHC no longer insists
         on the contexts of the type signatures of a recursive group
         being identical.
      
         This drove a significant change: the renamer no longer does dependency
         analysis.  Instead, it attaches a free-variable set to each binding,
         so that the type checker can do the dep anal.  Reason: the typechecker
         needs to do *two* analyses:
      	one to find the true mutually-recursive groups
      		(which we need so we can build the right CoreSyn)
      	one to find the groups in which to typecheck, taking
      		account of type signatures
      
      3. Implement non-ground SPECIALISE pragmas, as promised, and as
         requested by Remi and Ross.  Certainly, this should fix the 
         current problem with GHC, namely that if you have
      	g :: Eq a => a -> b -> b
         then you can now specialise thus
      	SPECIALISE g :: Int -> b -> b
          (This didn't use to work.)
      
         However, it goes further than that.  For example:
      	f :: (Eq a, Ix b) => a -> b -> b
         then you can make a partial specialisation
      	SPECIALISE f :: (Eq a) => a -> Int -> Int
      
          In principle, you can specialise f to *any* type that is
          "less polymorphic" (in the sense of subsumption) than f's 
          actual type.  Such as
      	SPECIALISE f :: Eq a => [a] -> Int -> Int
          But I haven't tested that.
      
          I implemented this by doing the specialisation in the typechecker
          and desugarer, rather than leaving around the strange SpecPragmaIds,
          for the specialiser to find.  Indeed, SpecPragmaIds have vanished 
          altogether (hooray).
      
          Pragmas in general are handled more tidily.  There's a new
          data type HsBinds.Prag, which lives in an AbsBinds, and carries
          pragma info from the typechecker to the desugarer.
      
      
      Smaller things
      
      - The loop in the renamer goes via RnExpr, instead of RnSource.
        (That makes it more like the type checker.)
      
      - I fixed the thing that was causing 'check_tc' warnings to be 
        emitted.
      a7ecdf96
  6. 12 Jul, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-07-12 13:38:08 by simonpj] · 2f6d1e5e
      simonpj authored
      Check for an unboxed tuple binding
      	f = (# True, False #)
      
      A fairly recent change, that treats specially non-recursive bindings of a
      single variable, failed to take this into account.
      
      tcfail141 tests this case.  (Was simpl008.)
      -
      2f6d1e5e
  7. 26 May, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-05-26 21:37:13 by simonpj] · 6a18febc
      simonpj authored
      MERGE TO STABLE
      
      Put back in a missing case for higher-rank types. When the
      definition is
      	a) non-recursive
      	b) a function binding
      	c) lacks a type signature
      we want to *infer* a perhaps-higher-rank type for the RHS,
      before making a monomorphically-typed Id for the LHS.
      
      E.g. 	f = \(x :: forall a. a->a) -> (x True, x 'c')
      
      This case got lost in the transition to 6.4
      
      tc194 tests it
      6a18febc
  8. 03 May, 2005 1 commit
  9. 15 Apr, 2005 1 commit
  10. 18 Mar, 2005 1 commit
    • simonmar's avatar
      [project @ 2005-03-18 13:37:27 by simonmar] · d1c1b7d0
      simonmar authored
      Flags cleanup.
      
      Basically the purpose of this commit is to move more of the compiler's
      global state into DynFlags, which is moving in the direction we need
      to go for the GHC API which can have multiple active sessions
      supported by a single GHC instance.
      
      Before:
      
      $ grep 'global_var' */*hs | wc -l
           78
      
      After:
      
      $ grep 'global_var' */*hs | wc -l
           27
      
      Well, it's an improvement.  Most of what's left won't really affect
      our ability to host multiple sessions.
      
      Lots of static flags have become dynamic flags (yay!).  Notably lots
      of flags that we used to think of as "driver" flags, like -I and -L,
      are now dynamic.  The most notable static flags left behind are the
      "way" flags, eg. -prof.  It would be nice to fix this, but it isn't
      urgent.
      
      On the way, lots of cleanup has happened.  Everything related to
      static and dynamic flags lives in StaticFlags and DynFlags
      respectively, and they share a common command-line parser library in
      CmdLineParser.  The flags related to modes (--makde, --interactive
      etc.) are now private to the front end: in fact private to Main
      itself, for now.
      d1c1b7d0
  11. 17 Mar, 2005 1 commit
  12. 07 Mar, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-03-07 15:16:58 by simonpj] · bcacf0b7
      simonpj authored
      -----------------------------------------
             Fix scoping bug for quantified type variables
      	-----------------------------------------
      
      	Merge to STABLE
      
      When instantiating a declaration type signature, make sure to instantiate
      fresh names for non-scoped type variables, else they may be spuriously shared.
      Turns out that the test lib/Generics/reify tests this, which is good.
      
      Comments are with TcMType.tcInstSigType
      bcacf0b7
  13. 01 Mar, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-03-01 21:40:40 by simonpj] · ff818166
      simonpj authored
      Type signatures and skolem constants (again)
      		Merge to STABLE
      
      This commit lays to rest the vexed question of skolem constants
      and type signatures.  My fix last week made type-signature variables
      into ordinary meta type variables, because they can be unified
      together (see Note [Signature skolems] in TcType).  But that was wrong
      becuase GADTs will only refine skolems.
      
      So this commit extends TcTyVarDetails with a new constructors, SigSkolTv,
      which is a skolem (like SkolemTv) but is unifiable (like MetaTv).  It's
      a bit of a hack, but the code came out quite nicely.
      
      Now the GADT tests work.
      ff818166
  14. 25 Feb, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-02-25 13:06:31 by simonpj] · 8e67f550
      simonpj authored
      ---------------------------------------------
      Type signatures are no longer instantiated with skolem constants
      	---------------------------------------------
      
      	Merge to STABLE
      
      Consider
      
        p :: a
        q :: b
        (p,q,r) = (r,r,p)
      
      Here, 'a' and 'b' end up being the same, because they are both bound
      to the type for 'r', which is just a meta type variable.  So 'a' and 'b'
      can't be skolems.
      
      Sigh.  This commit goes back to an earlier way of doing things, by
      arranging that type signatures get instantiated with *meta* type
      variables; then at the end we must check that they have not been
      unified with types, nor with each other.
      
      This is a real bore.  I had to do quite a bit of related fiddling around
      to make error messages come out right.  Improved one or two.
      
      Also a small unrelated fix to make
      	:i (:+)
      print with parens in ghci.  Sorry this got mixed up in the same commit.
      8e67f550
  15. 04 Feb, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-02-04 17:24:01 by simonpj] · c36a2f9b
      simonpj authored
      ------------------------------------------------------
      	Report top-level implicit parameter errors more nicely
      	------------------------------------------------------
      
      Consider
          module Main where
      
      	main = let ?x = 5 in print foo
      
      	foo = woggle 3
      
      	woggle :: (?x :: Int) => Int -> Int
      	woggle y = ?x + y
      
      GHC's current rules say that 'foo' is monomorphic, so we get
      	foo :: Int
      but we also get an unbound top-level constraint (?x::Int).  GHC 6.2 emits a
      message like:
           Unbound implicit parameter (?x::Int)
           arising from use of `woggle' at ...
      
      The point is that THERE IS NO WAY FOR THIS CONSTRAINT TO GET BOUND,
      because we don't have a top-level binding form for implicit parameters.
      So it's stupid for 'foo' to be monomorphic.
      
      This commit improves matters by giving a much nicer error message:
      
           Implicit parameters escape from the monomorphic top-level binding(s) of `foo':
             ?x::Int arising from use of `woggle' at tcfail130.hs:10:6-11
           Probably fix: add type signatures for the top-level binding(s)
           When generalising the type(s) for `foo'
      c36a2f9b
  16. 31 Jan, 2005 1 commit
  17. 27 Jan, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-01-27 10:44:00 by simonpj] · 508a505e
      simonpj authored
      --------------------------------------------
                Replace hi-boot files with hs-boot files
        	--------------------------------------------
      
      This major commit completely re-organises the way that recursive modules
      are dealt with.
      
        * It should have NO EFFECT if you do not use recursive modules
      
        * It is a BREAKING CHANGE if you do
      
      ====== Warning: .hi-file format has changed, so if you are
      ======		updating into an existing HEAD build, you'll
      ======		need to make clean and re-make
      
      
      The details:  [documentation still to be done]
      
      * Recursive loops are now broken with Foo.hs-boot (or Foo.lhs-boot),
        not Foo.hi-boot
      
      * An hs-boot files is a proper source file.  It is compiled just like
        a regular Haskell source file:
      	ghc Foo.hs		generates Foo.hi, Foo.o
      	ghc Foo.hs-boot		generates Foo.hi-boot, Foo.o-boot
      
      * hs-boot files are precisely a subset of Haskell. In particular:
      	- they have the same import, export, and scoping rules
      	- errors (such as kind errors) in hs-boot files are checked
        You do *not* need to mention the "original" name of something in
        an hs-boot file, any more than you do in any other Haskell module.
      
      * The Foo.hi-boot file generated by compiling Foo.hs-boot is a machine-
        generated interface file, in precisely the same format as Foo.hi
      
      * When compiling Foo.hs, its exports are checked for compatibility with
        Foo.hi-boot (previously generated by compiling Foo.hs-boot)
      
      * The dependency analyser (ghc -M) knows about Foo.hs-boot files, and
        generates appropriate dependencies.  For regular source files it
        generates
      	Foo.o : Foo.hs
      	Foo.o : Baz.hi		-- Foo.hs imports Baz
      	Foo.o : Bog.hi-boot	-- Foo.hs source-imports Bog
      
        For a hs-boot file it generates similar dependencies
      	Bog.o-boot : Bog.hs-boot
      	Bog.o-boot : Nib.hi	-- Bog.hs-boto imports Nib
      
      * ghc -M is also enhanced to use the compilation manager dependency
        chasing, so that
      	ghc -M Main
        will usually do the job.  No need to enumerate all the source files.
      
      * The -c flag is no longer a "compiler mode". It simply means "omit the
        link step", and synonymous with -no-link.
      508a505e
  18. 24 Dec, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-12-24 11:02:39 by simonpj] · 0ee11df0
      simonpj authored
      Further wibbles to the scoped-tyvar story.
      
      This commit tidies up the ATyVar in TcTyThing, making it
      	ATyVar Name Type
      instead of the previous misleading
      	ATyVar TyVar Type
      
      But the main thing is that we must take care with definitions
      like this:
      
      	type T a = forall b. b -> (a,b)
      
      	f :: forall c. T c
      	f = ...
      
      Here, we want only 'c' to scope over the RHS of f.  The renamer ensures
      that... but we must also take care that we freshly instantiate the 
      expanded type signature (forall c b. b -> (c,b)) before checking f's RHS,
      so that we don't get false sharing between uses of T.
      0ee11df0
  19. 22 Dec, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-12-22 16:58:34 by simonpj] · 20e39e0e
      simonpj authored
      ----------------------------------------
      	     Add more scoped type variables
      	----------------------------------------
      
      Now the top-level forall'd variables of a type signature scope
      over the right hand side of that function.
      
      	f :: a -> a
      	f x = ....
      
      The type variable 'a' is in scope in the RHS, and in f's patterns.
      
      It's implied by -fglasgow-exts, but can also be switched off independently
      using -fscoped-type-variables (and the -fno variant)
      20e39e0e
  20. 20 Dec, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-12-20 17:16:24 by simonpj] · c45a0ac5
      simonpj authored
      --------------------------------
      	Deal properly with dual-renaming
      	--------------------------------
      
      When comparing types and terms, and during matching, we are faced
      with 
      	\x.e1	~   \y.e2
      
      There are many pitfalls here, and GHC has never done the job properly.
      Now, at last it does, using a new abstraction VarEnv.RnEnv2.  See
      comments there for how it works.
      
      There are lots of consequential changes to use the new stuff, especially
      in 
      	types/Type (type comparison), 
      	types/Unify (matching on types)
      	coreSyn/CoreUtils (equality on expressions), 
      	specialise/Rules (matching).
      
      I'm not 100% certain of that I've covered all the bases, so let me
      know if something unexpected happens after you update.  Maybe wait until
      a nightly build has worked ok first!
      c45a0ac5
  21. 02 Dec, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-12-02 17:18:15 by simonpj] · 759739c6
      simonpj authored
      Sorry for the fact that there are overlapping three commits in here...
      
      1.  Make -fno-monomorphism-restriction 
          and -fno-implicit-prelude reversible, like other flags
      
      2.  Fix a wibble in the new ImportAvails story, in RnNames.mkExportAvails
      
      3.  Fix a Template Haskell bug that meant that top-level names created
          with newName were not made properly unique.
      759739c6
  22. 11 Nov, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-11-11 16:44:33 by simonpj] · dfec17bf
      simonpj authored
      ---------------------------------
           Buglet in the handling of unlifted bindings
      	---------------------------------
      
      Unlifted bindings, like
      	let I# v = ... in ...
      can't be generalised.  In teh transition to GADTs I introduced a bug
      that accidentally discarded some necessary dictionary bindings.
      
      This commit fixes it by moving the test for unlifted bindings to a
      much earlier point in tcBindWithSigs, which seems a lot cleaner to me.
      dfec17bf
  23. 01 Oct, 2004 1 commit
  24. 30 Sep, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-09-30 10:35:15 by simonpj] · 23f40f0e
      simonpj authored
      ------------------------------------
      	Add Generalised Algebraic Data Types
      	------------------------------------
      
      This rather big commit adds support for GADTs.  For example,
      
          data Term a where
       	  Lit :: Int -> Term Int
      	  App :: Term (a->b) -> Term a -> Term b
      	  If  :: Term Bool -> Term a -> Term a
      	  ..etc..
      
          eval :: Term a -> a
          eval (Lit i) = i
          eval (App a b) = eval a (eval b)
          eval (If p q r) | eval p    = eval q
          		    | otherwise = eval r
      
      
      Lots and lots of of related changes throughout the compiler to make
      this fit nicely.
      
      One important change, only loosely related to GADTs, is that skolem
      constants in the typechecker are genuinely immutable and constant, so
      we often get better error messages from the type checker.  See
      TcType.TcTyVarDetails.
      
      There's a new module types/Unify.lhs, which has purely-functional
      unification and matching for Type. This is used both in the typechecker
      (for type refinement of GADTs) and in Core Lint (also for type refinement).
      23f40f0e
  25. 19 Jul, 2004 1 commit
  26. 06 May, 2004 1 commit
  27. 30 Dec, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-12-30 16:29:17 by simonpj] · f714e6b6
      simonpj authored
      ----------------------------
              Re-do kind inference (again)
      	----------------------------
      
         [WARNING: interface file binary representation has
         (as usual) changed slightly; recompile your libraries!]
      
      Inspired by the lambda-cube, for some time GHC has used
      	type Kind = Type
      That is, kinds were represented by the same data type as types.
      
      But GHC also supports unboxed types and unboxed tuples, and these
      complicate the kind system by requiring a sub-kind relationship.
      Notably, an unboxed tuple is acceptable as the *result* of a
      function but not as an *argument*.  So we have the following setup:
      
      		 ?
      		/ \
      	       /   \
      	      ??   (#)
      	     /  \
                  *   #
      
      where	*    [LiftedTypeKind]   means a lifted type
      	#    [UnliftedTypeKind] means an unlifted type
      	(#)  [UbxTupleKind]     means unboxed tuple
      	??   [ArgTypeKind]      is the lub of *,#
      	?    [OpenTypeKind]	means any type at all
      
      In particular:
      
        error :: forall a:?. String -> a
        (->)  :: ?? -> ? -> *
        (\(x::t) -> ...)	Here t::?? (i.e. not unboxed tuple)
      
      All this has beome rather difficult to accommodate with Kind=Type, so this
      commit splits the two.
      
        * Kind is a distinct type, defined in types/Kind.lhs
      
        * IfaceType.IfaceKind disappears: we just re-use Kind.Kind
      
        * TcUnify.unifyKind is a distinct unifier for kinds
      
        * TyCon no longer needs KindCon and SuperKindCon variants
      
        * TcUnify.zapExpectedType takes an expected Kind now, so that
          in TcPat.tcMonoPatBndr we can express that the bound variable
          must have an argTypeKind (??).
      
      The big change is really that kind inference is much more systematic and
      well behaved.  In particular, a kind variable can unify only with a
      "simple kind", which is built from * and (->).  This deals neatly
      with awkward questions about how we can combine sub-kinding with type
      inference.
      
      Lots of small consequential changes, especially to the kind-checking
      plumbing in TcTyClsDecls.  (We played a bit fast and loose before, and
      now we have to be more honest, in particular about how kind inference
      works for type synonyms.  They can have kinds like (* -> #), so
      
      This cures two long-standing SourceForge bugs
      
      * 753777 (tcfail115.hs), which used erroneously to pass,
        but crashed in the code generator
            type T a = Int -> (# Int, Int #)
            f :: T a -> T a
            f t = \x -> case t x of r -> r
      
      * 753780 (tc167.hs), which used erroneously to fail
            f :: (->) Int# Int#
      
      
      Still, the result is not entirely satisfactory.  In particular
      
      * The error message from tcfail115 is pretty obscure
      
      * SourceForge bug 807249 (Instance match failure on openTypeKind)
        is not fixed.  Alas.
      f714e6b6
  28. 17 Dec, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-12-17 11:29:40 by simonpj] · ca0b7c66
      simonpj authored
      -----------------------------------------------------
        Fix a subtle loop in the context-reduction machinery
        ----------------------------------------------------
      
      This bug was provoked by a recent change: when trying to prove
      a constraint C, TcSimplify.reduce now adds C to the database before
      trying to prove C, thus building recursive dictionaries.
      
      Two bugs
      a) If we add C's superclasses (which we were) we can now build a
         bogusly-recursive dictionary (see Note [SUPERCLASS-LOOP]).
         Solution: in reduce, add C only (via addIrred NoSCs) and then
         later use addWanted to add its definition plus SCs.
      
      b) Since we can have recursive definitions, the superclass-loop
         handling machinery (findAllDeps) must carry its visited-set
         with it (which it was not doing before)
      
      
      The main file is TcSimplify; but I modified a bunch of others to
      take advantage of new function extendVarSetList
      ca0b7c66
  29. 10 Dec, 2003 1 commit
    • simonmar's avatar
      [project @ 2003-12-10 14:15:16 by simonmar] · 55042138
      simonmar authored
      Add accurate source location annotations to HsSyn
      -------------------------------------------------
      
      Every syntactic entity in HsSyn is now annotated with a SrcSpan, which
      details the exact beginning and end points of that entity in the
      original source file.  All honest compilers should do this, and it was
      about time GHC did the right thing.
      
      The most obvious benefit is that we now have much more accurate error
      messages; when running GHC inside emacs for example, the cursor will
      jump to the exact location of an error, not just a line somewhere
      nearby.  We haven't put a huge amount of effort into making sure all
      the error messages are accurate yet, so there could be some tweaking
      still needed, although the majority of messages I've seen have been
      spot-on.
      
      Error messages now contain a column number in addition to the line
      number, eg.
      
         read001.hs:25:10: Variable not in scope: `+#'
      
      To get the full text span info, use the new option -ferror-spans.  eg.
      
         read001.hs:25:10-11: Variable not in scope: `+#'
      
      I'm not sure whether we should do this by default.  Emacs won't
      understand the new error format, for one thing.
      
      In a more elaborate editor setting (eg. Visual Studio), we can arrange
      to actually highlight the subexpression containing an error.  Eventually
      this information will be used so we can find elements in the abstract
      syntax corresponding to text locations, for performing high-level editor
      functions (eg. "tell me the type of this expression I just highlighted").
      
      Performance of the compiler doesn't seem to be adversely affected.
      Parsing is still quicker than in 6.0.1, for example.
      
      Implementation:
      
      This was an excrutiatingly painful change to make: both Simon P.J. and
      myself have been working on it for the last three weeks or so.  The
      basic changes are:
      
       - a new datatype SrcSpan, which represents a beginning and end position
         in a source file.
      
       - To reduce the pain as much as possible, we also defined:
      
            data Located e = L SrcSpan e
      
       - Every datatype in HsSyn has an equivalent Located version.  eg.
      
            type LHsExpr id = Located (HsExpr id)
      
         and pretty much everywhere we used to use HsExpr we now use
         LHsExpr.  Believe me, we thought about this long and hard, and
         all the other options were worse :-)
      
      
      Additional changes/cleanups we made at the same time:
      
        - The abstract syntax for bindings is now less arcane.  MonoBinds
          and HsBinds with their built-in list constructors have gone away,
          replaced by HsBindGroup and HsBind (see HsSyn/HsBinds.lhs).
      
        - The various HsSyn type synonyms have now gone away (eg. RdrNameHsExpr,
          RenamedHsExpr, and TypecheckedHsExpr are now HsExpr RdrName,
          HsExpr Name, and HsExpr Id respectively).
      
        - Utilities over HsSyn are now collected in a new module HsUtils.
          More stuff still needs to be moved in here.
      
        - MachChar now has a real Char instead of an Int.  All GHC versions that
          can compile GHC now support 32-bit Chars, so this was a simplification.
      55042138
  30. 21 Oct, 2003 1 commit
    • simonpj's avatar
      [project @ 2003-10-21 12:54:17 by simonpj] · 1bade0c9
      simonpj authored
      1. A tiresome change to HsType, to keep a record of whether or not
         the HsForAll was originally explicitly-quantified.  This is
         solely so that the type checker can print out messages that
         show the source code the programmer wrote.  Tiresome but
         easy.
      
      2. Improve reporting of kind errors.
      1bade0c9
  31. 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
  32. 24 Sep, 2003 1 commit
  33. 20 Sep, 2003 1 commit
    • ross's avatar
      [project @ 2003-09-20 17:26:46 by ross] · dbaa3bb3
      ross authored
      Re-arrange the interface to TcMatches to allow typechecking of case
      commands (part of arrow notation):
      
      * replace the export of the internal tcGRHSs with a more specific
        tcGRHSsPat for checking PatMonoBinds.
      
      * generalize match contexts in the same way as stmt contexts, to include
        a typechecker for the bodies of alts.
      
      This should probably be reviewed, but I hope it can make it into STABLE
      after a while.
      dbaa3bb3
  34. 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
  35. 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
  36. 21 Feb, 2003 2 commits
  37. 06 Jan, 2003 1 commit
  38. 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
  39. 23 Oct, 2002 1 commit
    • simonpj's avatar
      [project @ 2002-10-23 14:30:00 by simonpj] · 203a687f
      simonpj authored
      ------------------------------------------------
      	Allow implicit-parameter bindings anywhere that
      		a normal binding group is allowed.
      	------------------------------------------------
      
      That is, you can have implicit parameters
      
      	* in a let binding
      	* in a where clause (but then you can't have non-implicit
      	  ones as well)
      	* in a let group in a list comprehension or monad do-notation
      
      The implementation is simple: just add IPBinds to the allowable forms of HsBinds,
      and remove the HsWith expression form altogether.   (It now comes in via the
      HsLet form.)
      
      It'a a nice generalisation really.  Needs a bit of documentation, which I'll do next.
      203a687f