1. 11 Aug, 2006 2 commits
  2. 22 Jul, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Add -fmono-pat-binds, and make it the default · 10ffe4f7
      simonpj@microsoft.com authored
      In Haskell 98, pattern bindings are generalised.  Thus in
      	(f,g) = (\x->x, \y->y)
      both f and g will get polymorphic types.  I have become convinced
      that generalisation for pattern-bound variables is just a bridge
      toof far. It is (I claim) almost never needed, and it adds significant
      complication.  (All the more so if we add bang patterns.)
      So the flag -fmono-pat-binds switches off generalisation for pattern
      bindings.  (A single variable is treated as a degnerate funtction
      Furthremore, as an experiment, I'm making it the default.  I want
      to see how many progarms fail with monomorphic pattern bindings.
      You can recover the standard behaviour with -fno-mono-pa-binds.
  3. 21 Jun, 2006 1 commit
  4. 12 Jun, 2006 1 commit
  5. 14 Apr, 2006 1 commit
  6. 07 Apr, 2006 1 commit
    • Simon Marlow's avatar
      Reorganisation of the source tree · 0065d5ab
      Simon Marlow authored
      Most of the other users of the fptools build system have migrated to
      Cabal, and with the move to darcs we can now flatten the source tree
      without losing history, so here goes.
      The main change is that the ghc/ subdir is gone, and most of what it
      contained is now at the top level.  The build system now makes no
      pretense at being multi-project, it is just the GHC build system.
      No doubt this will break many things, and there will be a period of
      instability while we fix the dependencies.  A straightforward build
      should work, but I haven't yet fixed binary/source distributions.
      Changes to the Building Guide will follow, too.
  7. 02 Mar, 2006 1 commit
  8. 03 Feb, 2006 1 commit
  9. 01 Feb, 2006 1 commit
  10. 30 Jan, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Add mkHsCoerce to avoid junk in typechecked code · eb57096f
      simonpj@microsoft.com authored
      Avoiding identity coercions is a Good Thing generally, but
      it turns out that the desugarer has trouble recognising 
      'otherwise' and 'True' guards if they are wrapped in an
      identity coercion; and that leads to bogus overlap warnings.
  11. 25 Jan, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Simon's big boxy-type commit · ac10f840
      simonpj@microsoft.com authored
      This very large commit adds impredicativity to GHC, plus
      numerous other small things.
      *** WARNING: I have compiled all the libraries, and
      ***	     a stage-2 compiler, and everything seems
      ***	     fine.  But don't grab this patch if you 
      ***	     can't tolerate a hiccup if something is
      ***	     broken.
      The big picture is this:
      a) GHC handles impredicative polymorphism, as described in the
         "Boxy types: type inference for higher-rank types and
         impredicativity" paper
      b) GHC handles GADTs in the new simplified (and very sligtly less
         epxrssive) way described in the
         "Simple unification-based type inference for GADTs" paper
      But there are lots of smaller changes, and since it was pre-Darcs
      they are not individually recorded.
      Some things to watch out for:
      c)   The story on lexically-scoped type variables has changed, as per
           my email.  I append the story below for completeness, but I 
           am still not happy with it, and it may change again.  In particular,
           the new story does not allow a pattern-bound scoped type variable
           to be wobbly, so (\(x::[a]) -> ...) is usually rejected.  This is
           more restrictive than before, and we might loosen up again.
      d)   A consequence of adding impredicativity is that GHC is a bit less
           gung ho about converting automatically between
        	(ty1 -> forall a. ty2)    and    (forall a. ty1 -> ty2)
           In particular, you may need to eta-expand some functions to make
           typechecking work again.
           Furthermore, functions are now invariant in their argument types,
           rather than being contravariant.  Again, the main consequence is
           that you may occasionally need to eta-expand function arguments when
           using higher-rank polymorphism.
      Please test, and let me know of any hiccups
      Scoped type variables in GHC
      	January 2006
      0) Terminology.
         A *pattern binding* is of the form
      	pat = rhs
         A *function binding* is of the form
      	f pat1 .. patn = rhs
         A binding of the formm
      	var = rhs
         is treated as a (degenerate) *function binding*.
         A *declaration type signature* is a separate type signature for a
         let-bound or where-bound variable:
      	f :: Int -> Int
         A *pattern type signature* is a signature in a pattern: 
      	\(x::a) -> x
      	f (x::a) = x
         A *result type signature* is a signature on the result of a
         function definition:
      	f :: forall a. [a] -> a
      	head (x:xs) :: a = x
         The form
      	x :: a = rhs
         is treated as a (degnerate) function binding with a result
         type signature, not as a pattern binding.
      1) The main invariants:
           A) A lexically-scoped type variable always names a (rigid)
       	type variable (not an arbitrary type).  THIS IS A CHANGE.
              Previously, a scoped type variable named an arbitrary *type*.
           B) A type signature always describes a rigid type (since
      	its free (scoped) type variables name rigid type variables).
      	This is also a change, a consequence of (A).
           C) Distinct lexically-scoped type variables name distinct
      	rigid type variables.  This choice is open; 
      2) Scoping
      2(a) If a declaration type signature has an explicit forall, those type
         variables are brought into scope in the right hand side of the 
         corresponding binding (plus, for function bindings, the patterns on
         the LHS).  
      	f :: forall a. a -> [a]
      	f (x::a) = [x :: a, x]
         Both occurences of 'a' in the second line are bound by 
         the 'forall a' in the first line
         A declaration type signature *without* an explicit top-level forall
         is implicitly quantified over all the type variables that are
         mentioned in the type but not already in scope.  GHC's current
         rule is that this implicit quantification does *not* bring into scope
         any new scoped type variables.
      	f :: a -> a
      	f x = ...('a' is not in scope here)...
         This gives compatibility with Haskell 98
      2(b) A pattern type signature implicitly brings into scope any type
         variables mentioned in the type that are not already into scope.
         These are called *pattern-bound type variables*.
      	g :: a -> a -> [a]
      	g (x::a) (y::a) = [y :: a, x]
         The pattern type signature (x::a) brings 'a' into scope.
         The 'a' in the pattern (y::a) is bound, as is the occurrence on 
         the RHS.  
         A pattern type siganture is the only way you can bring existentials 
         into scope.
      	data T where
      	  MkT :: forall a. a -> (a->Int) -> T
      	f x = case x of
      		MkT (x::a) f -> f (x::a)
      2a) QUESTION
      	class C a where
      	  op :: forall b. b->a->a
      	instance C (T p q) where
      	  op = <rhs>
          Clearly p,q are in scope in <rhs>, but is 'b'?  Not at the moment.
          Nor can you add a type signature for op in the instance decl.
          You'd have to say this:
      	instance C (T p q) where
      	  op = let op' :: forall b. ...
      	           op' = <rhs>
      	       in op'
      3) A pattern-bound type variable is allowed only if the pattern's
         expected type is rigid.  Otherwise we don't know exactly *which*
         skolem the scoped type variable should be bound to, and that means
         we can't do GADT refinement.  This is invariant (A), and it is a 
         big change from the current situation.
      	f (x::a) = x	-- NO; pattern type is wobbly
      	g1 :: b -> b
      	g1 (x::b) = x	-- YES, because the pattern type is rigid
      	g2 :: b -> b
      	g2 (x::c) = x	-- YES, same reason
      	h :: forall b. b -> b
      	h (x::b) = x	-- YES, but the inner b is bound
      	k :: forall b. b -> b
      	k (x::c) = x	-- NO, it can't be both b and c
      3a) You cannot give different names for the same type variable in the same scope
          (Invariant (C)):
      	f1 :: p -> p -> p		-- NO; because 'a' and 'b' would be
      	f1 (x::a) (y::b) = (x::a)	--     bound to the same type variable
      	f2 :: p -> p -> p		-- OK; 'a' is bound to the type variable
      	f2 (x::a) (y::a) = (x::a)	--     over which f2 is quantified
      					-- NB: 'p' is not lexically scoped
      	f3 :: forall p. p -> p -> p	-- NO: 'p' is now scoped, and is bound to
      	f3 (x::a) (y::a) = (x::a)	--     to the same type varialble as 'a'
      	f4 :: forall p. p -> p -> p	-- OK: 'p' is now scoped, and its occurences
      	f4 (x::p) (y::p) = (x::p)	--     in the patterns are bound by the forall
      3b) You can give a different name to the same type variable in different
          disjoint scopes, just as you can (if you want) give diferent names to 
          the same value parameter
      	g :: a -> Bool -> Maybe a
      	g (x::p) True  = Just x  :: Maybe p
      	g (y::q) False = Nothing :: Maybe q
      3c) Scoped type variables respect alpha renaming. For example, 
          function f2 from (3a) above could also be written:
      	f2' :: p -> p -> p
      	f2' (x::b) (y::b) = x::b
         where the scoped type variable is called 'b' instead of 'a'.
      4) Result type signatures obey the same rules as pattern types signatures.
         In particular, they can bind a type variable only if the result type is rigid
      	f x :: a = x	-- NO
      	g :: b -> b
      	g x :: b = x	-- YES; binds b in rhs
      5) A *pattern type signature* in a *pattern binding* cannot bind a 
         scoped type variable
      	(x::a, y) = ...		-- Legal only if 'a' is already in scope
         Reason: in type checking, the "expected type" of the LHS pattern is
         always wobbly, so we can't bind a rigid type variable.  (The exception
         would be for an existential type variable, but existentials are not
         allowed in pattern bindings either.)
         Even this is illegal
      	f :: forall a. a -> a
      	f x = let ((y::b)::a, z) = ... 
         Here it looks as if 'b' might get a rigid binding; but you can't bind
         it to the same skolem as a.
      6) Explicitly-forall'd type variables in the *declaration type signature(s)*
         for a *pattern binding* do not scope AT ALL.
      	x :: forall a. a->a	  -- NO; the forall a does 
      	Just (x::a->a) = Just id  --     not scope at all
      	y :: forall a. a->a
      	Just y = Just (id :: a->a)  -- NO; same reason
         THIS IS A CHANGE, but one I bet that very few people will notice.
         Here's why:
      	strange :: forall b. (b->b,b->b)
      	strange = (id,id)
      	x1 :: forall a. a->a
      	y1 :: forall b. b->b
      	(x1,y1) = strange
          This is legal Haskell 98 (modulo the forall). If both 'a' and 'b'
          both scoped over the RHS, they'd get unified and so cannot stand
          for distinct type variables. One could *imagine* allowing this:
      	x2 :: forall a. a->a
      	y2 :: forall a. a->a
      	(x2,y2) = strange
          using the very same type variable 'a' in both signatures, so that
          a single 'a' scopes over the RHS.  That seems defensible, but odd,
          because though there are two type signatures, they introduce just
          *one* scoped type variable, a.
      7) Possible extension.  We might consider allowing
      	\(x :: [ _ ]) -> <expr>
          where "_" is a wild card, to mean "x has type list of something", without
          naming the something.
  12. 27 Oct, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-10-27 14:35:20 by simonpj] · 958924a2
      simonpj authored
      Add a new pragma: SPECIALISE INLINE
      This amounts to adding an INLINE pragma to the specialised version
      of the function.  You can add phase stuff too (SPECIALISE INLINE [2]),
      and NOINLINE instead of INLINE.
      The reason for doing this is to support inlining of type-directed
      recursive functions.  The main example is this:
        -- non-uniform array type
        data Arr e where
          ArrInt  :: !Int -> ByteArray#       -> Arr Int
          ArrPair :: !Int -> Arr e1 -> Arr e2 -> Arr (e1, e2)
        (!:) :: Arr e -> Int -> e
        {-# SPECIALISE INLINE (!:) :: Arr Int -> Int -> Int #-}
        {-# SPECIALISE INLINE (!:) :: Arr (a, b) -> Int -> (a, b) #-}
        ArrInt  _ ba    !: (I# i) = I# (indexIntArray# ba i)
        ArrPair _ a1 a2 !: i      = (a1 !: i, a2 !: i)
      If we use (!:) at a particular array type, we want to inline (:!),
      which is recursive, until all the type specialisation is done.
      On the way I did a bit of renaming and tidying of the way that
      pragmas are carried, so quite a lot of files are touched in a
      fairly trivial way.
  13. 11 Aug, 2005 1 commit
  14. 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.
  15. 25 Jul, 2005 1 commit
  16. 22 Jul, 2005 1 commit
  17. 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 
  18. 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.)
  19. 26 May, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-05-26 21:37:13 by simonpj] · 6a18febc
      simonpj authored
      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
  20. 03 May, 2005 1 commit
  21. 15 Apr, 2005 1 commit
  22. 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.
      $ grep 'global_var' */*hs | wc -l
      $ grep 'global_var' */*hs | wc -l
      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
      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.
  23. 17 Mar, 2005 1 commit
  24. 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
  25. 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.
  26. 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
        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.
  27. 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
          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 ...
      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'
  28. 31 Jan, 2005 1 commit
  29. 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
      	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.
  30. 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.
  31. 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)
  32. 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
      	\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
      	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!
  33. 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.
  34. 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.
  35. 01 Oct, 2004 1 commit
  36. 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
          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
      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).
  37. 19 Jul, 2004 1 commit
  38. 06 May, 2004 1 commit
  39. 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
      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.