1. 21 Jun, 2007 2 commits
    • simonpj@microsoft.com's avatar
      e2b5796d
    • David Himmelstrup's avatar
      Add several new record features · 2eb04ca0
      David Himmelstrup authored
      1. Record disambiguation (-fdisambiguate-record-fields)
      
      In record construction and pattern matching (although not
      in record updates) it is clear which field name is intended
      even if there are several in scope.  This extension uses
      the constructor to disambiguate.  Thus
      	C { x=3 }
      uses the 'x' field from constructor C (assuming there is one)
      even if there are many x's in scope.
      
      
      2. Record punning (-frecord-puns)
      
      In a record construction or pattern match or update you can 
      omit the "=" part, thus
      	C { x, y }
      This is just syntactic sugar for
      	C { x=x, y=y }
      
      
      3.  Dot-dot notation for records (-frecord-dot-dot)
      
      In record construction or pattern match (but not update) 
      you can use ".." to mean "all the remaining fields".  So
      
      	C { x=v, .. }
      
      means to fill in the remaining fields to give
      
      	C { x=v, y=y }
      
      (assuming C has fields x and y).  This might reasonably
      considered very dodgy stuff.  For pattern-matching it brings
      into scope a bunch of things that are not explictly mentioned;
      and in record construction it just picks whatver 'y' is in
      scope for the 'y' field.   Still, Lennart Augustsson really
      wants it, and it's a feature that is extremely easy to explain.
      
      
      Implementation
      ~~~~~~~~~~~~~~
      I thought of using the "parent" field in the GlobalRdrEnv, but
      that's really used for import/export and just isn't right for this.
      For example, for import/export a field is a subordinate of the *type
      constructor* whereas here we need to know what fields belong to a
      particular *data* constructor.
      
      The main thing is that we need to map a data constructor to its
      fields, and we need to do so in the renamer.   For imported modules
      it's easy: just look in the imported TypeEnv.  For the module being
      compiled, we make a new field tcg_field_env in the TcGblEnv.
      The important functions are
      	RnEnv.lookupRecordBndr
      	RnEnv.lookupConstructorFields
      
      There is still a significant infelicity in the way the renamer
      works on patterns, which I'll tackle next.
      
      
      I also did quite a bit of refactoring in the representation of
      record fields (mainly in HsPat).***END OF DESCRIPTION***
      
      Place the long patch description above the ***END OF DESCRIPTION*** marker.
      The first line of this file will be the patch name.
      
      
      This patch contains the following changes:
      
      M ./compiler/deSugar/Check.lhs -3 +5
      M ./compiler/deSugar/Coverage.lhs -6 +7
      M ./compiler/deSugar/DsExpr.lhs -6 +13
      M ./compiler/deSugar/DsMeta.hs -8 +8
      M ./compiler/deSugar/DsUtils.lhs -1 +1
      M ./compiler/deSugar/MatchCon.lhs -2 +2
      M ./compiler/hsSyn/Convert.lhs -3 +3
      M ./compiler/hsSyn/HsDecls.lhs -9 +25
      M ./compiler/hsSyn/HsExpr.lhs -13 +3
      M ./compiler/hsSyn/HsPat.lhs -25 +63
      M ./compiler/hsSyn/HsUtils.lhs -3 +3
      M ./compiler/main/DynFlags.hs +6
      M ./compiler/parser/Parser.y.pp -13 +17
      M ./compiler/parser/RdrHsSyn.lhs -16 +18
      M ./compiler/rename/RnBinds.lhs -2 +2
      M ./compiler/rename/RnEnv.lhs -22 +82
      M ./compiler/rename/RnExpr.lhs -34 +12
      M ./compiler/rename/RnHsSyn.lhs -3 +2
      M ./compiler/rename/RnSource.lhs -50 +78
      M ./compiler/rename/RnTypes.lhs -50 +84
      M ./compiler/typecheck/TcExpr.lhs -18 +18
      M ./compiler/typecheck/TcHsSyn.lhs -20 +21
      M ./compiler/typecheck/TcPat.lhs -8 +6
      M ./compiler/typecheck/TcRnMonad.lhs -6 +15
      M ./compiler/typecheck/TcRnTypes.lhs -2 +11
      M ./compiler/typecheck/TcTyClsDecls.lhs -3 +4
      M ./docs/users_guide/flags.xml +7
      M ./docs/users_guide/glasgow_exts.xml +42
      2eb04ca0
  2. 18 Jun, 2007 1 commit
  3. 20 Jun, 2007 1 commit
  4. 05 Jun, 2007 1 commit
  5. 02 May, 2007 1 commit
  6. 22 Apr, 2007 1 commit
    • simonpj@microsoft.com's avatar
      Fixes to datacon wrappers for indexed data types · 70918cf4
      simonpj@microsoft.com authored
      nominolo@gmail.com pointed out (Trac #1204) that indexed data types
      aren't quite right. I investigated and found that the wrapper
      functions for indexed data types, generated in MkId, are really very
      confusing.  In particular, we'd like these combinations to work
      	newtype + indexed data type
      	GADT + indexted data type
      The wrapper situation gets a bit complicated!  
      
      I did a bit of refactoring, and improved matters, I think.  I am not
      certain that I have gotten it right yet, but I think it's better.
      I'm committing it now becuase it's been on my non-backed-up laptop for
      a month and I want to get it into the repo. I don't think I've broken
      anything, but I don't regard it as 'done'.
      70918cf4
  7. 04 Feb, 2007 1 commit
  8. 21 Dec, 2006 1 commit
    • lennart@augustsson.net's avatar
      Add support for overloaded string literals. · 90dc9026
      lennart@augustsson.net authored
      The class is named IsString with the single method fromString.
      Overloaded strings work the same way as overloaded numeric literals.
      In expressions a string literals gets a fromString applied to it.
      In a pattern there will be an equality comparison with the fromString:ed literal.
      
      Use -foverloaded-strings to enable this extension.
       
      90dc9026
  9. 03 Jan, 2007 1 commit
    • simonpj@microsoft.com's avatar
      Fix several bugs related to finding free variables · 8ffdb8ee
      simonpj@microsoft.com authored
      Now that coercion variables mention types, a type-lambda binder can
      have free variables.  This patch adjusts the free-variable finder
      to take account of this, by treating Ids and TyVars more uniformly.
      
      In addition, I fixed a bug in the specialiser that was missing a 
      free type variable in a binder.  And a bug in tyVarsOfInst that
      was missing the type variables in the kinds of the quantified tyvars.
      8ffdb8ee
  10. 11 Dec, 2006 2 commits
  11. 24 Nov, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Fix constraint handling for lazy patterns · 36d207aa
      simonpj@microsoft.com authored
      Lazy patterns are quite tricky!  Consider
      	f ~(C x) = 3
      Can the Num constraint from the 3 be discharged by a Num dictionary
      bound by the pattern?  Definitely not!  
      
      See Note [Hopping the LIE in lazy patterns] in TcPat
      
      The type checker wasn't ensuring this, and that was causing all
      manner of strange things to happen.  It actually manifested as a
      strictness bug reported by Sven Panne.
      
      I've added his test case as tcrun040.
      36d207aa
  12. 22 Nov, 2006 1 commit
  13. 10 Nov, 2006 1 commit
  14. 13 Oct, 2006 1 commit
  15. 11 Oct, 2006 2 commits
  16. 05 Oct, 2006 1 commit
  17. 29 Sep, 2006 1 commit
  18. 23 Sep, 2006 1 commit
  19. 22 Sep, 2006 1 commit
  20. 20 Sep, 2006 5 commits
    • chak@cse.unsw.edu.au.'s avatar
      Adapt TcFix imports · 08093c69
      chak@cse.unsw.edu.au. authored
      Tue Sep 19 14:11:55 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
        * Adapt TcFix imports
      08093c69
    • chak@cse.unsw.edu.au.'s avatar
      Indexed newtypes · 27897431
      chak@cse.unsw.edu.au. authored
      Mon Sep 18 19:24:27 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
        * Indexed newtypes
        Thu Aug 31 22:09:21 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
          * Indexed newtypes
          - This patch makes indexed newtypes work
          - Only lightly tested
          - We need to distinguish between open and closed newtypes in a number of 
            places, because looking through newtypes doesn't work easily for open ones.
      27897431
    • chak@cse.unsw.edu.au.'s avatar
      Pattern matching of indexed data types · 6791ad22
      chak@cse.unsw.edu.au. authored
      Mon Sep 18 19:11:24 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
        * Pattern matching of indexed data types
        Thu Aug 24 14:17:44 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
          * Pattern matching of indexed data types
          - This patch is the last major puzzle piece to type check and desugar indexed 
            data types (both toplevel and associated with a class).
          - However, it needs more testing - esp wrt to accumlating CoPats - and some 
            static sanity checks for data instance declarations are still missing.
          - There are now two detailed notes in MkIds and TcPat on how the worker/wrapper
            and coercion story for indexed data types works.
      6791ad22
    • chak@cse.unsw.edu.au.'s avatar
      Complete the evidence generation for GADTs · 15cb792d
      chak@cse.unsw.edu.au. authored
      Mon Sep 18 14:43:22 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
        * Complete the evidence generation for GADTs
        Sat Aug  5 21:39:51 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
          * Complete the evidence generation for GADTs
          Thu Jul 13 17:18:07 EDT 2006  simonpj@microsoft.com
            
            This patch completes FC evidence generation for GADTs.
            
            It doesn't work properly yet, because part of the compiler thinks
            	(t1 :=: t2) => t3
            is represented with FunTy/PredTy, while the rest thinks it's represented
            using ForAllTy.  Once that's done things should start to work.
      15cb792d
    • chak@cse.unsw.edu.au.'s avatar
      Massive patch for the first months work adding System FC to GHC #34 · 3e83dfb2
      chak@cse.unsw.edu.au. authored
      Fri Sep 15 18:56:58 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
        * Massive patch for the first months work adding System FC to GHC #34
        Fri Aug  4 18:20:57 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
          * Massive patch for the first months work adding System FC to GHC #34
          
          Broken up massive patch -=chak
          Original log message:  
          This is (sadly) all done in one patch to avoid Darcs bugs.
          It's not complete work... more FC stuff to come.  A compiler
          using just this patch will fail dismally.
      3e83dfb2
  21. 08 Sep, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Catch errors in pattern matching for unboxed tuples · 4f2e93bc
      simonpj@microsoft.com authored
      When fiddling with pattern-matching for unboxed tuples, I'd messed up
      the slightly-tricky tests for pattern matching on unboxed tuples, notably
      	case (# foo, bar #) of r -> ...r...
      
      The fix is in TcPat, and test are tcfail115, tcfail120, and tc209
      4f2e93bc
  22. 07 Sep, 2006 1 commit
  23. 08 Aug, 2006 1 commit
  24. 04 Aug, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Do pre-subsumption in the main subsumption check · af20907a
      simonpj@microsoft.com authored
      This patch improves the subsumption check (in TcUnify.tc_sub) so that
      it does pre-subsumption first.  The key code is in the case with
      guard (isSigmaTy actual_ty); note the new call to preSubType.
      
      Shorn of details, the question is this.  Should this hold?
      
      	forall a. a->a   <=   Int -> (forall b. Int)
      
      Really, it should; just instantiate 'a' to Int.  This is just what
      the pre-subsumption phase (which used in function applications),
      will do.
      
      I did a bit of refactoring to achieve this.
      
      Fixes Trac #821.  Test tc205 tests.
      af20907a
  25. 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.
      0065d5ab
  26. 07 Feb, 2006 1 commit
  27. 03 Feb, 2006 1 commit
  28. 02 Feb, 2006 2 commits
  29. 31 Jan, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Fix TcUnify.subFunTys in AppTy case · c362e216
      simonpj@microsoft.com authored
      subFunTys wasn't dealing correctly with the case where the type
      to be split was of form (a ty1), where a is a type variable.
      
      This shows up when compiling 
      	Control.Arrow.Transformer.Stream
      in package arrows.
      
      This commit fixes it.
      
      c362e216
  30. 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) = ... 
      	      in 
         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.
      ac10f840
  31. 19 Dec, 2005 1 commit
  32. 12 Oct, 2005 1 commit