1. 25 Apr, 2007 1 commit
  2. 22 Apr, 2007 1 commit
    • simonpj@microsoft.com's avatar
      Fix corner case of useless constraint in SPECIALISE pragma · e5ca7e6e
      simonpj@microsoft.com authored
      	MERGE TO STABLE
      
      This patch fixes Trac #1287.  
      
      The problem is described in Note [Unused spec binders] in DsBinds.
      
      At the same time I realised that the error messages in DsBinds.dsPrag
      were being given the location of the *binding* not the *pragma*.
      So I've fixed that too.
      e5ca7e6e
  3. 11 Dec, 2006 1 commit
    • simonpj@microsoft.com's avatar
      More refactoring of constraint simplification · 2423c249
      simonpj@microsoft.com authored
      This patch fixes several bugs in the handling of impliciation
      constraints, thereby fixing several regression-suite failures.
      
      On the way I managed to further simplify the code in TcSimplify;
      the extra lines are comments.
      2423c249
  4. 10 Nov, 2006 2 commits
  5. 24 Oct, 2006 1 commit
    • andy@galois.com's avatar
      Haskell Program Coverage · d5934bbb
      andy@galois.com authored
      This large checkin is the new ghc version of Haskell
      Program Coverage, an expression-level coverage tool for Haskell.
      
      Parts:
      
       - Hpc.[ch] - small runtime support for Hpc; reading/writing *.tix files.
       - Coverage.lhs - Annotates the HsSyn with coverage tickboxes.
        - New Note's in Core,
            - TickBox      -- ticked on entry to sub-expression
            - BinaryTickBox  -- ticked on exit to sub-expression, depending
      	       	     -- on the boolean result.
      
        - New Stg level TickBox (no BinaryTickBoxes, though) 
      
      You can run the coverage tool with -fhpc at compile time. 
      Main must be compiled with -fhpc. 
      				      
      d5934bbb
  6. 11 Oct, 2006 2 commits
  7. 03 Oct, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Fix scoped type variables for expression type signatures · 9da46390
      simonpj@microsoft.com authored
      I had forgotten to bring scoped type variables into scope at an expression
      type signature, such as
      	e :: forall s. <type>
      where 's' should scope over the expression e.
      
      Like everything to do with scoped type variables, fixing this took an 
      unreasonable amount of work.  I'm sure there must be a better way to 
      achitect this!
      
      I updated the user manual too.
      
      A test is tc213.
      
      It would be good to push this into 6.6.1
      9da46390
  8. 29 Sep, 2006 1 commit
  9. 20 Sep, 2006 2 commits
    • 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
  10. 18 Sep, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Ensure that only zonked poly_ids are passed to tcSpecPrag · 40f5a075
      simonpj@microsoft.com authored
      This is a long-standing bug really (Trac #900).  The poly_id passed
      to tcSpecPrag should be zonked, else it calls tcSubExp with a non-zonked
      type; but that contradicts the latter's invariant.
      
      I ended up doing a bit of refactoring too.  The extra lines are 
      comments I think; the code line count is reduced.
      
      Test is tc212.hs
      40f5a075
  11. 06 Sep, 2006 1 commit
  12. 05 Sep, 2006 1 commit
    • simonpj@microsoft.com's avatar
      Fix dependency analysis (notably bindInstsOfLocalFuns) in TcBinds · c18587da
      simonpj@microsoft.com authored
      GHC 6.5 does enhanced dependency analysis for recursive bindings, to 
      maximise polymorphism based on type signatures.  (See Mark Jones's
      THIH paper.)  
      
      I didn't do the bindInstsOfLocalFuns part correctly though, and jhc
      showed up the bug.  (It only matters when you have a recursive group
      of two or more functions with a type signature, not at top level, which
      is why it hasn't shown up till now.) 
      
      Test is tc207.hs
      
      c18587da
  13. 11 Aug, 2006 2 commits
  14. 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
      binding.)  
      
      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.
      10ffe4f7
  15. 21 Jun, 2006 1 commit
  16. 12 Jun, 2006 1 commit
  17. 14 Apr, 2006 1 commit
  18. 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
  19. 02 Mar, 2006 1 commit
  20. 03 Feb, 2006 1 commit
  21. 01 Feb, 2006 1 commit
  22. 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.
      eb57096f
  23. 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
  24. 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.
      958924a2
  25. 11 Aug, 2005 1 commit
  26. 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
  27. 25 Jul, 2005 1 commit
  28. 22 Jul, 2005 1 commit
  29. 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
  30. 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
  31. 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
  32. 03 May, 2005 1 commit
  33. 15 Apr, 2005 1 commit
  34. 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
  35. 17 Mar, 2005 1 commit
  36. 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