1. 27 Jun, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-06-27 12:59:52 by simonpj] · a9ae952e
      simonpj authored
      MERGE TO STABLE
      
      Fix a typechecker bug, which made the typechecker loop under certain
      circumstances, notably when we have
      	type Foo a = a
      and try to unify
      	b :=: Foo b
      
      typecheck/should_compile/tc195 tests this case now.
      a9ae952e
  2. 31 Jan, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-01-31 13:25:33 by simonpj] · f25b9225
      simonpj authored
      ---------------------------
      	Types and evaluated-ness in
      	  CoreTidy and CorePrep
      	---------------------------
      
      This commmit fixes two problems.
      
      1.  DataToTagOp requires its argument to be evaluated, otherwise it silently
          gives the wrong answer.  This was not happening because we had
      	case (tag2Enum x) of y -> ...(dataToTag y)...
          and the tag2Enum was being inlined (it's non-speculative), giving
      	...(dataToTag (tag2Enum x))...
      
          Rather than relying on a somewhat-delicate global invariant, CorePrep
          now establishes the invariant that DataToTagOp's argument is evaluated.
          It does so by putting up-to-date is-evaluated information into each
          binder's UnfoldingInfo; not a full unfolding, just the (OtherCon [])
          for evaluated binders.
      
          Then there's a special case for DataToTag where applications are dealt with.
      
          Finally, we make DataToTagOp strict, which it really is.
      
      
      2.  CoreTidy now does GADT refinement as it goes. This is important to ensure that
          each variable occurrence has informative type information, which in turn is
          essential to make exprType work (otherwise it can simply crash).
          [This happened in test gadt/tdpe]
      
          CorePrep has the same problem, but the solution is a little different:
          when looking up in the cloning environment, use the type at the occurrence
          site if we're inside a GADT.  It might be cleaner to use the same story as
          CoreTidy, but then we'd need to keep an in-scope set for type variables.
          No big deal either way.
      f25b9225
  3. 05 Jan, 2005 1 commit
    • simonpj's avatar
      [project @ 2005-01-05 15:28:39 by simonpj] · 19da321b
      simonpj authored
      ------------------------
                GADTs and unification
        	------------------------
      
      1. Adjustment to typechecking of pattern matching the call to
         gadtRefineTys in TcPat.  Now wobbly types are treated as wild
         cards in the unification process.
      
      2. Add the WildCard possibility to the BindFlag in types/Unify.lhs
      
      3. Some related refactoring of tcMatchTys etc.
      19da321b
  4. 30 Dec, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-12-30 22:14:59 by simonpj] · 7f05f109
      simonpj authored
      Fix to the pre-Xmas simplifier changes, which should make 
      everything work again.  I'd forgotten to attend to this
      corner.  Still not properly tested I fear.
      
      Also remove dead code from SimplEnv, and simplify the remainder (hooray).
      7f05f109
  5. 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
  6. 21 Dec, 2004 2 commits
    • simonpj's avatar
      [project @ 2004-12-21 12:22:22 by simonpj] · 79a8b87c
      simonpj authored
      ---------------------------------
           Improve handling of lexically scoped type variables
      	---------------------------------
      
      If we have
      
      	f :: T a -> a
      	f (x :: T b) = ...
      
      then the lexically scoped variable 'b' should refer to the rigid
      type variable 'a', without any intervening wobbliness.  Previously
      the in-scope type variables were always mutable TyVars, which were
      instantatiated to point to the type they were bound to; but since
      the advent of GADTs the intervening mutable type variable is a bad
      thing.
      
      Hence
        * In the type environment, ATyVar now carries a type
        * The call to refineTyVars in tc_pat on SigPatIn
          finds the types by matching
        * Then tcExtendTyVarEnv3 extends the type envt appropriately
      
      Rater a lot of huff and puff, but it's quite natural for ATyVar
      to contain a type.
      
      Various other small nomenclature changes along the way.
      79a8b87c
    • simonpj's avatar
      [project @ 2004-12-21 12:09:55 by simonpj] · 5fa56a91
      simonpj authored
      Add missing NoteTy cases to unify_
      5fa56a91
  7. 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
  8. 01 Oct, 2004 1 commit
    • simonpj's avatar
      [project @ 2004-10-01 13:42:04 by simonpj] · 837824d2
      simonpj authored
      ------------------------------------
      	Simplify the treatment of newtypes
      	Complete hi-boot file consistency checking
      	------------------------------------
      
      In the representation of types, newtypes used to have a special constructor
      all to themselves, very like TyConApp, called NewTcApp.    The trouble is
      that means we have to *know* when a newtype is a newtype, and in an hi-boot
      context we may not -- the data type might be declared as
      	data T
      in the hi-boot file, but as
      	newtype T = ...
      in the source file.  In GHCi, which accumulates stuff from multiple compiles,
      this makes a difference.
      
      So I've nuked NewTcApp.  Newtypes are represented using TyConApps again. This
      turned out to reduce the total amount of code, and simplify the Type data type,
      which is all to the good.
      
      
      This commit also fixes a few things in the hi-boot consistency checking
      stuff.
      837824d2
  9. 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
  10. 25 Jun, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-06-25 08:09:57 by simonpj] · d069cec2
      simonpj authored
      ----------------
      	Squash newtypes
      	----------------
      
      This commit squashes newtypes and their coerces, from the typechecker
      onwards.  The original idea was that the coerces would not get in the
      way of optimising transformations, but despite much effort they continue
      to do so.   There's no very good reason to retain newtype information
      beyond the typechecker, so now we don't.
      
      Main points:
      
      * The post-typechecker suite of Type-manipulating functions is in
      types/Type.lhs, as before.   But now there's a new suite in types/TcType.lhs.
      The difference is that in the former, newtype are transparent, while in
      the latter they are opaque.  The typechecker should only import TcType,
      not Type.
      
      * The operations in TcType are all non-monadic, and most of them start with
      "tc" (e.g. tcSplitTyConApp).  All the monadic operations (used exclusively
      by the typechecker) are in a new module, typecheck/TcMType.lhs
      
      * I've grouped newtypes with predicate types, thus:
      	data Type = TyVarTy Tyvar | ....
      		  | SourceTy SourceType
      
      	data SourceType = NType TyCon [Type]
      			| ClassP Class [Type]
      			| IParam Type
      
      [SourceType was called PredType.]  This is a little wierd in some ways,
      because NTypes can't occur in qualified types.   However, the idea is that
      a SourceType is a type that is opaque to the type checker, but transparent
      to the rest of the compiler, and newtypes fit that as do implicit parameters
      and dictionaries.
      
      * Recursive newtypes still retain their coreces, exactly as before. If
      they were transparent we'd get a recursive type, and that would make
      various bits of the compiler diverge (e.g. things which do type comparison).
      
      * I've removed types/Unify.lhs (non-monadic type unifier and matcher),
      merging it into TcType.
      
      Ditto typecheck/TcUnify.lhs (monadic unifier), merging it into TcMType.
      d069cec2
  11. 30 Jan, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-01-30 09:53:11 by simonpj] · ade2eac4
      simonpj authored
      More on functional dependencies
      
      My last commit allowed this:
      
      	instance C a b => C [a] [b] where ...
      
      if we have
      
      	class C a b | a -> b
      
      This commit completes the change, by making the 
      improvement stages improve only the 'shape' of the second
      argument of C.  
      
      I also had to change the iteration in TcSimplify -- see
      the comments in TcSimplify.inferLoop.
      ade2eac4
  12. 25 Jan, 2001 1 commit
    • simonpj's avatar
      [project @ 2001-01-25 17:54:24 by simonpj] · 4e342297
      simonpj authored
      ------------------------------------
      	   Mainly FunDeps (23 Jan 01)
      	------------------------------------
      
      This commit re-engineers the handling of functional dependencies.
      A functional dependency is no longer an Inst; instead, the necessary
      dependencies are snaffled out of their Class when necessary.
      
      As part of this exercise I found that I had to re-work how to do generalisation
      in a binding group.  There is rather exhaustive documentation on the new Plan
      at the top of TcSimplify.
      
      	******************
      	WARNING: I have compiled all the libraries with this new compiler
      		 and all looks well, but I have not run many programs.
      		 Things may break.  Let me know if so.
      	******************
      
      The main changes are these:
      
      1.  typecheck/TcBinds and TcSimplify have a lot of changes due to the
          new generalisation and context reduction story.  There are extensive
          comments at the start of TcSimplify
      
      2.  typecheck/TcImprove is removed altogether.  Instead, improvement is
          interleaved with context reduction (until a fixpoint is reached).
          All this is done in TcSimplify.
      
      3.  types/FunDeps has new exports
      	* 'improve' does improvement, returning a list of equations
      	* 'grow' and 'oclose' close a list of type variables wrt a set of
      	  PredTypes, but in slightly different ways.  Comments in file.
      
      4.  I improved the way in which we check that main::IO t.  It's tidier now.
      
      In addition
      
      *   typecheck/TcMatches:
      	a) Tidy up, introducing a common function tcCheckExistentialPat
      
      	b) Improve the typechecking of parallel list comprehensions,
      	   which wasn't quite right before.  (see comments with tcStmts)
      
      	WARNING: (b) is untested!  Jeff, you might want to check.
      
      *   Numerous other incidental changes in the typechecker
      
      *   Manuel found that rules don't fire well when you have partial applications
          from overloading.  For example, we may get
      
      	f a (d::Ord a) = let m_g = g a d
      			 in
      			 \y :: a -> ...(m_g (h y))...
      
          The 'method' m_g doesn't get inlined because (g a d) might be a redex.
          Yet a rule that looks like
      		g a d (h y) = ...
          won't fire because that doesn't show up.  One way out would be to make
          the rule matcher a bit less paranoid about duplicating work, but instead
          I've added a flag
      			-fno-method-sharing
          which controls whether we generate things like m_g in the first place.
          It's not clear that they are a win in the first place.
      
          The flag is actually consulted in Inst.tcInstId
      4e342297
  13. 07 Nov, 2000 1 commit
  14. 23 Oct, 2000 1 commit
  15. 14 Jul, 2000 1 commit
    • simonpj's avatar
      [project @ 2000-07-14 08:17:36 by simonpj] · 77a8c0db
      simonpj authored
      This commit completely re-does the kind-inference mechanism.
      Previously it was inter-wound with type inference, but that was
      always hard to understand, and it finally broke when we started
      checking for ambiguity when type-checking a type signature (details
      irrelevant).
      
      So now kind inference is more clearly separated, so that it never
      takes place at the same time as type inference.  The biggest change
      is in TcTyClsDecls, which does the kind inference for a group of
      type and class declarations.  It now contains comments to explain
      how it all works.
      
      There are also comments in TypeRep which describes the slightly
      tricky way in which we deal with the fact that kind 'type' (written
      '*') actually has 'boxed type' and 'unboxed type' as sub-kinds.
      The whole thing is a bit of a hack, because we don't really have 
      sub-kinding, but it's less of a hack than before.
      
      A lot of general tidying up happened at the same time.
      In particular, I removed some dead code here and there
      77a8c0db
  16. 11 Jul, 2000 1 commit
  17. 27 Mar, 2000 1 commit
    • simonpj's avatar
      [project @ 2000-03-27 16:22:09 by simonpj] · 783e505e
      simonpj authored
      Fix a bug in import listing in interface files that meant we lost track of
      interface files.  This fixes the problem that led Sven to add lots of
      import PprType() decls.  I've removed them all again!
      783e505e
  18. 15 Jul, 1999 1 commit
    • keithw's avatar
      [project @ 1999-07-15 14:08:03 by keithw] · 9d787ef5
      keithw authored
      This commit makes a start at implementing polymorphic usage
      annotations.
      
      * The module Type has now been split into TypeRep, containing the
        representation Type(..) and other information for `friends' only,
        and Type, providing the public interface to Type.  Due to a bug in
        the interface-file slurping prior to ghc-4.04, {-# SOURCE #-}
        dependencies must unfortunately still refer to TypeRep even though
        they are not friends.
      
      * Unfoldings in interface files now print as __U instead of __u.
        UpdateInfo now prints as __UA instead of __U.
      
      * A new sort of variables, UVar, in their own namespace, uvName, has
        been introduced for usage variables.
      
      * Usage binders __fuall uv have been introduced.  Usage annotations
        are now __u - ty (used once), __u ! ty (used possibly many times),
        __u uv ty (used uv times), where uv is a UVar.  __o and __m have
        gone.  All this still lives only in a TyNote, *for now* (but not for
        much longer).
      
      * Variance calculation for TyCons has moved from
        typecheck/TcTyClsDecls to types/Variance.
      
      * Usage annotation and inference are now done together in a single
        pass.  Provision has been made for inferring polymorphic usage
        annotations (with __fuall) but this has not yet been implemented.
        Watch this space!
      9d787ef5
  19. 18 May, 1999 1 commit
  20. 18 Dec, 1998 1 commit
    • simonpj's avatar
      [project @ 1998-12-18 17:40:31 by simonpj] · 7e602b0a
      simonpj authored
      Another big commit from Simon.  Actually, the last one
      didn't all go into the main trunk; because of a CVS glitch it
      ended up in the wrong branch.
      
      So this commit includes:
      
      * Scoped type variables
      * Warnings for unused variables should work now (they didn't before)
      * Simplifier improvements:
      	- Much better treatment of strict arguments
      	- Better treatment of bottoming Ids
      	- No need for w/w split for fns that are merely strict
      	- Fewer iterations needed, I hope
      * Less gratuitous renaming in interface files and abs C
      * OccName is a separate module, and is an abstract data type
      
      I think the whole Prelude and Exts libraries compile correctly.
      Something isn't quite right about typechecking existentials though.
      7e602b0a
  21. 02 Dec, 1998 1 commit