[project @ 2004-09-30 10:35:15 by simonpj]

------------------------------------
	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).

1 files changed, 7 insertions, 8 deletions

diff --git a/ghc/compiler/rename/RnEnv.lhs b/ghc/compiler/rename/RnEnv.lhs
index c9e48cbfca..821f6a97a4 100644
--- a/ghc/compiler/rename/RnEnv.lhs
+++ b/ghc/compiler/rename/RnEnv.lhs
@@ -42,14 +42,13 @@ import RdrName		( RdrName, rdrNameModule, rdrNameOcc, isQual, isUnqual, isOrig,
 			  isLocalGRE, extendLocalRdrEnv, elemLocalRdrEnv, lookupLocalRdrEnv,
 			  Provenance(..), pprNameProvenance, ImportSpec(..) 
 			)
-import HsTypes		( hsTyVarName, replaceTyVarName )
+import HsTypes		( replaceTyVarName )
 import HscTypes		( availNames, ModIface(..), FixItem(..), lookupFixity )
 import TcRnMonad
 import Name		( Name, nameIsLocalOrFrom, mkInternalName, isInternalName,
 			  nameSrcLoc, nameOccName, nameModuleName, nameParent )
 import NameSet
-import OccName		( tcName, isDataOcc, occNameFlavour, reportIfUnused,
-			  isVarOcc )
+import OccName		( tcName, isDataOcc, occNameFlavour, reportIfUnused )
 import Module		( Module, ModuleName, moduleName, mkHomeModule )
 import PrelNames	( mkUnboundName, rOOT_MAIN_Name, iNTERACTIVE, consDataConKey, hasKey )
 import UniqSupply
@@ -130,7 +129,7 @@ lookupLocatedBndrRn :: Located RdrName -> RnM (Located Name)
 lookupLocatedBndrRn = wrapLocM lookupBndrRn
 
 lookupBndrRn :: RdrName -> RnM Name
--- NOTE: assumes that the SrcSpan of the binder has already been addSrcSpan'd
+-- NOTE: assumes that the SrcSpan of the binder has already been setSrcSpan'd
 lookupBndrRn rdr_name
   = getLocalRdrEnv		`thenM` \ local_env ->
     case lookupLocalRdrEnv local_env rdr_name of 
@@ -590,7 +589,7 @@ bindTyVarsRn :: SDoc -> [LHsTyVarBndr RdrName]
 	      -> RnM a
 bindTyVarsRn doc_str tyvar_names enclosed_scope
   = let
-	located_tyvars = [L loc (hsTyVarName tv) | L loc tv <- tyvar_names] 
+	located_tyvars = hsLTyVarLocNames tyvar_names
     in
     bindLocatedLocalsRn doc_str located_tyvars	$ \ names ->
     enclosed_scope (zipWith replace tyvar_names names)
@@ -641,7 +640,7 @@ checkShadowing doc_str loc_rdr_names
       check_shadow (L loc rdr_name)
 	|  rdr_name `elemLocalRdrEnv` local_env 
  	|| not (null (lookupGRE_RdrName rdr_name global_env ))
-	= addSrcSpan loc $ addWarn (shadowedNameWarn doc_str rdr_name)
+	= setSrcSpan loc $ addWarn (shadowedNameWarn doc_str rdr_name)
         | otherwise = returnM ()
     in
     mappM_ check_shadow loc_rdr_names
@@ -675,7 +674,7 @@ warnUnusedModules :: [(ModuleName,SrcSpan)] -> RnM ()
 warnUnusedModules mods
   = ifOptM Opt_WarnUnusedImports (mappM_ bleat mods)
   where
-    bleat (mod,loc) = addSrcSpan loc $ addWarn (mk_warn mod)
+    bleat (mod,loc) = setSrcSpan loc $ addWarn (mk_warn mod)
     mk_warn m = vcat [ptext SLIT("Module") <+> quotes (ppr m) <+> 
 			 text "is imported, but nothing from it is used",
 			 parens (ptext SLIT("except perhaps instances visible in") <+>
@@ -749,7 +748,7 @@ badOrigBinding name
 	-- The rdrNameOcc is because we don't want to print Prelude.(,)
 
 dupNamesErr descriptor (L loc name : dup_things)
-  = addSrcSpan loc $
+  = setSrcSpan loc $
     addErr ((ptext SLIT("Conflicting definitions for") <+> quotes (ppr name))
 	      $$ 
 	      descriptor)