X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FMatch.lhs;h=a31494e0a879e2b78bbca96650a891f38dc5b23b;hp=641c2cace9193b7763a35fb40f0e5163c37100be;hb=49c98d143c382a1341e1046f5ca00819a25691ba;hpb=37507b3a4342773030ef538599363a5aff8b666a

diff --git a/compiler/deSugar/Match.lhs b/compiler/deSugar/Match.lhs
index 641c2ca..a31494e 100644
--- a/compiler/deSugar/Match.lhs
+++ b/compiler/deSugar/Match.lhs
@@ -1,40 +1,40 @@
 %
+% (c) The University of Glasgow 2006
 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 %
-\section[Main_match]{The @match@ function}
+
+The @match@ function
 
 \begin{code}
 module Match ( match, matchEquations, matchWrapper, matchSimply, matchSinglePat ) where
 
 #include "HsVersions.h"
 
-import DynFlags	( DynFlag(..), dopt )
+import DynFlags
 import HsSyn		
-import TcHsSyn		( mkVanillaTuplePat, hsPatType )
-import Check            ( check, ExhaustivePat )
+import TcHsSyn
+import Check
 import CoreSyn
-import Literal		( Literal )
-import CoreUtils	( bindNonRec, exprType )
+import Literal
+import CoreUtils
 import DsMonad
-import DsBinds		( dsLHsBinds, dsCoercion )
-import DsGRHSs		( dsGRHSs )
+import DsBinds
+import DsGRHSs
 import DsUtils
-import Id		( idName, idType, Id )
-import DataCon		( DataCon )
-import MatchCon		( matchConFamily )
-import MatchLit		( matchLiterals, matchNPlusKPats, matchNPats, 
-			  tidyLitPat, tidyNPat, hsLitKey, hsOverLitKey )
-import PrelInfo		( pAT_ERROR_ID )
-import TcType		( Type )
-import Type		( splitFunTysN, coreEqType )
-import TysWiredIn	( consDataCon, mkListTy, unitTy,
-			  tupleCon, parrFakeCon, mkPArrTy )
-import BasicTypes	( Boxity(..) )
-import ListSetOps	( equivClasses, runs )
-import SrcLoc		( unLoc, Located(..) )
-import Maybes		( isJust )
-import Util             ( lengthExceeds, notNull )
-import Name		( Name )
+import Id
+import DataCon
+import MatchCon
+import MatchLit
+import PrelInfo
+import TcType
+import Type
+import TysWiredIn
+import BasicTypes
+import ListSetOps
+import SrcLoc
+import Maybes
+import Util
+import Name
 import Outputable
 \end{code}
 
@@ -254,7 +254,7 @@ match :: [Id]		  -- Variables rep'ing the exprs we're matching with
       -> DsM MatchResult  -- Desugared result!
 
 match [] ty eqns
-  = ASSERT( not (null eqns) )
+  = ASSERT2( not (null eqns), ppr ty )
     returnDs (foldr1 combineMatchResults match_results)
   where
     match_results = [ ASSERT( null (eqn_pats eqn) ) 
@@ -305,7 +305,7 @@ matchCoercion :: [Id] -> Type -> [EquationInfo] -> DsM MatchResult
 matchCoercion (var:vars) ty (eqn1:eqns)
   = do	{ let CoPat co pat _ = firstPat eqn1
 	; var' <- newUniqueId (idName var) (hsPatType pat)
-	; match_result <- match (var:vars) ty (map shift (eqn1:eqns))
+	; match_result <- match (var':vars) ty (map shift (eqn1:eqns))
 	; rhs <- dsCoercion co (return (Var var))
 	; return (mkCoLetMatchResult (NonRec var' rhs) match_result) }
   where
@@ -392,7 +392,7 @@ tidy1 :: Id 			-- The Id being scrutinised
 
 tidy1 v (ParPat pat)      = tidy1 v (unLoc pat) 
 tidy1 v (SigPatOut pat _) = tidy1 v (unLoc pat) 
-tidy1 v (WildPat ty)      = returnDs (idWrapper, WildPat ty)
+tidy1 v (WildPat ty)      = returnDs (idDsWrapper, WildPat ty)
 
 	-- case v of { x -> mr[] }
 	-- = case v of { _ -> let x=v in mr[] }
@@ -427,7 +427,7 @@ tidy1 v (LazyPat pat)
 	; returnDs (mkDsLets sel_binds, WildPat (idType v)) }
 
 tidy1 v (ListPat pats ty)
-  = returnDs (idWrapper, unLoc list_ConPat)
+  = returnDs (idDsWrapper, unLoc list_ConPat)
   where
     list_ty     = mkListTy ty
     list_ConPat = foldr (\ x y -> mkPrefixConPat consDataCon [x, y] list_ty)
@@ -437,13 +437,13 @@ tidy1 v (ListPat pats ty)
 -- Introduce fake parallel array constructors to be able to handle parallel
 -- arrays with the existing machinery for constructor pattern
 tidy1 v (PArrPat pats ty)
-  = returnDs (idWrapper, unLoc parrConPat)
+  = returnDs (idDsWrapper, unLoc parrConPat)
   where
     arity      = length pats
     parrConPat = mkPrefixConPat (parrFakeCon arity) pats (mkPArrTy ty)
 
 tidy1 v (TuplePat pats boxity ty)
-  = returnDs (idWrapper, unLoc tuple_ConPat)
+  = returnDs (idDsWrapper, unLoc tuple_ConPat)
   where
     arity = length pats
     tuple_ConPat = mkPrefixConPat (tupleCon boxity arity) pats ty
@@ -459,16 +459,16 @@ tidy1 v (DictPat dicts methods)
 
 -- LitPats: we *might* be able to replace these w/ a simpler form
 tidy1 v (LitPat lit)
-  = returnDs (idWrapper, tidyLitPat lit)
+  = returnDs (idDsWrapper, tidyLitPat lit)
 
 -- NPats: we *might* be able to replace these w/ a simpler form
 tidy1 v (NPat lit mb_neg eq lit_ty)
-  = returnDs (idWrapper, tidyNPat lit mb_neg eq lit_ty)
+  = returnDs (idDsWrapper, tidyNPat lit mb_neg eq lit_ty)
 
 -- Everything else goes through unchanged...
 
 tidy1 v non_interesting_pat
-  = returnDs (idWrapper, non_interesting_pat)
+  = returnDs (idDsWrapper, non_interesting_pat)
 \end{code}
 
 \noindent
@@ -715,6 +715,9 @@ data PatGroup
 
 
 groupEquations :: [EquationInfo] -> [[(PatGroup, EquationInfo)]]
+-- If the result is of form [g1, g2, g3], 
+-- (a) all the (pg,eq) pairs in g1 have the same pg
+-- (b) none of the gi are empty
 groupEquations eqns
   = runs same_gp [(patGroup (firstPat eqn), eqn) | eqn <- eqns]
   where
@@ -745,6 +748,10 @@ sameGroup (PgN l1)   (PgN l2)   = True		-- Needs conditionals
 sameGroup (PgNpK l1) (PgNpK l2) = l1==l2	-- Order is significant
 						-- See Note [Order of n+k]
 sameGroup (PgCo	t1)  (PgCo t2)  = t1 `coreEqType` t2
+	-- CoPats are in the same goup only if the type of the
+	-- enclosed pattern is the same. The patterns outside the CoPat
+	-- always have the same type, so this boils down to saying that
+	-- the two coercions are identical.
 sameGroup _          _          = False
  
 patGroup :: Pat Id -> PatGroup