X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FdeSugar%2FDsGRHSs.lhs;h=33f86edcf90b3c69bcd101f408f35d08b133865a;hb=63539f9d057f2143ea395da99584bc898b321c9b;hp=b14e264d4005231425a57a4204085ef9a0fa54f6;hpb=861e836ed0cc1aa45932ecb3470967964440a0ef;p=ghc-hetmet.git

diff --git a/ghc/compiler/deSugar/DsGRHSs.lhs b/ghc/compiler/deSugar/DsGRHSs.lhs
index b14e264..33f86ed 100644
--- a/ghc/compiler/deSugar/DsGRHSs.lhs
+++ b/ghc/compiler/deSugar/DsGRHSs.lhs
@@ -8,18 +8,23 @@ module DsGRHSs ( dsGuarded, dsGRHSs ) where
 
 #include "HsVersions.h"
 
-import {-# SOURCE #-} DsExpr  ( dsExpr, dsLet )
+import {-# SOURCE #-} DsExpr  ( dsLExpr, dsLocalBinds )
 import {-# SOURCE #-} Match   ( matchSinglePat )
 
-import HsSyn		( Stmt(..), HsExpr(..), GRHSs(..), GRHS(..) )
-import TcHsSyn		( TypecheckedGRHSs, TypecheckedPat, TypecheckedStmt )
+import HsSyn		( Stmt(..), HsExpr(..), GRHSs(..), GRHS(..), 
+			  LHsExpr, HsMatchContext(..), Pat(..) )
 import CoreSyn		( CoreExpr )
+import Var		( Id )
 import Type		( Type )
 
 import DsMonad
 import DsUtils
+import Unique		( Uniquable(..) )
 import PrelInfo		( nON_EXHAUSTIVE_GUARDS_ERROR_ID )
-import PrelNames	( otherwiseIdKey, trueDataConKey, hasKey )
+import TysWiredIn	( trueDataConId )
+import PrelNames	( otherwiseIdKey, hasKey )
+import Name		( Name )
+import SrcLoc		( unLoc, Located(..) )
 \end{code}
 
 @dsGuarded@ is used for both @case@ expressions and pattern bindings.
@@ -34,32 +39,33 @@ producing an expression with a runtime error in the corner if
 necessary.  The type argument gives the type of the @ei@.
 
 \begin{code}
-dsGuarded :: TypecheckedGRHSs -> DsM CoreExpr
+dsGuarded :: GRHSs Id -> Type -> DsM CoreExpr
 
-dsGuarded grhss
-  = dsGRHSs PatBindMatch [] grhss 				`thenDs` \ (err_ty, match_result) ->
-    mkErrorAppDs nON_EXHAUSTIVE_GUARDS_ERROR_ID err_ty ""	`thenDs` \ error_expr ->
+dsGuarded grhss rhs_ty
+  = dsGRHSs PatBindRhs [] grhss rhs_ty 				`thenDs` \ match_result ->
+    mkErrorAppDs nON_EXHAUSTIVE_GUARDS_ERROR_ID rhs_ty ""	`thenDs` \ error_expr ->
     extractMatchResult match_result error_expr
 \end{code}
 
 In contrast, @dsGRHSs@ produces a @MatchResult@.
 
 \begin{code}
-dsGRHSs :: DsMatchKind -> [TypecheckedPat]	-- These are to build a MatchContext from
-	-> TypecheckedGRHSs			-- Guarded RHSs
-	-> DsM (Type, MatchResult)
+dsGRHSs :: HsMatchContext Name -> [Pat Id]	-- These are to build a MatchContext from
+	-> GRHSs Id				-- Guarded RHSs
+	-> Type					-- Type of RHS
+	-> DsM MatchResult
 
-dsGRHSs kind pats (GRHSs grhss binds (Just ty))
-  = mapDs (dsGRHS kind pats) grhss		`thenDs` \ match_results ->
+dsGRHSs hs_ctx pats (GRHSs grhss binds) rhs_ty
+  = mappM (dsGRHS hs_ctx pats rhs_ty) grhss	`thenDs` \ match_results ->
     let 
 	match_result1 = foldr1 combineMatchResults match_results
-	match_result2 = adjustMatchResultDs (dsLet binds) match_result1
+	match_result2 = adjustMatchResultDs (dsLocalBinds binds) match_result1
 		-- NB: nested dsLet inside matchResult
     in
-    returnDs (ty, match_result2)
+    returnDs match_result2
 
-dsGRHS kind pats (GRHS guard locn)
-  = matchGuard guard (DsMatchContext kind pats locn)
+dsGRHS hs_ctx pats rhs_ty (L loc (GRHS guards rhs))
+  = matchGuards (map unLoc guards) hs_ctx rhs rhs_ty
 \end{code}
 
 
@@ -70,34 +76,45 @@ dsGRHS kind pats (GRHS guard locn)
 %************************************************************************
 
 \begin{code}
-matchGuard :: [TypecheckedStmt] 	-- Guard
-           -> DsMatchContext            -- Context
-	   -> DsM MatchResult
+matchGuards :: [Stmt Id] 		-- Guard
+            -> HsMatchContext Name	-- Context
+	    -> LHsExpr Id		-- RHS
+	    -> Type			-- Type of RHS of guard
+	    -> DsM MatchResult
 
-matchGuard (ExprStmt expr locn : should_be_null) ctx 
-  = putSrcLocDs locn (dsExpr expr) 	`thenDs` \ core_expr ->
-    returnDs (cantFailMatchResult core_expr)
+-- See comments with HsExpr.Stmt re what an ExprStmt means
+-- Here we must be in a guard context (not do-expression, nor list-comp)	
 
+matchGuards [] ctx rhs rhs_ty
+  = do	{ core_rhs <- dsLExpr rhs
+	; return (cantFailMatchResult core_rhs) }
+
+	-- ExprStmts must be guards
 	-- Turn an "otherwise" guard is a no-op
-matchGuard (GuardStmt (HsVar v) _ : stmts) ctx
+matchGuards (ExprStmt (L _ (HsVar v)) _ _ : stmts) ctx rhs rhs_ty
   |  v `hasKey` otherwiseIdKey
-  || v `hasKey` trueDataConKey
-  = matchGuard stmts ctx
-
-matchGuard (GuardStmt expr locn : stmts) ctx
-  = matchGuard stmts ctx 		`thenDs` \ match_result ->
-    putSrcLocDs locn (dsExpr expr)	`thenDs` \ pred_expr ->
+  || v `hasKey` getUnique trueDataConId	
+	-- trueDataConId doesn't have the same 
+	-- unique as trueDataCon
+  = matchGuards stmts ctx rhs rhs_ty
+
+matchGuards (ExprStmt expr _ _ : stmts) ctx rhs rhs_ty
+  = matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
+    dsLExpr expr			`thenDs` \ pred_expr ->
     returnDs (mkGuardedMatchResult pred_expr match_result)
 
-matchGuard (LetStmt binds : stmts) ctx
-  = matchGuard stmts ctx 	`thenDs` \ match_result ->
-    returnDs (adjustMatchResultDs (dsLet binds) match_result)
+matchGuards (LetStmt binds : stmts) ctx rhs rhs_ty
+  = matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
+    returnDs (adjustMatchResultDs (dsLocalBinds binds) match_result)
 	-- NB the dsLet occurs inside the match_result
-
-matchGuard (BindStmt pat rhs locn : stmts) ctx
-  = matchGuard stmts ctx 		`thenDs` \ match_result ->
-    putSrcLocDs locn (dsExpr rhs)	`thenDs` \ core_rhs ->
-    matchSinglePat core_rhs ctx pat match_result
+	-- Reason: dsLet takes the body expression as its argument
+	--	   so we can't desugar the bindings without the
+	--	   body expression in hand
+
+matchGuards (BindStmt pat bind_rhs _ _ : stmts) ctx rhs rhs_ty
+  = matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
+    dsLExpr bind_rhs			`thenDs` \ core_rhs ->
+    matchSinglePat core_rhs ctx pat rhs_ty match_result
 \end{code}
 
 Should {\em fail} if @e@ returns @D@