%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1994
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[DsGRHSs]{Matching guarded right-hand-sides (GRHSs)}
#include "HsVersions.h"
-import {-# SOURCE #-} DsExpr ( dsExpr )
-import {-# SOURCE #-} DsBinds ( dsBinds )
-import {-# SOURCE #-} Match ( matchExport )
+import {-# SOURCE #-} DsExpr ( dsExpr, dsLet )
+import {-# SOURCE #-} Match ( matchSinglePat )
-import HsSyn ( GRHSsAndBinds(..), GRHS(..),
- HsExpr(..), HsBinds, Stmt(..),
- HsLit, Match, Fixity, DoOrListComp, HsType, ArithSeqInfo
- )
+import HsSyn ( GRHSsAndBinds(..), Stmt(..), HsExpr(..), GRHS(..) )
import TcHsSyn ( TypecheckedGRHSsAndBinds, TypecheckedGRHS,
- TypecheckedPat, TypecheckedHsBinds,
- TypecheckedHsExpr, TypecheckedStmt
+ TypecheckedPat, TypecheckedStmt
)
-import CoreSyn ( CoreBinding, GenCoreBinding(..), CoreExpr, mkCoLetsAny )
+import CoreSyn ( CoreExpr, Bind(..) )
import DsMonad
import DsUtils
-import CoreUtils ( coreExprType, mkCoreIfThenElse )
import PrelVals ( nON_EXHAUSTIVE_GUARDS_ERROR_ID )
-import SrcLoc ( SrcLoc{-instance-} )
-import Type ( Type )
-import Unique ( Unique, otherwiseIdKey, trueDataConKey, Uniquable(..) )
+import Unique ( otherwiseIdKey, trueDataConKey, Uniquable(..) )
import Outputable
\end{code}
-> DsM CoreExpr
dsGuarded (GRHSsAndBindsOut grhss binds err_ty)
- = dsBinds False{-don't auto scc-} binds `thenDs` \ core_binds ->
- dsGRHSs err_ty PatBindMatch [] grhss `thenDs` \ (MatchResult can_it_fail _ core_grhss_fn) ->
- case can_it_fail of
- CantFail -> returnDs (mkCoLetsAny core_binds (core_grhss_fn (panic "It can't fail")))
- CanFail -> mkErrorAppDs nON_EXHAUSTIVE_GUARDS_ERROR_ID err_ty "" `thenDs` \ error_expr ->
- returnDs (mkCoLetsAny core_binds (core_grhss_fn error_expr))
+ = dsGRHSs PatBindMatch [] grhss `thenDs` \ match_result ->
+ mkErrorAppDs nON_EXHAUSTIVE_GUARDS_ERROR_ID err_ty "" `thenDs` \ error_expr ->
+ extractMatchResult match_result error_expr `thenDs` \ body ->
+ dsLet binds body
\end{code}
Desugar a list of (grhs, expr) pairs [grhs = guarded
the guards fail.
\begin{code}
-dsGRHSs :: Type -- Type of RHSs
- -> DsMatchKind -> [TypecheckedPat] -- These are to build a MatchContext from
+dsGRHSs :: DsMatchKind -> [TypecheckedPat] -- These are to build a MatchContext from
-> [TypecheckedGRHS] -- Guarded RHSs
-> DsM MatchResult
-dsGRHSs ty kind pats [grhs] = dsGRHS ty kind pats grhs
+dsGRHSs kind pats [grhs] = dsGRHS kind pats grhs
-dsGRHSs ty kind pats (grhs:grhss)
- = dsGRHS ty kind pats grhs `thenDs` \ match_result1 ->
- dsGRHSs ty kind pats grhss `thenDs` \ match_result2 ->
- combineGRHSMatchResults match_result1 match_result2
+dsGRHSs kind pats (grhs:grhss)
+ = dsGRHS kind pats grhs `thenDs` \ match_result1 ->
+ dsGRHSs kind pats grhss `thenDs` \ match_result2 ->
+ returnDs (combineMatchResults match_result1 match_result2)
-dsGRHS ty kind pats (GRHS guard expr locn)
- = putSrcLocDs locn $
- dsExpr expr `thenDs` \ core_expr ->
- let
- expr_fn = \ ignore -> core_expr
- in
- matchGuard guard (DsMatchContext kind pats locn) (MatchResult CantFail ty expr_fn)
+dsGRHS kind pats (GRHS guard locn)
+ = matchGuard guard (DsMatchContext kind pats locn)
\end{code}
-
-
%************************************************************************
%* *
%* matchGuard : make a MatchResult from a guarded RHS *
\begin{code}
matchGuard :: [TypecheckedStmt] -- Guard
-> DsMatchContext -- Context
- -> MatchResult -- What to do if the guard succeeds
-> DsM MatchResult
-matchGuard [] ctx body_result = returnDs body_result
+matchGuard (ExprStmt expr locn : should_be_null) ctx
+ = putSrcLocDs locn (dsExpr expr) `thenDs` \ core_expr ->
+ returnDs (cantFailMatchResult core_expr)
-- Turn an "otherwise" guard is a no-op
-matchGuard (GuardStmt (HsVar v) _ : stmts) ctx body_result
+matchGuard (GuardStmt (HsVar v) _ : stmts) ctx
| uniq == otherwiseIdKey
|| uniq == trueDataConKey
- = matchGuard stmts ctx body_result
+ = matchGuard stmts ctx
where
- uniq = uniqueOf v
-
-matchGuard (GuardStmt expr _ : stmts) ctx body_result
- = matchGuard stmts ctx body_result `thenDs` \ (MatchResult _ ty body_fn) ->
- dsExpr expr `thenDs` \ core_expr ->
- let
- expr_fn = \ fail -> mkCoreIfThenElse core_expr (body_fn fail) fail
- in
- returnDs (MatchResult CanFail ty expr_fn)
-
-matchGuard (LetStmt binds : stmts) ctx body_result
- = matchGuard stmts ctx body_result `thenDs` \ match_result ->
- dsBinds False{-don't auto scc-} binds `thenDs` \ core_binds ->
- returnDs (mkCoLetsMatchResult core_binds match_result)
-
-matchGuard (BindStmt pat rhs _ : stmts) ctx body_result
- = matchGuard stmts ctx body_result `thenDs` \ match_result ->
- dsExpr rhs `thenDs` \ core_rhs ->
- newSysLocalDs (coreExprType core_rhs) `thenDs` \ scrut_var ->
- matchExport [scrut_var] [EqnInfo 1 ctx [pat] match_result] `thenDs` \ match_result' ->
- returnDs (mkCoLetsMatchResult [NonRec scrut_var core_rhs] match_result')
+ uniq = getUnique v
+
+matchGuard (GuardStmt expr locn : stmts) ctx
+ = matchGuard stmts ctx `thenDs` \ match_result ->
+ putSrcLocDs locn (dsExpr 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)
+ -- 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
\end{code}
+
+-- Should *fail* if e returns D
+
+f x | p <- e', let C y# = e, f y# = r1
+ | otherwise = r2
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