[project @ 1998-01-08 18:03:08 by simonm]

[ghc-hetmet.git] / ghc / compiler / deSugar / DsGRHSs.lhs

diff --git a/ghc/compiler/deSugar/DsGRHSs.lhs b/ghc/compiler/deSugar/DsGRHSs.lhs
index 5287b22..40b625c 100644 (file)
--- a/ghc/compiler/deSugar/DsGRHSs.lhs
+++ b/ghc/compiler/deSugar/DsGRHSs.lhs
@@ -4,32 +4,32 @@
 \section[DsGRHSs]{Matching guarded right-hand-sides (GRHSs)}
 
 \begin{code}
-#include "HsVersions.h"
-
 module DsGRHSs ( dsGuarded, dsGRHSs ) where
 
-import Ubiq
-import DsLoop          -- break dsExpr/dsBinds-ish loop
+#include "HsVersions.h"
+
+import {-# SOURCE #-} DsExpr  ( dsExpr )
+import {-# SOURCE #-} DsBinds ( dsBinds )
+import {-# SOURCE #-} Match   ( matchExport )
 
 import HsSyn           ( GRHSsAndBinds(..), GRHS(..),
-                         HsExpr, HsBinds )
-import TcHsSyn         ( TypecheckedGRHSsAndBinds(..), TypecheckedGRHS(..),
-                         TypecheckedPat(..), TypecheckedHsBinds(..),
-                         TypecheckedHsExpr(..) )
-import CoreSyn         ( CoreBinding(..), CoreExpr(..) )
+                         HsExpr(..), HsBinds, Stmt(..), 
+                         HsLit, Match, Fixity, DoOrListComp, HsType, ArithSeqInfo
+                        )
+import TcHsSyn         ( TypecheckedGRHSsAndBinds, TypecheckedGRHS,
+                         TypecheckedPat, TypecheckedHsBinds,
+                         TypecheckedHsExpr, TypecheckedStmt
+                       )
+import CoreSyn         ( CoreBinding, GenCoreBinding(..), CoreExpr, mkCoLetsAny )
 
 import DsMonad
 import DsUtils
-
-import CoreUtils       ( escErrorMsg, mkErrorApp )
-import PrelInfo                ( stringTy )
-import PprStyle                ( PprStyle(..) )
-import Pretty          ( ppShow )
+import CoreUtils       ( coreExprType, mkCoreIfThenElse )
+import PrelVals                ( nON_EXHAUSTIVE_GUARDS_ERROR_ID )
 import SrcLoc          ( SrcLoc{-instance-} )
-import Util            ( panic )
-
-mkCoLetsAny = panic "DsGRHSs.mkCoLetsAny"
-mkCoreIfThenElse = panic "DsGRHSs.mkCoreIfThenElse"
+import Type             ( Type )
+import Unique          ( Unique, otherwiseIdKey, trueDataConKey, Uniquable(..) )
+import Outputable
 \end{code}
 
 @dsGuarded@ is used for both @case@ expressions and pattern bindings.
@@ -45,23 +45,15 @@ necessary.  The type argument gives the type of the ei.
 
 \begin{code}
 dsGuarded :: TypecheckedGRHSsAndBinds
-         -> SrcLoc
          -> DsM CoreExpr
 
-dsGuarded (GRHSsAndBindsOut grhss binds err_ty) err_loc
-  = dsBinds binds                              `thenDs` \ core_binds ->
-    dsGRHSs err_ty PatBindMatch [] grhss       `thenDs` \ (MatchResult can_it_fail _ core_grhss_fn _) ->
+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  -> newSysLocalDs stringTy      `thenDs` \ str_var -> -- to hold the String
-                   returnDs (mkCoLetsAny core_binds (core_grhss_fn (error_expr str_var)))
-  where
-    unencoded_part_of_msg = escErrorMsg (ppShow 80 (ppr PprForUser err_loc))
-
-    error_expr :: Id -> CoreExpr
-    error_expr str_var = mkErrorApp err_ty str_var
-                         (unencoded_part_of_msg
-                         ++ "%N") --> ": non-exhaustive guards"
+       CanFail  -> mkErrorAppDs nON_EXHAUSTIVE_GUARDS_ERROR_ID err_ty "" `thenDs` \ error_expr ->
+                   returnDs (mkCoLetsAny core_binds (core_grhss_fn error_expr))
 \end{code}
 
 Desugar a list of (grhs, expr) pairs [grhs = guarded
@@ -88,24 +80,57 @@ dsGRHSs ty kind pats (grhs:grhss)
     dsGRHSs ty kind pats grhss `thenDs` \ match_result2 ->
     combineGRHSMatchResults match_result1 match_result2
 
-dsGRHS ty kind pats (OtherwiseGRHS expr locn)
-  = putSrcLocDs locn            (
+dsGRHS ty kind pats (GRHS guard expr locn)
+  = putSrcLocDs locn $
     dsExpr expr        `thenDs` \ core_expr ->
     let
        expr_fn = \ ignore -> core_expr
     in
-    returnDs (MatchResult CantFail ty expr_fn (DsMatchContext kind pats locn))
-    )
+    matchGuard guard (DsMatchContext kind pats locn) (MatchResult CantFail ty expr_fn) 
+\end{code}
 
-dsGRHS ty kind pats (GRHS guard expr locn)
-  = putSrcLocDs locn            (
-    dsExpr guard       `thenDs` \ core_guard ->
-    dsExpr expr        `thenDs` \ core_expr  ->
+
+
+
+%************************************************************************
+%*                                                                     *
+%*  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
+
+       -- Turn an "otherwise" guard is a no-op
+matchGuard (GuardStmt (HsVar v) _ : stmts) ctx body_result
+  |  uniq == otherwiseIdKey
+  || uniq == trueDataConKey
+  = matchGuard stmts ctx body_result
+  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_guard core_expr fail
+       expr_fn = \ fail -> mkCoreIfThenElse core_expr (body_fn fail) fail
     in
-    returnDs (MatchResult CanFail ty expr_fn (DsMatchContext kind pats locn))
-    )
+    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')
 \end{code}
-
-