%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[DsExpr]{Matching expressions (Exprs)}
\begin{code}
+module DsExpr ( dsExpr, dsLet ) where
+
#include "HsVersions.h"
-module DsExpr ( dsExpr ) where
-import Ubiq
-import DsLoop -- partly to get dsBinds, partly to chk dsExpr
+import HsSyn ( failureFreePat,
+ HsExpr(..), OutPat(..), HsLit(..), ArithSeqInfo(..),
+ Stmt(..), StmtCtxt(..), Match(..), HsBinds(..), MonoBinds(..),
+ mkSimpleMatch
+ )
+import TcHsSyn ( TypecheckedHsExpr, TypecheckedHsBinds,
+ TypecheckedStmt,
+ maybeBoxedPrimType
-import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..),
- Match, Qual, HsBinds, Stmt, PolyType )
-import TcHsSyn ( TypecheckedHsExpr(..), TypecheckedHsBinds(..) )
+ )
import CoreSyn
import DsMonad
+import DsBinds ( dsMonoBinds, AutoScc(..) )
+import DsGRHSs ( dsGuarded )
import DsCCall ( dsCCall )
import DsListComp ( dsListComp )
-import DsUtils ( mkAppDs, mkConDs, mkPrimDs, dsExprToAtom )
-import Match ( matchWrapper )
+import DsUtils ( mkErrorAppDs )
+import Match ( matchWrapper, matchSimply )
-import CoreUnfold ( UnfoldingDetails(..), UnfoldingGuidance(..),
- FormSummary )
-import CoreUtils ( coreExprType, substCoreExpr, argToExpr,
- mkCoreIfThenElse, unTagBinders )
+import CoreUtils ( coreExprType )
import CostCentre ( mkUserCC )
-import Id ( mkTupleCon, idType, nullIdEnv, addOneToIdEnv,
- getIdUnfolding )
-import Literal ( mkMachInt, Literal(..) )
-import MagicUFs ( MagicUnfoldingFun )
-import PprStyle ( PprStyle(..) )
-import PprType ( GenType, GenTyVar )
-import PrelInfo ( mkTupleTy, unitTy, nilDataCon, consDataCon,
- charDataCon, charTy )
-import Pretty ( ppShow )
-import Type ( splitSigmaTy )
-import TyVar ( nullTyVarEnv, addOneToTyVarEnv, GenTyVar )
-import Unique ( Unique )
-import Usage ( UVar(..) )
-import Util ( panic )
-
-primRepFromType = panic "DsExpr.primRepFromType"
-maybeBoxedPrimType = panic "DsExpr.maybeBoxedPrimType"
-splitTyArgs = panic "DsExpr.splitTyArgs"
-
-mk_nil_con ty = mkCon nilDataCon [] [ty] [] -- micro utility...
+import FieldLabel ( FieldLabel )
+import Id ( Id, idType, recordSelectorFieldLabel )
+import Const ( Con(..) )
+import DataCon ( DataCon, dataConId, dataConTyCon, dataConArgTys, dataConFieldLabels )
+import Const ( mkMachInt, Literal(..), mkStrLit )
+import PrelVals ( rEC_CON_ERROR_ID, rEC_UPD_ERROR_ID, iRREFUT_PAT_ERROR_ID )
+import TyCon ( isNewTyCon )
+import DataCon ( isExistentialDataCon )
+import Type ( splitFunTys, mkTyConApp,
+ splitAlgTyConApp, splitTyConApp_maybe,
+ splitAppTy, isUnLiftedType, Type
+ )
+import TysWiredIn ( tupleCon, unboxedTupleCon,
+ consDataCon, listTyCon, mkListTy,
+ charDataCon, charTy, stringTy
+ )
+import BasicTypes ( RecFlag(..) )
+import Maybes ( maybeToBool )
+import Util ( zipEqual, zipWithEqual )
+import Outputable
\end{code}
-The funny business to do with variables is that we look them up in the
-Id-to-Id and Id-to-Id maps that the monadery is carrying
-around; if we get hits, we use the value accordingly.
+
+%************************************************************************
+%* *
+\subsection{dsLet}
+%* *
+%************************************************************************
+
+@dsLet@ is a match-result transformer, taking the MatchResult for the body
+and transforming it into one for the let-bindings enclosing the body.
+
+This may seem a bit odd, but (source) let bindings can contain unboxed
+binds like
+
+ C x# = e
+
+This must be transformed to a case expression and, if the type has
+more than one constructor, may fail.
+
+\begin{code}
+dsLet :: TypecheckedHsBinds -> CoreExpr -> DsM CoreExpr
+
+dsLet EmptyBinds body
+ = returnDs body
+
+dsLet (ThenBinds b1 b2) body
+ = dsLet b2 body `thenDs` \ body' ->
+ dsLet b1 body'
+
+-- Special case for bindings which bind unlifted variables
+dsLet (MonoBind (AbsBinds [] [] binder_triples (PatMonoBind pat grhss loc)) sigs is_rec) body
+ | or [isUnLiftedType (idType g) | (_, g, l) <- binder_triples]
+ = ASSERT (case is_rec of {NonRecursive -> True; other -> False})
+ putSrcLocDs loc $
+ dsGuarded grhss `thenDs` \ rhs ->
+ let
+ body' = foldr bind body binder_triples
+ bind (tyvars, g, l) body = ASSERT( null tyvars )
+ bindNonRec g (Var l) body
+ in
+ mkErrorAppDs iRREFUT_PAT_ERROR_ID result_ty (showSDoc (ppr pat)) `thenDs` \ error_expr ->
+ matchSimply rhs PatBindMatch pat body' error_expr
+ where
+ result_ty = coreExprType body
+
+-- Ordinary case for bindings
+dsLet (MonoBind binds sigs is_rec) body
+ = dsMonoBinds NoSccs binds [] `thenDs` \ prs ->
+ case is_rec of
+ Recursive -> returnDs (Let (Rec prs) body)
+ NonRecursive -> returnDs (foldr mk_let body prs)
+ where
+ mk_let (bndr,rhs) body = Let (NonRec bndr rhs) body
+\end{code}
%************************************************************************
%* *
\begin{code}
dsExpr :: TypecheckedHsExpr -> DsM CoreExpr
-dsExpr (HsVar var) = dsApp (HsVar var) []
+dsExpr e@(HsVar var) = returnDs (Var var)
\end{code}
%************************************************************************
\begin{code}
dsExpr (HsLitOut (HsString s) _)
| _NULL_ s
- = returnDs (mk_nil_con charTy)
+ = returnDs (mkNilExpr charTy)
| _LENGTH_ s == 1
= let
- the_char = mkCon charDataCon [] [] [LitArg (MachChar (_HEAD_ s))]
- the_nil = mk_nil_con charTy
+ the_char = mkConApp charDataCon [mkLit (MachChar (_HEAD_ s))]
+ the_nil = mkNilExpr charTy
+ the_cons = mkConApp consDataCon [Type charTy, the_char, the_nil]
in
- mkConDs consDataCon [charTy] [the_char, the_nil]
+ returnDs the_cons
+
-- "_" => build (\ c n -> c 'c' n) -- LATER
-- "str" ==> build (\ c n -> foldr charTy T c n "str")
{- LATER:
-dsExpr (HsLitOut (HsString str) _) =
- newTyVarsDs [alphaTyVar] `thenDs` \ [new_tyvar] ->
+dsExpr (HsLitOut (HsString str) _)
+ = newTyVarsDs [alphaTyVar] `thenDs` \ [new_tyvar] ->
let
new_ty = mkTyVarTy new_tyvar
in
-- the Core-to-STG pass will wrap it in an application of "unpackCStringId".
dsExpr (HsLitOut (HsString str) _)
- = returnDs (Lit (NoRepStr str))
-
-dsExpr (HsLitOut (HsLitLit s) ty)
- = returnDs ( mkCon data_con [] [] [LitArg (MachLitLit s kind)] )
+ = returnDs (mkLit (NoRepStr str stringTy))
+
+dsExpr (HsLitOut (HsLitLit str) ty)
+ = case (maybeBoxedPrimType ty) of
+ Just (boxing_data_con, prim_ty) ->
+ returnDs ( mkConApp boxing_data_con [mkLit (MachLitLit str prim_ty)] )
+ _ ->
+ pprError "ERROR:"
+ (vcat
+ [ hcat [ text "Cannot see data constructor of ``literal-literal''s type: "
+ , text "value:", quotes (quotes (ptext str))
+ , text "; type: ", ppr ty
+ ]
+ , text "Try compiling with -fno-prune-tydecls."
+ ])
+
where
- (data_con, kind)
+ (data_con, prim_ty)
= case (maybeBoxedPrimType ty) of
+ Just (boxing_data_con, prim_ty) -> (boxing_data_con, prim_ty)
Nothing
- -> error ("ERROR: ``literal-literal'' not a single-constructor type: "++ _UNPK_ s ++"; type: "++(ppShow 80 (ppr PprDebug ty)))
- Just (boxing_data_con, prim_ty)
- -> (boxing_data_con, primRepFromType prim_ty)
+ -> pprPanic "ERROR: ``literal-literal'' not a single-constructor type: "
+ (hcat [ptext str, text "; type: ", ppr ty])
-dsExpr (HsLitOut (HsInt i) _)
- = returnDs (Lit (NoRepInteger i))
+dsExpr (HsLitOut (HsInt i) ty)
+ = returnDs (mkLit (NoRepInteger i ty))
-dsExpr (HsLitOut (HsFrac r) _)
- = returnDs (Lit (NoRepRational r))
+dsExpr (HsLitOut (HsFrac r) ty)
+ = returnDs (mkLit (NoRepRational r ty))
-- others where we know what to do:
dsExpr (HsLitOut (HsIntPrim i) _)
- = if (i >= toInteger minInt && i <= toInteger maxInt) then
- returnDs (Lit (mkMachInt i))
- else
- error ("ERROR: Int constant " ++ show i ++ out_of_range_msg)
+ | (i >= toInteger minInt && i <= toInteger maxInt)
+ = returnDs (mkLit (mkMachInt i))
+ | otherwise
+ = error ("ERROR: Int constant " ++ show i ++ out_of_range_msg)
dsExpr (HsLitOut (HsFloatPrim f) _)
- = returnDs (Lit (MachFloat f))
+ = returnDs (mkLit (MachFloat f))
-- ToDo: range checking needed!
dsExpr (HsLitOut (HsDoublePrim d) _)
- = returnDs (Lit (MachDouble d))
+ = returnDs (mkLit (MachDouble d))
-- ToDo: range checking needed!
dsExpr (HsLitOut (HsChar c) _)
- = returnDs ( mkCon charDataCon [] [] [LitArg (MachChar c)] )
+ = returnDs ( mkConApp charDataCon [mkLit (MachChar c)] )
dsExpr (HsLitOut (HsCharPrim c) _)
- = returnDs (Lit (MachChar c))
+ = returnDs (mkLit (MachChar c))
dsExpr (HsLitOut (HsStringPrim s) _)
- = returnDs (Lit (MachStr s))
+ = returnDs (mkLit (MachStr s))
-- end of literals magic. --
dsExpr expr@(HsLam a_Match)
- = let
- error_msg = "%L" --> "pattern-matching failed in lambda"
- in
- matchWrapper LambdaMatch [a_Match] error_msg `thenDs` \ (binders, matching_code) ->
- returnDs ( mkValLam binders matching_code )
+ = matchWrapper LambdaMatch [a_Match] "lambda" `thenDs` \ (binders, matching_code) ->
+ returnDs (mkLams binders matching_code)
+
+dsExpr expr@(HsApp fun arg)
+ = dsExpr fun `thenDs` \ core_fun ->
+ dsExpr arg `thenDs` \ core_arg ->
+ returnDs (core_fun `App` core_arg)
-dsExpr expr@(HsApp e1 e2) = dsApp expr []
-dsExpr expr@(OpApp e1 op e2) = dsApp expr []
\end{code}
Operator sections. At first it looks as if we can convert
will sort it out.
\begin{code}
+dsExpr (OpApp e1 op _ e2)
+ = dsExpr op `thenDs` \ core_op ->
+ -- for the type of y, we need the type of op's 2nd argument
+ let
+ (x_ty:y_ty:_, _) = splitFunTys (coreExprType core_op)
+ in
+ dsExpr e1 `thenDs` \ x_core ->
+ dsExpr e2 `thenDs` \ y_core ->
+ returnDs (mkApps core_op [x_core, y_core])
+
dsExpr (SectionL expr op)
- = dsExpr op `thenDs` \ core_op ->
- dsExpr expr `thenDs` \ core_expr ->
- dsExprToAtom core_expr $ \ y_atom ->
-
- -- for the type of x, we need the type of op's 2nd argument
+ = dsExpr op `thenDs` \ core_op ->
+ -- for the type of y, we need the type of op's 2nd argument
let
- x_ty = case (splitSigmaTy (coreExprType core_op)) of { (_, _, tau_ty) ->
- case (splitTyArgs tau_ty) of {
- ((_:arg2_ty:_), _) -> arg2_ty;
- _ -> panic "dsExpr:SectionL:arg 2 ty"
- }}
+ (x_ty:y_ty:_, _) = splitFunTys (coreExprType core_op)
in
- newSysLocalDs x_ty `thenDs` \ x_id ->
- returnDs (mkValLam [x_id] (core_op `App` y_atom `App` VarArg x_id))
+ dsExpr expr `thenDs` \ x_core ->
+ newSysLocalDs x_ty `thenDs` \ x_id ->
+ newSysLocalDs y_ty `thenDs` \ y_id ->
+
+ returnDs (bindNonRec x_id x_core $
+ Lam y_id (mkApps core_op [Var x_id, Var y_id]))
-- dsExpr (SectionR op expr) -- \ x -> op x expr
dsExpr (SectionR op expr)
= dsExpr op `thenDs` \ core_op ->
- dsExpr expr `thenDs` \ core_expr ->
- dsExprToAtom core_expr $ \ y_atom ->
-
- -- for the type of x, we need the type of op's 1st argument
+ -- for the type of x, we need the type of op's 2nd argument
let
- x_ty = case (splitSigmaTy (coreExprType core_op)) of { (_, _, tau_ty) ->
- case (splitTyArgs tau_ty) of {
- ((arg1_ty:_), _) -> arg1_ty;
- _ -> panic "dsExpr:SectionR:arg 1 ty"
- }}
+ (x_ty:y_ty:_, _) = splitFunTys (coreExprType core_op)
in
- newSysLocalDs x_ty `thenDs` \ x_id ->
- returnDs (mkValLam [x_id] (core_op `App` VarArg x_id `App` y_atom))
+ dsExpr expr `thenDs` \ y_core ->
+ newSysLocalDs x_ty `thenDs` \ x_id ->
+ newSysLocalDs y_ty `thenDs` \ y_id ->
+
+ returnDs (bindNonRec y_id y_core $
+ Lam x_id (mkApps core_op [Var x_id, Var y_id]))
dsExpr (CCall label args may_gc is_asm result_ty)
= mapDs dsExpr args `thenDs` \ core_args ->
dsExpr (HsSCC cc expr)
= dsExpr expr `thenDs` \ core_expr ->
getModuleAndGroupDs `thenDs` \ (mod_name, group_name) ->
- returnDs ( SCC (mkUserCC cc mod_name group_name) core_expr)
-
-dsExpr expr@(HsCase discrim matches src_loc)
- = putSrcLocDs src_loc $
- dsExpr discrim `thenDs` \ core_discrim ->
- let
- error_msg = "%C" --> "pattern-matching failed in case"
- in
- matchWrapper CaseMatch matches error_msg `thenDs` \ ([discrim_var], matching_code) ->
- returnDs ( mkCoLetAny (NonRec discrim_var core_discrim) matching_code )
+ returnDs (Note (SCC (mkUserCC cc mod_name group_name)) core_expr)
-dsExpr (ListComp expr quals)
- = dsExpr expr `thenDs` \ core_expr ->
- dsListComp core_expr quals
+-- special case to handle unboxed tuple patterns.
-dsExpr (HsLet binds expr)
- = dsBinds binds `thenDs` \ core_binds ->
- dsExpr expr `thenDs` \ core_expr ->
- returnDs ( mkCoLetsAny core_binds core_expr )
+dsExpr (HsCase discrim matches@[Match _ [TuplePat ps boxed] _ _] src_loc)
+ | not boxed && all var_pat ps
+ = putSrcLocDs src_loc $
+ dsExpr discrim `thenDs` \ core_discrim ->
+ matchWrapper CaseMatch matches "case" `thenDs` \ ([discrim_var], matching_code) ->
+ case matching_code of
+ Case (Var x) bndr alts | x == discrim_var ->
+ returnDs (Case core_discrim bndr alts)
+ _ -> panic ("dsExpr: tuple pattern:\n" ++ showSDoc (ppr matching_code))
-dsExpr (HsDoOut stmts m_id mz_id src_loc)
+dsExpr (HsCase discrim matches src_loc)
= putSrcLocDs src_loc $
- panic "dsExpr:HsDoOut"
-
-dsExpr (ExplicitListOut ty xs)
- = case xs of
- [] -> returnDs (mk_nil_con ty)
- (y:ys) ->
- dsExpr y `thenDs` \ core_hd ->
- dsExpr (ExplicitListOut ty ys) `thenDs` \ core_tl ->
- mkConDs consDataCon [ty] [core_hd, core_tl]
-
-dsExpr (ExplicitTuple expr_list)
- = mapDs dsExpr expr_list `thenDs` \ core_exprs ->
- mkConDs (mkTupleCon (length expr_list))
- (map coreExprType core_exprs)
- core_exprs
-
-dsExpr (RecordCon con rbinds) = panic "dsExpr:RecordCon"
-dsExpr (RecordUpd aexp rbinds) = panic "dsExpr:RecordUpd"
+ dsExpr discrim `thenDs` \ core_discrim ->
+ matchWrapper CaseMatch matches "case" `thenDs` \ ([discrim_var], matching_code) ->
+ returnDs (bindNonRec discrim_var core_discrim matching_code)
+
+dsExpr (HsLet binds body)
+ = dsExpr body `thenDs` \ body' ->
+ dsLet binds body'
+
+dsExpr (HsDoOut do_or_lc stmts return_id then_id fail_id result_ty src_loc)
+ | maybeToBool maybe_list_comp
+ = -- Special case for list comprehensions
+ putSrcLocDs src_loc $
+ dsListComp stmts elt_ty
+
+ | otherwise
+ = putSrcLocDs src_loc $
+ dsDo do_or_lc stmts return_id then_id fail_id result_ty
+ where
+ maybe_list_comp
+ = case (do_or_lc, splitTyConApp_maybe result_ty) of
+ (ListComp, Just (tycon, [elt_ty]))
+ | tycon == listTyCon
+ -> Just elt_ty
+ other -> Nothing
+ -- We need the ListComp form to use deListComp (rather than the "do" form)
+ -- because the "return" in a do block is a call to "PrelBase.return", and
+ -- not a ReturnStmt. Only the ListComp form has ReturnStmts
+
+ Just elt_ty = maybe_list_comp
dsExpr (HsIf guard_expr then_expr else_expr src_loc)
= putSrcLocDs src_loc $
dsExpr guard_expr `thenDs` \ core_guard ->
dsExpr then_expr `thenDs` \ core_then ->
dsExpr else_expr `thenDs` \ core_else ->
- returnDs (mkCoreIfThenElse core_guard core_then core_else)
+ returnDs (mkIfThenElse core_guard core_then core_else)
+\end{code}
+
+
+Type lambda and application
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+\begin{code}
+dsExpr (TyLam tyvars expr)
+ = dsExpr expr `thenDs` \ core_expr ->
+ returnDs (mkLams tyvars core_expr)
+
+dsExpr (TyApp expr tys)
+ = dsExpr expr `thenDs` \ core_expr ->
+ returnDs (mkTyApps core_expr tys)
+\end{code}
+
+
+Various data construction things
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+\begin{code}
+dsExpr (ExplicitListOut ty xs)
+ = go xs
+ where
+ list_ty = mkListTy ty
+
+ go [] = returnDs (mkNilExpr ty)
+ go (x:xs) = dsExpr x `thenDs` \ core_x ->
+ go xs `thenDs` \ core_xs ->
+ returnDs (mkConApp consDataCon [Type ty, core_x, core_xs])
+
+dsExpr (ExplicitTuple expr_list boxed)
+ = mapDs dsExpr expr_list `thenDs` \ core_exprs ->
+ returnDs (mkConApp ((if boxed
+ then tupleCon
+ else unboxedTupleCon) (length expr_list))
+ (map (Type . coreExprType) core_exprs ++ core_exprs))
+
+dsExpr (HsCon con_id [ty] [arg])
+ | isNewTyCon tycon
+ = dsExpr arg `thenDs` \ arg' ->
+ returnDs (Note (Coerce result_ty (coreExprType arg')) arg')
+ where
+ result_ty = mkTyConApp tycon [ty]
+ tycon = dataConTyCon con_id
+
+dsExpr (HsCon con_id tys args)
+ = mapDs dsExpr args `thenDs` \ args2 ->
+ returnDs (mkConApp con_id (map Type tys ++ args2))
dsExpr (ArithSeqOut expr (From from))
= dsExpr expr `thenDs` \ expr2 ->
dsExpr from `thenDs` \ from2 ->
- mkAppDs expr2 [] [from2]
+ returnDs (App expr2 from2)
dsExpr (ArithSeqOut expr (FromTo from two))
= dsExpr expr `thenDs` \ expr2 ->
dsExpr from `thenDs` \ from2 ->
dsExpr two `thenDs` \ two2 ->
- mkAppDs expr2 [] [from2, two2]
+ returnDs (mkApps expr2 [from2, two2])
dsExpr (ArithSeqOut expr (FromThen from thn))
= dsExpr expr `thenDs` \ expr2 ->
dsExpr from `thenDs` \ from2 ->
dsExpr thn `thenDs` \ thn2 ->
- mkAppDs expr2 [] [from2, thn2]
+ returnDs (mkApps expr2 [from2, thn2])
dsExpr (ArithSeqOut expr (FromThenTo from thn two))
= dsExpr expr `thenDs` \ expr2 ->
dsExpr from `thenDs` \ from2 ->
dsExpr thn `thenDs` \ thn2 ->
dsExpr two `thenDs` \ two2 ->
- mkAppDs expr2 [] [from2, thn2, two2]
+ returnDs (mkApps expr2 [from2, thn2, two2])
\end{code}
+Record construction and update
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+For record construction we do this (assuming T has three arguments)
+
+ T { op2 = e }
+==>
+ let err = /\a -> recConErr a
+ T (recConErr t1 "M.lhs/230/op1")
+ e
+ (recConErr t1 "M.lhs/230/op3")
+
+recConErr then converts its arugment string into a proper message
+before printing it as
+
+ M.lhs, line 230: missing field op1 was evaluated
+
+
\begin{code}
-dsExpr (TyLam tyvars expr)
- = dsExpr expr `thenDs` \ core_expr ->
- returnDs (mkTyLam tyvars core_expr)
+dsExpr (RecordConOut data_con con_expr rbinds)
+ = dsExpr con_expr `thenDs` \ con_expr' ->
+ let
+ (arg_tys, _) = splitFunTys (coreExprType con_expr')
+
+ mk_arg (arg_ty, lbl)
+ = case [rhs | (sel_id,rhs,_) <- rbinds,
+ lbl == recordSelectorFieldLabel sel_id] of
+ (rhs:rhss) -> ASSERT( null rhss )
+ dsExpr rhs
+ [] -> mkErrorAppDs rEC_CON_ERROR_ID arg_ty (showSDoc (ppr lbl))
+ in
+ mapDs mk_arg (zipEqual "dsExpr:RecordCon" arg_tys (dataConFieldLabels data_con)) `thenDs` \ con_args ->
+ returnDs (mkApps con_expr' con_args)
+\end{code}
+
+Record update is a little harder. Suppose we have the decl:
+
+ data T = T1 {op1, op2, op3 :: Int}
+ | T2 {op4, op2 :: Int}
+ | T3
+
+Then we translate as follows:
-dsExpr expr@(TyApp e tys) = dsApp expr []
+ r { op2 = e }
+===>
+ let op2 = e in
+ case r of
+ T1 op1 _ op3 -> T1 op1 op2 op3
+ T2 op4 _ -> T2 op4 op2
+ other -> recUpdError "M.lhs/230"
+
+It's important that we use the constructor Ids for T1, T2 etc on the
+RHSs, and do not generate a Core Con directly, because the constructor
+might do some argument-evaluation first; and may have to throw away some
+dictionaries.
+
+\begin{code}
+dsExpr (RecordUpdOut record_expr record_out_ty dicts rbinds)
+ = dsExpr record_expr `thenDs` \ record_expr' ->
+
+ -- Desugar the rbinds, and generate let-bindings if
+ -- necessary so that we don't lose sharing
+
+ let
+ ds_rbind (sel_id, rhs, pun_flag)
+ = dsExpr rhs `thenDs` \ rhs' ->
+ returnDs (recordSelectorFieldLabel sel_id, rhs')
+ in
+ mapDs ds_rbind rbinds `thenDs` \ rbinds' ->
+ let
+ record_in_ty = coreExprType record_expr'
+ (tycon, in_inst_tys, cons) = splitAlgTyConApp record_in_ty
+ (_, out_inst_tys, _) = splitAlgTyConApp record_out_ty
+ cons_to_upd = filter has_all_fields cons
+
+ -- initial_args are passed to every constructor
+ initial_args = map Type out_inst_tys ++ map Var dicts
+
+ mk_val_arg field old_arg_id
+ = case [rhs | (f, rhs) <- rbinds', field == f] of
+ (rhs:rest) -> ASSERT(null rest) rhs
+ [] -> Var old_arg_id
+
+ mk_alt con
+ = newSysLocalsDs (dataConArgTys con in_inst_tys) `thenDs` \ arg_ids ->
+ let
+ val_args = zipWithEqual "dsExpr:RecordUpd" mk_val_arg
+ (dataConFieldLabels con) arg_ids
+ rhs = mkApps (mkApps (Var (dataConId con)) initial_args) val_args
+ in
+ returnDs (DataCon con, arg_ids, rhs)
+
+ mk_default
+ | length cons_to_upd == length cons
+ = returnDs []
+ | otherwise
+ = mkErrorAppDs rEC_UPD_ERROR_ID record_out_ty "" `thenDs` \ err ->
+ returnDs [(DEFAULT, [], err)]
+ in
+ -- Record stuff doesn't work for existentials
+ ASSERT( all (not . isExistentialDataCon) cons )
+
+ newSysLocalDs record_in_ty `thenDs` \ case_bndr ->
+ mapDs mk_alt cons_to_upd `thenDs` \ alts ->
+ mk_default `thenDs` \ deflt ->
+
+ returnDs (Case record_expr' case_bndr (alts ++ deflt))
+ where
+ has_all_fields :: DataCon -> Bool
+ has_all_fields con_id
+ = all ok rbinds
+ where
+ con_fields = dataConFieldLabels con_id
+ ok (sel_id, _, _) = recordSelectorFieldLabel sel_id `elem` con_fields
\end{code}
+Dictionary lambda and application
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@DictLam@ and @DictApp@ turn into the regular old things.
(OLD:) @DictFunApp@ also becomes a curried application, albeit slightly more
complicated; reminiscent of fully-applied constructors.
\begin{code}
dsExpr (DictLam dictvars expr)
= dsExpr expr `thenDs` \ core_expr ->
- returnDs( mkValLam dictvars core_expr )
+ returnDs (mkLams dictvars core_expr)
------------------
-dsExpr expr@(DictApp e dicts) -- becomes a curried application
- = dsApp expr []
+dsExpr (DictApp expr dicts) -- becomes a curried application
+ = dsExpr expr `thenDs` \ core_expr ->
+ returnDs (foldl (\f d -> f `App` (Var d)) core_expr dicts)
\end{code}
-@SingleDicts@ become @Locals@; @Dicts@ turn into tuples, unless
-of length 0 or 1.
-@ClassDictLam dictvars methods expr@ is ``the opposite'':
-\begin{verbatim}
-\ x -> case x of ( dictvars-and-methods-tuple ) -> expr
-\end{verbatim}
\begin{code}
-dsExpr (SingleDict dict) -- just a local
- = lookupEnvWithDefaultDs dict (Var dict)
-
-dsExpr (Dictionary dicts methods)
- = -- hey, these things may have been substituted away...
- zipWithDs lookupEnvWithDefaultDs
- dicts_and_methods dicts_and_methods_exprs
- `thenDs` \ core_d_and_ms ->
-
- (case num_of_d_and_ms of
- 0 -> returnDs cocon_unit -- unit
-
- 1 -> returnDs (head core_d_and_ms) -- just a single Id
-
- _ -> -- tuple 'em up
- mkConDs (mkTupleCon num_of_d_and_ms)
- (map coreExprType core_d_and_ms)
- core_d_and_ms
- )
- where
- dicts_and_methods = dicts ++ methods
- dicts_and_methods_exprs = map Var dicts_and_methods
- num_of_d_and_ms = length dicts_and_methods
-
-dsExpr (ClassDictLam dicts methods expr)
- = dsExpr expr `thenDs` \ core_expr ->
- case num_of_d_and_ms of
- 0 -> newSysLocalDs unitTy `thenDs` \ new_x ->
- returnDs (mkValLam [new_x] core_expr)
-
- 1 -> -- no untupling
- returnDs (mkValLam dicts_and_methods core_expr)
-
- _ -> -- untuple it
- newSysLocalDs tuple_ty `thenDs` \ new_x ->
- returnDs (
- Lam (ValBinder new_x)
- (Case (Var new_x)
- (AlgAlts
- [(tuple_con, dicts_and_methods, core_expr)]
- NoDefault)))
- where
- num_of_d_and_ms = length dicts + length methods
- dicts_and_methods = dicts ++ methods
- tuple_ty = mkTupleTy num_of_d_and_ms (map idType dicts_and_methods)
- tuple_con = mkTupleCon num_of_d_and_ms
#ifdef DEBUG
-- HsSyn constructs that just shouldn't be here:
-dsExpr (HsDo _ _) = panic "dsExpr:HsDo"
+dsExpr (HsDo _ _ _) = panic "dsExpr:HsDo"
dsExpr (ExplicitList _) = panic "dsExpr:ExplicitList"
dsExpr (ExprWithTySig _ _) = panic "dsExpr:ExprWithTySig"
dsExpr (ArithSeqIn _) = panic "dsExpr:ArithSeqIn"
#endif
-cocon_unit = mkCon (mkTupleCon 0) [] [] [] -- out here to avoid CAF (sigh)
out_of_range_msg -- ditto
= " out of range: [" ++ show minInt ++ ", " ++ show maxInt ++ "]\n"
\end{code}
%--------------------------------------------------------------------
-@(dsApp e [t_1,..,t_n, e_1,..,e_n])@ returns something with the same
-value as:
-\begin{verbatim}
-e t_1 ... t_n e_1 .. e_n
-\end{verbatim}
-
-We're doing all this so we can saturate constructors (as painlessly as
-possible).
+Basically does the translation given in the Haskell~1.3 report:
\begin{code}
-type DsCoreArg = GenCoreArg CoreExpr{-NB!-} TyVar UVar
-
-dsApp :: TypecheckedHsExpr -- expr to desugar
- -> [DsCoreArg] -- accumulated ty/val args: NB:
- -> DsM CoreExpr -- final result
-
-dsApp (HsApp e1 e2) args
- = dsExpr e2 `thenDs` \ core_e2 ->
- dsApp e1 (VarArg core_e2 : args)
-
-dsApp (OpApp e1 op e2) args
- = dsExpr e1 `thenDs` \ core_e1 ->
- dsExpr e2 `thenDs` \ core_e2 ->
- dsApp op (VarArg core_e1 : VarArg core_e2 : args)
-
-dsApp (DictApp expr dicts) args
- = -- now, those dicts may have been substituted away...
- zipWithDs lookupEnvWithDefaultDs dicts (map Var dicts)
- `thenDs` \ core_dicts ->
- dsApp expr (map VarArg core_dicts ++ args)
-
-dsApp (TyApp expr tys) args
- = dsApp expr (map TyArg tys ++ args)
-
--- we might should look out for SectionLs, etc., here, but we don't
-
-dsApp (HsVar v) args
- = lookupEnvDs v `thenDs` \ maybe_expr ->
- case maybe_expr of
- Just expr -> apply_to_args expr args
-
- Nothing -> -- we're only saturating constructors and PrimOps
- case getIdUnfolding v of
- GenForm _ _ the_unfolding EssentialUnfolding
- -> do_unfold nullTyVarEnv nullIdEnv (unTagBinders the_unfolding) args
-
- _ -> apply_to_args (Var v) args
-
-
-dsApp anything_else args
- = dsExpr anything_else `thenDs` \ core_expr ->
- apply_to_args core_expr args
-
--- a DsM version of mkGenApp:
-apply_to_args :: CoreExpr -> [DsCoreArg] -> DsM CoreExpr
-
-apply_to_args fun args
+dsDo :: StmtCtxt
+ -> [TypecheckedStmt]
+ -> Id -- id for: return m
+ -> Id -- id for: (>>=) m
+ -> Id -- id for: fail m
+ -> Type -- Element type; the whole expression has type (m t)
+ -> DsM CoreExpr
+
+dsDo do_or_lc stmts return_id then_id fail_id result_ty
= let
- (ty_args, val_args) = foldr sep ([],[]) args
+ (_, b_ty) = splitAppTy result_ty -- result_ty must be of the form (m b)
+
+ go [ReturnStmt expr]
+ = dsExpr expr `thenDs` \ expr2 ->
+ returnDs (mkApps (Var return_id) [Type b_ty, expr2])
+
+ go (GuardStmt expr locn : stmts)
+ = do_expr expr locn `thenDs` \ expr2 ->
+ go stmts `thenDs` \ rest ->
+ let msg = "Pattern match failure in do expression, " ++ showSDoc (ppr locn) in
+ returnDs (mkIfThenElse expr2
+ rest
+ (App (App (Var fail_id)
+ (Type b_ty))
+ (mkLit (mkStrLit msg stringTy))))
+
+ go (ExprStmt expr locn : stmts)
+ = do_expr expr locn `thenDs` \ expr2 ->
+ let
+ (_, a_ty) = splitAppTy (coreExprType expr2) -- Must be of form (m a)
+ in
+ if null stmts then
+ returnDs expr2
+ else
+ go stmts `thenDs` \ rest ->
+ newSysLocalDs a_ty `thenDs` \ ignored_result_id ->
+ returnDs (mkApps (Var then_id) [Type a_ty, Type b_ty, expr2,
+ Lam ignored_result_id rest])
+
+ go (LetStmt binds : stmts )
+ = go stmts `thenDs` \ rest ->
+ dsLet binds rest
+
+ go (BindStmt pat expr locn : stmts)
+ = putSrcLocDs locn $
+ dsExpr expr `thenDs` \ expr2 ->
+ let
+ (_, a_ty) = splitAppTy (coreExprType expr2) -- Must be of form (m a)
+ fail_expr = HsApp (TyApp (HsVar fail_id) [b_ty]) (HsLitOut (HsString (_PK_ msg)) stringTy)
+ msg = "Pattern match failure in do expression, " ++ showSDoc (ppr locn)
+ main_match = mkSimpleMatch [pat]
+ (HsDoOut do_or_lc stmts return_id then_id fail_id result_ty locn)
+ (Just result_ty) locn
+ the_matches
+ | failureFreePat pat = [main_match]
+ | otherwise =
+ [ main_match
+ , mkSimpleMatch [WildPat a_ty] fail_expr (Just result_ty) locn
+ ]
+ in
+ matchWrapper DoBindMatch the_matches match_msg
+ `thenDs` \ (binders, matching_code) ->
+ returnDs (mkApps (Var then_id) [Type a_ty, Type b_ty, expr2,
+ mkLams binders matching_code])
in
- mkAppDs fun ty_args val_args
+ go stmts
+
where
- sep a@(LitArg l) (tys,vals) = (tys, (Lit l):vals)
- sep a@(VarArg e) (tys,vals) = (tys, e:vals)
- sep a@(TyArg ty) (tys,vals) = (ty:tys, vals)
- sep a@(UsageArg _) _ = panic "DsExpr:apply_to_args:UsageArg"
+ do_expr expr locn = putSrcLocDs locn (dsExpr expr)
+
+ match_msg = case do_or_lc of
+ DoStmt -> "`do' statement"
+ ListComp -> "comprehension"
\end{code}
\begin{code}
-do_unfold ty_env val_env (Lam (TyBinder tyvar) body) (TyArg ty : args)
- = do_unfold (addOneToTyVarEnv ty_env tyvar ty) val_env body args
-
-do_unfold ty_env val_env (Lam (ValBinder binder) body) (VarArg expr : args)
- = dsExprToAtom expr $ \ arg_atom ->
- do_unfold ty_env
- (addOneToIdEnv val_env binder (argToExpr arg_atom))
- body args
-
-do_unfold ty_env val_env body args
- = -- Clone the remaining part of the template
- uniqSMtoDsM (substCoreExpr val_env ty_env body) `thenDs` \ body' ->
-
- -- Apply result to remaining arguments
- apply_to_args body' args
+var_pat (WildPat _) = True
+var_pat (VarPat _) = True
+var_pat _ = False
\end{code}
+