%
-% (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, dsLExpr, dsLocalBinds, dsValBinds, dsLit ) where
+
#include "HsVersions.h"
-module DsExpr ( dsExpr ) where
+import Match ( matchWrapper, matchSinglePat, matchEquations )
+import MatchLit ( dsLit, dsOverLit )
+import DsBinds ( dsLHsBinds, dsCoercion )
+import DsGRHSs ( dsGuarded )
+import DsListComp ( dsListComp, dsPArrComp )
+import DsUtils ( mkErrorAppDs, mkStringExpr, mkConsExpr, mkNilExpr,
+ extractMatchResult, cantFailMatchResult, matchCanFail,
+ mkCoreTupTy, selectSimpleMatchVarL, lookupEvidence, selectMatchVar )
+import DsArrows ( dsProcExpr )
+import DsMonad
+
+#ifdef GHCI
+ -- Template Haskell stuff iff bootstrapped
+import DsMeta ( dsBracket )
+#endif
-import Ubiq
-import DsLoop -- partly to get dsBinds, partly to chk dsExpr
+import HsSyn
+import TcHsSyn ( hsPatType, mkVanillaTuplePat )
-import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..),
- Match, Qual, HsBinds, Stmt, PolyType )
-import TcHsSyn ( TypecheckedHsExpr(..), TypecheckedHsBinds(..),
- TypecheckedRecordBinds(..)
- )
+-- NB: The desugarer, which straddles the source and Core worlds, sometimes
+-- needs to see source types (newtypes etc), and sometimes not
+-- So WATCH OUT; check each use of split*Ty functions.
+-- Sigh. This is a pain.
+
+import TcType ( tcSplitAppTy, tcSplitFunTys, tcTyConAppTyCon,
+ tcTyConAppArgs, isUnLiftedType, Type, mkAppTy )
+import Type ( funArgTy, splitFunTys, isUnboxedTupleType, mkFunTy )
import CoreSyn
+import CoreUtils ( exprType, mkIfThenElse, bindNonRec )
-import DsMonad
-import DsCCall ( dsCCall )
-import DsListComp ( dsListComp )
-import DsUtils ( mkAppDs, mkConDs, mkPrimDs, dsExprToAtom,
- mkErrorAppDs, showForErr
- )
-import Match ( matchWrapper )
-
-import CoreUnfold ( UnfoldingDetails(..), UnfoldingGuidance(..),
- FormSummary )
-import CoreUtils ( coreExprType, substCoreExpr, argToExpr,
- mkCoreIfThenElse, unTagBinders )
import CostCentre ( mkUserCC )
-import FieldLabel ( FieldLabel{-instance Eq/Outputable-} )
-import Id ( mkTupleCon, idType, nullIdEnv, addOneToIdEnv,
- getIdUnfolding, dataConArgTys, dataConFieldLabels,
- recordSelectorFieldLabel
- )
-import Literal ( mkMachInt, Literal(..) )
-import MagicUFs ( MagicUnfoldingFun )
-import PprStyle ( PprStyle(..) )
-import PprType ( GenType )
-import PrelInfo ( mkTupleTy, unitTy, nilDataCon, consDataCon,
- charDataCon, charTy, rEC_CON_ERROR_ID,
- rEC_UPD_ERROR_ID
- )
-import Pretty ( ppShow, ppBesides, ppPStr, ppStr )
-import Type ( splitSigmaTy, splitFunTy, typePrimRep,
- getAppDataTyCon
- )
-import TyVar ( nullTyVarEnv, addOneToTyVarEnv )
-import Usage ( UVar(..) )
-import Util ( zipEqual, pprError, panic, assertPanic )
-
-maybeBoxedPrimType = panic "DsExpr.maybeBoxedPrimType"
-splitTyArgs = panic "DsExpr.splitTyArgs"
-
-mk_nil_con ty = mkCon nilDataCon [] [ty] [] -- micro utility...
+import Id ( Id, idType, idName, idDataCon )
+import PrelInfo ( rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID )
+import DataCon ( DataCon, dataConWrapId, dataConFieldLabels, dataConInstOrigArgTys )
+import DataCon ( isVanillaDataCon )
+import TyCon ( FieldLabel, tyConDataCons )
+import TysWiredIn ( tupleCon )
+import BasicTypes ( RecFlag(..), Boxity(..), ipNameName )
+import PrelNames ( toPName,
+ returnMName, bindMName, thenMName, failMName,
+ mfixName )
+import SrcLoc ( Located(..), unLoc, getLoc, noLoc )
+import Util ( zipEqual, zipWithEqual )
+import Bag ( bagToList )
+import Outputable
+import FastString
\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[DsExpr-vars-and-cons]{Variables and constructors}
+ dsLocalBinds, dsValBinds
%* *
%************************************************************************
\begin{code}
-dsExpr :: TypecheckedHsExpr -> DsM CoreExpr
-
-dsExpr (HsVar var) = dsApp (HsVar var) []
-\end{code}
+dsLocalBinds :: HsLocalBinds Id -> CoreExpr -> DsM CoreExpr
+dsLocalBinds EmptyLocalBinds body = return body
+dsLocalBinds (HsValBinds binds) body = dsValBinds binds body
+dsLocalBinds (HsIPBinds binds) body = dsIPBinds binds body
+
+-------------------------
+dsValBinds :: HsValBinds Id -> CoreExpr -> DsM CoreExpr
+dsValBinds (ValBindsOut binds _) body = foldrDs ds_val_bind body binds
+
+-------------------------
+dsIPBinds (IPBinds ip_binds dict_binds) body
+ = do { prs <- dsLHsBinds dict_binds
+ ; let inner = foldr (\(x,r) e -> Let (NonRec x r) e) body prs
+ ; foldrDs ds_ip_bind inner ip_binds }
+ where
+ ds_ip_bind (L _ (IPBind n e)) body
+ = dsLExpr e `thenDs` \ e' ->
+ returnDs (Let (NonRec (ipNameName n) e') body)
+
+-------------------------
+ds_val_bind :: (RecFlag, LHsBinds Id) -> CoreExpr -> DsM CoreExpr
+-- Special case for bindings which bind unlifted variables
+-- We need to do a case right away, rather than building
+-- a tuple and doing selections.
+-- Silently ignore INLINE and SPECIALISE pragmas...
+ds_val_bind (NonRecursive, hsbinds) body
+ | [L _ (AbsBinds [] [] exports binds)] <- bagToList hsbinds,
+ (L loc bind : null_binds) <- bagToList binds,
+ isBangHsBind bind
+ || isUnboxedTupleBind bind
+ || or [isUnLiftedType (idType g) | (_, g, _, _) <- exports]
+ = let
+ body_w_exports = foldr bind_export body exports
+ bind_export (tvs, g, l, _) body = ASSERT( null tvs )
+ bindNonRec g (Var l) body
+ in
+ ASSERT (null null_binds)
+ -- Non-recursive, non-overloaded bindings only come in ones
+ -- ToDo: in some bizarre case it's conceivable that there
+ -- could be dict binds in the 'binds'. (See the notes
+ -- below. Then pattern-match would fail. Urk.)
+ putSrcSpanDs loc $
+ case bind of
+ FunBind { fun_id = L _ fun, fun_matches = matches, fun_co_fn = co_fn }
+ -> matchWrapper (FunRhs (idName fun)) matches `thenDs` \ (args, rhs) ->
+ ASSERT( null args ) -- Functions aren't lifted
+ ASSERT( isIdCoercion co_fn )
+ returnDs (bindNonRec fun rhs body_w_exports)
+
+ PatBind {pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty }
+ -> -- let C x# y# = rhs in body
+ -- ==> case rhs of C x# y# -> body
+ putSrcSpanDs loc $
+ do { rhs <- dsGuarded grhss ty
+ ; let upat = unLoc pat
+ eqn = EqnInfo { eqn_wrap = idWrapper, eqn_pats = [upat],
+ eqn_rhs = cantFailMatchResult body_w_exports }
+ ; var <- selectMatchVar upat ty
+ ; result <- matchEquations PatBindRhs [var] [eqn] (exprType body)
+ ; return (scrungleMatch var rhs result) }
+
+ other -> pprPanic "dsLet: unlifted" (pprLHsBinds hsbinds $$ ppr body)
+
+
+-- Ordinary case for bindings; none should be unlifted
+ds_val_bind (is_rec, binds) body
+ = do { prs <- dsLHsBinds binds
+ ; ASSERT( not (any (isUnLiftedType . idType . fst) prs) )
+ case prs of
+ [] -> return body
+ other -> return (Let (Rec prs) body) }
+ -- Use a Rec regardless of is_rec.
+ -- Why? Because it allows the binds to be all
+ -- mixed up, which is what happens in one rare case
+ -- Namely, for an AbsBind with no tyvars and no dicts,
+ -- but which does have dictionary bindings.
+ -- See notes with TcSimplify.inferLoop [NO TYVARS]
+ -- It turned out that wrapping a Rec here was the easiest solution
+ --
+ -- NB The previous case dealt with unlifted bindings, so we
+ -- only have to deal with lifted ones now; so Rec is ok
+
+isUnboxedTupleBind :: HsBind Id -> Bool
+isUnboxedTupleBind (PatBind { pat_rhs_ty = ty }) = isUnboxedTupleType ty
+isUnboxedTupleBind other = False
+
+scrungleMatch :: Id -> CoreExpr -> CoreExpr -> CoreExpr
+-- Returns something like (let var = scrut in body)
+-- but if var is an unboxed-tuple type, it inlines it in a fragile way
+-- Special case to handle unboxed tuple patterns; they can't appear nested
+-- The idea is that
+-- case e of (# p1, p2 #) -> rhs
+-- should desugar to
+-- case e of (# x1, x2 #) -> ... match p1, p2 ...
+-- NOT
+-- let x = e in case x of ....
+--
+-- But there may be a big
+-- let fail = ... in case e of ...
+-- wrapping the whole case, which complicates matters slightly
+-- It all seems a bit fragile. Test is dsrun013.
+
+scrungleMatch var scrut body
+ | isUnboxedTupleType (idType var) = scrungle body
+ | otherwise = bindNonRec var scrut body
+ where
+ scrungle (Case (Var x) bndr ty alts)
+ | x == var = Case scrut bndr ty alts
+ scrungle (Let binds body) = Let binds (scrungle body)
+ scrungle other = panic ("scrungleMatch: tuple pattern:\n" ++ showSDoc (ppr other))
+\end{code}
%************************************************************************
%* *
-\subsection[DsExpr-literals]{Literals}
+\subsection[DsExpr-vars-and-cons]{Variables, constructors, literals}
%* *
%************************************************************************
-We give int/float literals type Integer and Rational, respectively.
-The typechecker will (presumably) have put \tr{from{Integer,Rational}s}
-around them.
-
-ToDo: put in range checks for when converting "i"
-(or should that be in the typechecker?)
-
-For numeric literals, we try to detect there use at a standard type
-(Int, Float, etc.) are directly put in the right constructor.
-[NB: down with the @App@ conversion.]
-Otherwise, we punt, putting in a "NoRep" Core literal (where the
-representation decisions are delayed)...
-
-See also below where we look for @DictApps@ for \tr{plusInt}, etc.
-
\begin{code}
-dsExpr (HsLitOut (HsString s) _)
- | _NULL_ s
- = returnDs (mk_nil_con charTy)
-
- | _LENGTH_ s == 1
- = let
- the_char = mkCon charDataCon [] [] [LitArg (MachChar (_HEAD_ s))]
- the_nil = mk_nil_con charTy
- in
- mkConDs consDataCon [charTy] [the_char, the_nil]
-
--- "_" => 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] ->
- let
- new_ty = mkTyVarTy new_tyvar
- in
- newSysLocalsDs [
- charTy `mkFunTy` (new_ty `mkFunTy` new_ty),
- new_ty,
- mkForallTy [alphaTyVar]
- ((charTy `mkFunTy` (alphaTy `mkFunTy` alphaTy))
- `mkFunTy` (alphaTy `mkFunTy` alphaTy))
- ] `thenDs` \ [c,n,g] ->
- returnDs (mkBuild charTy new_tyvar c n g (
- foldl App
- (CoTyApp (CoTyApp (Var foldrId) charTy) new_ty) *** ensure non-prim type ***
- [VarArg c,VarArg n,LitArg (NoRepStr str)]))
--}
-
--- otherwise, leave it as a NoRepStr;
--- 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)] )
- where
- (data_con, kind)
- = case (maybeBoxedPrimType ty) of
- Just (boxing_data_con, prim_ty)
- -> (boxing_data_con, typePrimRep prim_ty)
- Nothing
- -> pprError "ERROR: ``literal-literal'' not a single-constructor type: "
- (ppBesides [ppPStr s, ppStr "; type: ", ppr PprDebug ty])
-
-dsExpr (HsLitOut (HsInt i) _)
- = returnDs (Lit (NoRepInteger i))
-
-dsExpr (HsLitOut (HsFrac r) _)
- = returnDs (Lit (NoRepRational r))
+dsLExpr :: LHsExpr Id -> DsM CoreExpr
+dsLExpr (L loc e) = putSrcSpanDs loc $ dsExpr e
--- others where we know what to do:
+dsExpr :: HsExpr Id -> DsM CoreExpr
-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)
+dsExpr (HsPar e) = dsLExpr e
+dsExpr (ExprWithTySigOut e _) = dsLExpr e
+dsExpr (HsVar var) = returnDs (Var var)
+dsExpr (HsIPVar ip) = returnDs (Var (ipNameName ip))
+dsExpr (HsLit lit) = dsLit lit
+dsExpr (HsOverLit lit) = dsOverLit lit
-dsExpr (HsLitOut (HsFloatPrim f) _)
- = returnDs (Lit (MachFloat f))
- -- ToDo: range checking needed!
-
-dsExpr (HsLitOut (HsDoublePrim d) _)
- = returnDs (Lit (MachDouble d))
- -- ToDo: range checking needed!
-
-dsExpr (HsLitOut (HsChar c) _)
- = returnDs ( mkCon charDataCon [] [] [LitArg (MachChar c)] )
-
-dsExpr (HsLitOut (HsCharPrim c) _)
- = returnDs (Lit (MachChar c))
-
-dsExpr (HsLitOut (HsStringPrim s) _)
- = returnDs (Lit (MachStr s))
-
--- end of literals magic. --
+dsExpr (NegApp expr neg_expr)
+ = do { core_expr <- dsLExpr expr
+ ; core_neg <- dsExpr neg_expr
+ ; return (core_neg `App` core_expr) }
dsExpr expr@(HsLam a_Match)
- = matchWrapper LambdaMatch [a_Match] "lambda" `thenDs` \ (binders, matching_code) ->
- returnDs ( mkValLam binders matching_code )
+ = matchWrapper LambdaExpr a_Match `thenDs` \ (binders, matching_code) ->
+ returnDs (mkLams binders matching_code)
-dsExpr expr@(HsApp e1 e2) = dsApp expr []
-dsExpr expr@(OpApp e1 op e2) = dsApp expr []
+dsExpr expr@(HsApp fun arg)
+ = dsLExpr fun `thenDs` \ core_fun ->
+ dsLExpr arg `thenDs` \ core_arg ->
+ returnDs (core_fun `App` core_arg)
\end{code}
Operator sections. At first it looks as if we can convert
will sort it out.
\begin{code}
+dsExpr (OpApp e1 op _ e2)
+ = dsLExpr op `thenDs` \ core_op ->
+ -- for the type of y, we need the type of op's 2nd argument
+ dsLExpr e1 `thenDs` \ x_core ->
+ dsLExpr 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
+ = dsLExpr 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 (exprType core_op)
+ -- Must look through an implicit-parameter type;
+ -- newtype impossible; hence Type.splitFunTys
in
- newSysLocalDs x_ty `thenDs` \ x_id ->
- returnDs (mkValLam [x_id] (core_op `App` y_atom `App` VarArg x_id))
+ dsLExpr expr `thenDs` \ x_core ->
+ newSysLocalDs x_ty `thenDs` \ x_id ->
+ newSysLocalDs y_ty `thenDs` \ 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 ->
+ returnDs (bindNonRec x_id x_core $
+ Lam y_id (mkApps core_op [Var x_id, Var y_id]))
- -- for the type of x, we need the type of op's 1st argument
+-- dsLExpr (SectionR op expr) -- \ x -> op x expr
+dsExpr (SectionR op expr)
+ = dsLExpr op `thenDs` \ core_op ->
+ -- 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 (exprType core_op)
+ -- See comment with SectionL
in
- newSysLocalDs x_ty `thenDs` \ x_id ->
- returnDs (mkValLam [x_id] (core_op `App` VarArg x_id `App` y_atom))
+ dsLExpr expr `thenDs` \ y_core ->
+ newSysLocalDs x_ty `thenDs` \ x_id ->
+ newSysLocalDs y_ty `thenDs` \ y_id ->
-dsExpr (CCall label args may_gc is_asm result_ty)
- = mapDs dsExpr args `thenDs` \ core_args ->
- dsCCall label core_args may_gc is_asm result_ty
- -- dsCCall does all the unboxification, etc.
+ returnDs (bindNonRec y_id y_core $
+ Lam x_id (mkApps core_op [Var x_id, Var y_id]))
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 ->
- matchWrapper CaseMatch matches "case" `thenDs` \ ([discrim_var], matching_code) ->
- returnDs ( mkCoLetAny (NonRec discrim_var core_discrim) matching_code )
-
-dsExpr (ListComp expr quals)
- = dsExpr expr `thenDs` \ core_expr ->
- dsListComp core_expr quals
-
-dsExpr (HsLet binds expr)
- = dsBinds binds `thenDs` \ core_binds ->
- dsExpr expr `thenDs` \ core_expr ->
- returnDs ( mkCoLetsAny core_binds core_expr )
-
-dsExpr (HsDoOut stmts m_id mz_id src_loc)
- = putSrcLocDs src_loc $
- panic "dsExpr:HsDoOut"
-
-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)
+ = dsLExpr expr `thenDs` \ core_expr ->
+ getModuleDs `thenDs` \ mod_name ->
+ returnDs (Note (SCC (mkUserCC cc mod_name)) core_expr)
+
+
+-- hdaume: core annotation
+
+dsExpr (HsCoreAnn fs expr)
+ = dsLExpr expr `thenDs` \ core_expr ->
+ returnDs (Note (CoreNote $ unpackFS fs) core_expr)
+
+dsExpr (HsCase discrim matches)
+ = dsLExpr discrim `thenDs` \ core_discrim ->
+ matchWrapper CaseAlt matches `thenDs` \ ([discrim_var], matching_code) ->
+ returnDs (scrungleMatch discrim_var core_discrim matching_code)
+dsExpr (HsLet binds body)
+ = dsLExpr body `thenDs` \ body' ->
+ dsLocalBinds binds body'
+
+-- We need the `ListComp' form to use `deListComp' (rather than the "do" form)
+-- because the interpretation of `stmts' depends on what sort of thing it is.
+--
+dsExpr (HsDo ListComp stmts body result_ty)
+ = -- Special case for list comprehensions
+ dsListComp stmts body elt_ty
+ where
+ [elt_ty] = tcTyConAppArgs result_ty
+
+dsExpr (HsDo DoExpr stmts body result_ty)
+ = dsDo stmts body result_ty
+
+dsExpr (HsDo (MDoExpr tbl) stmts body result_ty)
+ = dsMDo tbl stmts body result_ty
+
+dsExpr (HsDo PArrComp stmts body result_ty)
+ = -- Special case for array comprehensions
+ dsPArrComp (map unLoc stmts) body elt_ty
+ where
+ [elt_ty] = tcTyConAppArgs result_ty
+
+dsExpr (HsIf guard_expr then_expr else_expr)
+ = dsLExpr guard_expr `thenDs` \ core_guard ->
+ dsLExpr then_expr `thenDs` \ core_then ->
+ dsLExpr else_expr `thenDs` \ core_else ->
+ returnDs (mkIfThenElse core_guard core_then core_else)
\end{code}
-Type lambda and application
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
+\noindent
+\underline{\bf Type lambda and application}
+% ~~~~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
dsExpr (TyLam tyvars expr)
- = dsExpr expr `thenDs` \ core_expr ->
- returnDs (mkTyLam tyvars core_expr)
+ = dsLExpr expr `thenDs` \ core_expr ->
+ returnDs (mkLams tyvars core_expr)
-dsExpr expr@(TyApp e tys) = dsApp expr []
+dsExpr (TyApp expr tys)
+ = dsLExpr expr `thenDs` \ core_expr ->
+ returnDs (mkTyApps core_expr tys)
\end{code}
-Various data construction things
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+\noindent
+\underline{\bf Various data construction things}
+% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
-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 (HsCon con tys args)
- = mapDs dsExpr args `thenDs` \ args_exprs ->
- mkConDs con tys args_exprs
-
-dsExpr (ArithSeqOut expr (From from))
+dsExpr (ExplicitList ty xs)
+ = go xs
+ where
+ go [] = returnDs (mkNilExpr ty)
+ go (x:xs) = dsLExpr x `thenDs` \ core_x ->
+ go xs `thenDs` \ core_xs ->
+ returnDs (mkConsExpr ty core_x core_xs)
+
+-- we create a list from the array elements and convert them into a list using
+-- `PrelPArr.toP'
+--
+-- * the main disadvantage to this scheme is that `toP' traverses the list
+-- twice: once to determine the length and a second time to put to elements
+-- into the array; this inefficiency could be avoided by exposing some of
+-- the innards of `PrelPArr' to the compiler (ie, have a `PrelPArrBase') so
+-- that we can exploit the fact that we already know the length of the array
+-- here at compile time
+--
+dsExpr (ExplicitPArr ty xs)
+ = dsLookupGlobalId toPName `thenDs` \toP ->
+ dsExpr (ExplicitList ty xs) `thenDs` \coreList ->
+ returnDs (mkApps (Var toP) [Type ty, coreList])
+
+dsExpr (ExplicitTuple expr_list boxity)
+ = mappM dsLExpr expr_list `thenDs` \ core_exprs ->
+ returnDs (mkConApp (tupleCon boxity (length expr_list))
+ (map (Type . exprType) core_exprs ++ core_exprs))
+
+dsExpr (ArithSeq expr (From from))
+ = dsExpr expr `thenDs` \ expr2 ->
+ dsLExpr from `thenDs` \ from2 ->
+ returnDs (App expr2 from2)
+
+dsExpr (ArithSeq expr (FromTo from two))
= dsExpr expr `thenDs` \ expr2 ->
- dsExpr from `thenDs` \ from2 ->
- mkAppDs expr2 [] [from2]
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr two `thenDs` \ two2 ->
+ returnDs (mkApps expr2 [from2, two2])
-dsExpr (ArithSeqOut expr (FromTo from two))
+dsExpr (ArithSeq expr (FromThen from thn))
= dsExpr expr `thenDs` \ expr2 ->
- dsExpr from `thenDs` \ from2 ->
- dsExpr two `thenDs` \ two2 ->
- mkAppDs expr2 [] [from2, two2]
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr thn `thenDs` \ thn2 ->
+ returnDs (mkApps expr2 [from2, thn2])
-dsExpr (ArithSeqOut expr (FromThen from thn))
+dsExpr (ArithSeq expr (FromThenTo from thn two))
= dsExpr expr `thenDs` \ expr2 ->
- dsExpr from `thenDs` \ from2 ->
- dsExpr thn `thenDs` \ thn2 ->
- mkAppDs expr2 [] [from2, thn2]
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr thn `thenDs` \ thn2 ->
+ dsLExpr two `thenDs` \ two2 ->
+ returnDs (mkApps expr2 [from2, thn2, two2])
-dsExpr (ArithSeqOut expr (FromThenTo from thn two))
+dsExpr (PArrSeq expr (FromTo from two))
= dsExpr expr `thenDs` \ expr2 ->
- dsExpr from `thenDs` \ from2 ->
- dsExpr thn `thenDs` \ thn2 ->
- dsExpr two `thenDs` \ two2 ->
- mkAppDs expr2 [] [from2, thn2, two2]
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr two `thenDs` \ two2 ->
+ returnDs (mkApps expr2 [from2, two2])
+
+dsExpr (PArrSeq expr (FromThenTo from thn two))
+ = dsExpr expr `thenDs` \ expr2 ->
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr thn `thenDs` \ thn2 ->
+ dsLExpr two `thenDs` \ two2 ->
+ returnDs (mkApps expr2 [from2, thn2, two2])
+
+dsExpr (PArrSeq expr _)
+ = panic "DsExpr.dsExpr: Infinite parallel array!"
+ -- the parser shouldn't have generated it and the renamer and typechecker
+ -- shouldn't have let it through
\end{code}
-Record construction and update
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+\noindent
+\underline{\bf Record construction and update}
+% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For record construction we do this (assuming T has three arguments)
-
+\begin{verbatim}
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
+\end{verbatim}
+@recConErr@ then converts its arugment string into a proper message
before printing it as
-
+\begin{verbatim}
M.lhs, line 230: missing field op1 was evaluated
+\end{verbatim}
+We also handle @C{}@ as valid construction syntax for an unlabelled
+constructor @C@, setting all of @C@'s fields to bottom.
\begin{code}
-dsExpr (RecordCon con_expr rbinds)
+dsExpr (RecordCon (L _ data_con_id) con_expr rbinds)
= dsExpr con_expr `thenDs` \ con_expr' ->
let
- con_id = get_con_id con_expr'
- (arg_tys, data_ty) = splitFunTy (idType con_id)
-
- 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 (showForErr lbl)
+ (arg_tys, _) = tcSplitFunTys (exprType con_expr')
+ -- A newtype in the corner should be opaque;
+ -- hence TcType.tcSplitFunTys
+
+ mk_arg (arg_ty, lbl) -- Selector id has the field label as its name
+ = case [rhs | (L _ sel_id, rhs) <- rbinds, lbl == idName sel_id] of
+ (rhs:rhss) -> ASSERT( null rhss )
+ dsLExpr rhs
+ [] -> mkErrorAppDs rEC_CON_ERROR_ID arg_ty (showSDoc (ppr lbl))
+ unlabelled_bottom arg_ty = mkErrorAppDs rEC_CON_ERROR_ID arg_ty ""
+
+ labels = dataConFieldLabels (idDataCon data_con_id)
+ -- The data_con_id is guaranteed to be the wrapper id of the constructor
in
- mapDs mk_arg (arg_tys `zip` dataConFieldLabels con_id) `thenDs` \ con_args ->
- mkAppDs con_expr' [] con_args
- where
- -- The "con_expr'" is simply an application of the constructor Id
- -- to types and (perhaps) dictionaries. This boring little
- -- function gets the constructor out.
- get_con_id (App fun _) = get_con_id fun
- get_con_id (Var con) = con
+ (if null labels
+ then mappM unlabelled_bottom arg_tys
+ else mappM mk_arg (zipEqual "dsExpr:RecordCon" arg_tys labels))
+ `thenDs` \ con_args ->
+
+ returnDs (mkApps con_expr' con_args)
\end{code}
Record update is a little harder. Suppose we have the decl:
-
+\begin{verbatim}
data T = T1 {op1, op2, op3 :: Int}
- | T2 {op4, op1 :: Int}
+ | T2 {op4, op2 :: Int}
| T3
-
+\end{verbatim}
Then we translate as follows:
-
+\begin{verbatim}
r { op2 = e }
===>
let op2 = e in
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
+\end{verbatim}
+It's important that we use the constructor Ids for @T1@, @T2@ etc on the
+RHSs, and do not generate a Core constructor application directly, because the constructor
might do some argument-evaluation first; and may have to throw away some
dictionaries.
\begin{code}
-dsExpr (RecordUpdOut record_expr dicts rbinds)
- = dsExpr record_expr `thenDs` \ record_expr' ->
+dsExpr (RecordUpd record_expr [] record_in_ty record_out_ty)
+ = dsLExpr record_expr
+
+dsExpr expr@(RecordUpd record_expr rbinds record_in_ty record_out_ty)
+ = dsLExpr record_expr `thenDs` \ record_expr' ->
-- Desugar the rbinds, and generate let-bindings if
-- necessary so that we don't lose sharing
--- dsRbinds rbinds $ \ rbinds' ->
- let rbinds' = panic "dsExpr:RecordUpdOut:rbinds'" in
+
let
- record_ty = coreExprType record_expr'
- (tycon, inst_tys, cons) = getAppDataTyCon record_ty
- cons_to_upd = filter has_all_fields cons
-
- -- initial_args are passed to every constructor
- initial_args = map TyArg inst_tys ++ map VarArg dicts
-
- mk_val_arg (field, arg_id)
- = case [arg | (f, arg) <- rbinds', f==field] of
- (arg:args) -> ASSERT(null args)
- arg
- [] -> VarArg arg_id
+ in_inst_tys = tcTyConAppArgs record_in_ty -- Newtype opaque
+ out_inst_tys = tcTyConAppArgs record_out_ty -- Newtype opaque
+ in_out_ty = mkFunTy record_in_ty record_out_ty
+
+ mk_val_arg field old_arg_id
+ = case [rhs | (L _ sel_id, rhs) <- rbinds, field == idName sel_id] of
+ (rhs:rest) -> ASSERT(null rest) rhs
+ [] -> nlHsVar old_arg_id
mk_alt con
- = newSysLocalsDs (dataConArgTys con inst_tys) `thenDs` \ arg_ids ->
+ = newSysLocalsDs (dataConInstOrigArgTys con in_inst_tys) `thenDs` \ arg_ids ->
+ -- This call to dataConInstOrigArgTys won't work for existentials
+ -- but existentials don't have record types anyway
let
- val_args = map mk_val_arg (dataConFieldLabels con `zipEqual` arg_ids)
+ val_args = zipWithEqual "dsExpr:RecordUpd" mk_val_arg
+ (dataConFieldLabels con) arg_ids
+ rhs = foldl (\a b -> nlHsApp a b)
+ (noLoc $ TyApp (nlHsVar (dataConWrapId con))
+ out_inst_tys)
+ val_args
in
- returnDs (con, arg_ids, mkGenApp (mkGenApp (Var con) initial_args) val_args)
-
- mk_default
- | length cons_to_upd == length cons
- = returnDs NoDefault
- | otherwise
- = newSysLocalDs record_ty `thenDs` \ deflt_id ->
- mkErrorAppDs rEC_UPD_ERROR_ID record_ty "" `thenDs` \ err ->
- returnDs (BindDefault deflt_id err)
+ returnDs (mkSimpleMatch [noLoc $ ConPatOut (noLoc con) [] [] emptyLHsBinds
+ (PrefixCon (map nlVarPat arg_ids)) record_in_ty]
+ rhs)
in
- mapDs mk_alt cons_to_upd `thenDs` \ alts ->
- mk_default `thenDs` \ deflt ->
+ -- Record stuff doesn't work for existentials
+ -- The type checker checks for this, but we need
+ -- worry only about the constructors that are to be updated
+ ASSERT2( all isVanillaDataCon cons_to_upd, ppr expr )
+
+ -- It's important to generate the match with matchWrapper,
+ -- and the right hand sides with applications of the wrapper Id
+ -- so that everything works when we are doing fancy unboxing on the
+ -- constructor aguments.
+ mappM mk_alt cons_to_upd `thenDs` \ alts ->
+ matchWrapper RecUpd (MatchGroup alts in_out_ty) `thenDs` \ ([discrim_var], matching_code) ->
- returnDs (Case record_expr' (AlgAlts alts deflt))
+ returnDs (bindNonRec discrim_var record_expr' matching_code)
where
- has_all_fields :: Id -> Bool
+ updated_fields :: [FieldLabel]
+ updated_fields = [ idName sel_id | (L _ sel_id,_) <- rbinds]
+
+ -- Get the type constructor from the record_in_ty
+ -- so that we are sure it'll have all its DataCons
+ -- (In GHCI, it's possible that some TyCons may not have all
+ -- their constructors, in a module-loop situation.)
+ tycon = tcTyConAppTyCon record_in_ty
+ data_cons = tyConDataCons tycon
+ cons_to_upd = filter has_all_fields data_cons
+
+ has_all_fields :: DataCon -> Bool
has_all_fields con_id
- = all ok rbinds
+ = all (`elem` con_fields) updated_fields
where
- con_fields = dataConFieldLabels con_id
- ok (sel_id, _, _) = recordSelectorFieldLabel sel_id `elem` con_fields
+ con_fields = dataConFieldLabels con_id
\end{code}
-Dictionary lambda and application
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+\noindent
+\underline{\bf 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 )
+ = dsLExpr expr `thenDs` \ 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
+ = dsLExpr expr `thenDs` \ core_expr ->
+ returnDs (foldl (\f d -> f `App` (Var d)) core_expr dicts)
+
+dsExpr (HsCoerce co_fn e) = dsCoercion co_fn (dsExpr e)
\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}
+Here is where we desugar the Template Haskell brackets and escapes
+
\begin{code}
-dsExpr (SingleDict dict) -- just a local
- = lookupEnvWithDefaultDs dict (Var dict)
+-- Template Haskell stuff
-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 ->
+#ifdef GHCI /* Only if bootstrapping */
+dsExpr (HsBracketOut x ps) = dsBracket x ps
+dsExpr (HsSpliceE s) = pprPanic "dsExpr:splice" (ppr s)
+#endif
- (case num_of_d_and_ms of
- 0 -> returnDs cocon_unit -- unit
+-- Arrow notation extension
+dsExpr (HsProc pat cmd) = dsProcExpr pat cmd
+\end{code}
- 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
+\begin{code}
#ifdef DEBUG
-- HsSyn constructs that just shouldn't be here:
-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).
+Desugar 'do' and 'mdo' expressions (NOT list comprehensions, they're
+handled in DsListComp). Basically does the translation given in the
+Haskell 98 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
+dsDo :: [LStmt Id]
+ -> LHsExpr Id
+ -> Type -- Type of the whole expression
+ -> DsM CoreExpr
- _ -> 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
- = let
- (ty_args, val_args) = foldr sep ([],[]) args
- in
- mkAppDs fun ty_args val_args
+dsDo stmts body result_ty
+ = go (map unLoc 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"
+ go [] = dsLExpr body
+
+ go (ExprStmt rhs then_expr _ : stmts)
+ = do { rhs2 <- dsLExpr rhs
+ ; then_expr2 <- dsExpr then_expr
+ ; rest <- go stmts
+ ; returnDs (mkApps then_expr2 [rhs2, rest]) }
+
+ go (LetStmt binds : stmts)
+ = do { rest <- go stmts
+ ; dsLocalBinds binds rest }
+
+ go (BindStmt pat rhs bind_op fail_op : stmts)
+ = do { body <- go stmts
+ ; var <- selectSimpleMatchVarL pat
+ ; match <- matchSinglePat (Var var) (StmtCtxt DoExpr) pat
+ result_ty (cantFailMatchResult body)
+ ; match_code <- handle_failure pat match fail_op
+ ; rhs' <- dsLExpr rhs
+ ; bind_op' <- dsExpr bind_op
+ ; returnDs (mkApps bind_op' [rhs', Lam var match_code]) }
+
+ -- In a do expression, pattern-match failure just calls
+ -- the monadic 'fail' rather than throwing an exception
+ handle_failure pat match fail_op
+ | matchCanFail match
+ = do { fail_op' <- dsExpr fail_op
+ ; fail_msg <- mkStringExpr (mk_fail_msg pat)
+ ; extractMatchResult match (App fail_op' fail_msg) }
+ | otherwise
+ = extractMatchResult match (error "It can't fail")
+
+mk_fail_msg pat = "Pattern match failure in do expression at " ++
+ showSDoc (ppr (getLoc pat))
\end{code}
+Translation for RecStmt's:
+-----------------------------
+We turn (RecStmt [v1,..vn] stmts) into:
+
+ (v1,..,vn) <- mfix (\~(v1,..vn). do stmts
+ return (v1,..vn))
\begin{code}
-dsRbinds :: TypecheckedRecordBinds -- The field bindings supplied
- -> ([(Id, CoreArg)] -> DsM CoreExpr) -- A continuation taking the field
- -- bindings with atomic rhss
- -> DsM CoreExpr -- The result of the continuation,
- -- wrapped in suitable Lets
-
-dsRbinds [] continue_with
- = continue_with []
-
-dsRbinds ((sel_id, rhs, pun_flag) : rbinds) continue_with
- = dsExpr rhs `thenDs` \ rhs' ->
- dsExprToAtom rhs' $ \ rhs_atom ->
- dsRbinds rbinds $ \ rbinds' ->
- continue_with ((panic "dsRbinds:field_label?"{-sel_id-}, rhs_atom) : rbinds')
-\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
+dsMDo :: PostTcTable
+ -> [LStmt Id]
+ -> LHsExpr Id
+ -> Type -- Type of the whole expression
+ -> DsM CoreExpr
+
+dsMDo tbl stmts body result_ty
+ = go (map unLoc stmts)
+ where
+ (m_ty, b_ty) = tcSplitAppTy result_ty -- result_ty must be of the form (m b)
+ mfix_id = lookupEvidence tbl mfixName
+ return_id = lookupEvidence tbl returnMName
+ bind_id = lookupEvidence tbl bindMName
+ then_id = lookupEvidence tbl thenMName
+ fail_id = lookupEvidence tbl failMName
+ ctxt = MDoExpr tbl
+
+ go [] = dsLExpr body
+
+ go (LetStmt binds : stmts)
+ = do { rest <- go stmts
+ ; dsLocalBinds binds rest }
+
+ go (ExprStmt rhs _ rhs_ty : stmts)
+ = do { rhs2 <- dsLExpr rhs
+ ; rest <- go stmts
+ ; returnDs (mkApps (Var then_id) [Type rhs_ty, Type b_ty, rhs2, rest]) }
+
+ go (BindStmt pat rhs _ _ : stmts)
+ = do { body <- go stmts
+ ; var <- selectSimpleMatchVarL pat
+ ; match <- matchSinglePat (Var var) (StmtCtxt ctxt) pat
+ result_ty (cantFailMatchResult body)
+ ; fail_msg <- mkStringExpr (mk_fail_msg pat)
+ ; let fail_expr = mkApps (Var fail_id) [Type b_ty, fail_msg]
+ ; match_code <- extractMatchResult match fail_expr
+
+ ; rhs' <- dsLExpr rhs
+ ; returnDs (mkApps (Var bind_id) [Type (hsPatType pat), Type b_ty,
+ rhs', Lam var match_code]) }
+
+ go (RecStmt rec_stmts later_ids rec_ids rec_rets binds : stmts)
+ = ASSERT( length rec_ids > 0 )
+ ASSERT( length rec_ids == length rec_rets )
+ go (new_bind_stmt : let_stmt : stmts)
+ where
+ new_bind_stmt = mkBindStmt (mk_tup_pat later_pats) mfix_app
+ let_stmt = LetStmt (HsValBinds (ValBindsOut [(Recursive, binds)] []))
+
+
+ -- Remove the later_ids that appear (without fancy coercions)
+ -- in rec_rets, because there's no need to knot-tie them separately
+ -- See Note [RecStmt] in HsExpr
+ later_ids' = filter (`notElem` mono_rec_ids) later_ids
+ mono_rec_ids = [ id | HsVar id <- rec_rets ]
+
+ mfix_app = nlHsApp (noLoc $ TyApp (nlHsVar mfix_id) [tup_ty]) mfix_arg
+ mfix_arg = noLoc $ HsLam (MatchGroup [mkSimpleMatch [mfix_pat] body]
+ (mkFunTy tup_ty body_ty))
+
+ -- The rec_tup_pat must bind the rec_ids only; remember that the
+ -- trimmed_laters may share the same Names
+ -- Meanwhile, the later_pats must bind the later_vars
+ rec_tup_pats = map mk_wild_pat later_ids' ++ map nlVarPat rec_ids
+ later_pats = map nlVarPat later_ids' ++ map mk_later_pat rec_ids
+ rets = map nlHsVar later_ids' ++ map noLoc rec_rets
+
+ mfix_pat = noLoc $ LazyPat $ mk_tup_pat rec_tup_pats
+ body = noLoc $ HsDo ctxt rec_stmts return_app body_ty
+ body_ty = mkAppTy m_ty tup_ty
+ tup_ty = mkCoreTupTy (map idType (later_ids' ++ rec_ids))
+ -- mkCoreTupTy deals with singleton case
+
+ return_app = nlHsApp (noLoc $ TyApp (nlHsVar return_id) [tup_ty])
+ (mk_ret_tup rets)
+
+ mk_wild_pat :: Id -> LPat Id
+ mk_wild_pat v = noLoc $ WildPat $ idType v
+
+ mk_later_pat :: Id -> LPat Id
+ mk_later_pat v | v `elem` later_ids' = mk_wild_pat v
+ | otherwise = nlVarPat v
+
+ mk_tup_pat :: [LPat Id] -> LPat Id
+ mk_tup_pat [p] = p
+ mk_tup_pat ps = noLoc $ mkVanillaTuplePat ps Boxed
+
+ mk_ret_tup :: [LHsExpr Id] -> LHsExpr Id
+ mk_ret_tup [r] = r
+ mk_ret_tup rs = noLoc $ ExplicitTuple rs Boxed
\end{code}
projects / ghc-hetmet.git / blobdiff