\section[DsExpr]{Matching expressions (Exprs)}
\begin{code}
-module DsExpr ( dsExpr, dsLet ) where
+module DsExpr ( dsExpr, dsLExpr, dsLet, dsLit ) where
#include "HsVersions.h"
-import HsSyn ( failureFreePat,
- HsExpr(..), OutPat(..), HsLit(..), ArithSeqInfo(..),
- Stmt(..), StmtCtxt(..), Match(..), HsBinds(..), MonoBinds(..),
- mkSimpleMatch
- )
-import TcHsSyn ( TypecheckedHsExpr, TypecheckedHsBinds,
- TypecheckedStmt,
- maybeBoxedPrimType
+import Match ( matchWrapper, matchSimply )
+import MatchLit ( dsLit )
+import DsBinds ( dsHsBinds, AutoScc(..) )
+import DsGRHSs ( dsGuarded )
+import DsListComp ( dsListComp, dsPArrComp )
+import DsUtils ( mkErrorAppDs, mkStringLit, mkConsExpr, mkNilExpr,
+ mkCoreTupTy, selectMatchVarL,
+ dsReboundNames, lookupReboundName )
+import DsArrows ( dsProcExpr )
+import DsMonad
- )
-import CoreSyn
+#ifdef GHCI
+ -- Template Haskell stuff iff bootstrapped
+import DsMeta ( dsBracket )
+#endif
-import DsMonad
-import DsBinds ( dsMonoBinds, AutoScc(..) )
-import DsGRHSs ( dsGuarded )
-import DsCCall ( dsCCall )
-import DsListComp ( dsListComp )
-import DsUtils ( mkErrorAppDs, mkDsLets, mkConsExpr, mkNilExpr )
-import Match ( matchWrapper, matchSimply )
+import HsSyn
+import TcHsSyn ( hsPatType )
-import CoreUtils ( coreExprType )
+-- 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, tcTyConAppArgs,
+ tcSplitTyConApp, isUnLiftedType, Type,
+ mkAppTy )
+import Type ( splitFunTys )
+import CoreSyn
+import CoreUtils ( exprType, mkIfThenElse, bindNonRec )
+
+import FieldLabel ( FieldLabel, fieldLabelTyCon )
import CostCentre ( mkUserCC )
-import FieldLabel ( FieldLabel )
-import Id ( Id, idType, recordSelectorFieldLabel )
-import Const ( Con(..) )
-import DataCon ( DataCon, dataConId, dataConTyCon, dataConArgTys, dataConFieldLabels )
-import Const ( mkMachInt, Literal(..), mkStrLit )
-import PrelInfo ( rEC_CON_ERROR_ID, rEC_UPD_ERROR_ID, iRREFUT_PAT_ERROR_ID )
-import TyCon ( isNewTyCon )
+import Id ( Id, idType, idName, recordSelectorFieldLabel )
+import PrelInfo ( rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID )
+import DataCon ( DataCon, dataConWrapId, dataConFieldLabels, dataConInstOrigArgTys )
import DataCon ( isExistentialDataCon )
-import Type ( splitFunTys, mkTyConApp,
- splitAlgTyConApp, splitTyConApp_maybe, isNotUsgTy, unUsgTy,
- splitAppTy, isUnLiftedType, Type
- )
-import TysWiredIn ( tupleCon, unboxedTupleCon,
- listTyCon, mkListTy,
- charDataCon, charTy, stringTy
- )
-import BasicTypes ( RecFlag(..) )
-import Maybes ( maybeToBool )
+import Name ( Name )
+import TyCon ( 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}
%* *
%************************************************************************
-@dsLet@ is a match-result transformer, taking the MatchResult for the body
+@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
-
+\begin{verbatim}
C x# = e
-
+\end{verbatim}
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 :: [HsBindGroup Id] -> CoreExpr -> DsM CoreExpr
+dsLet groups body = foldlDs dsBindGroup body (reverse groups)
-dsLet EmptyBinds body
- = returnDs body
+dsBindGroup :: CoreExpr -> HsBindGroup Id -> DsM CoreExpr
+dsBindGroup body (HsIPBinds binds)
+ = foldlDs dsIPBind body binds
+ where
+ dsIPBind body (L _ (IPBind n e))
+ = dsLExpr e `thenDs` \ e' ->
+ returnDs (Let (NonRec (ipNameName n) e') body)
-dsLet (ThenBinds b1 b2) body
- = dsLet b2 body `thenDs` \ body' ->
- dsLet b1 body'
-
-- 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 pragmas...
-dsLet (MonoBind (AbsBinds [] [] binder_triples inlines (PatMonoBind pat grhss loc)) sigs is_rec) body
- | or [isUnLiftedType (idType g) | (_, g, l) <- binder_triples]
+dsBindGroup body bind@(HsBindGroup hsbinds sigs is_rec)
+ | [L _ (AbsBinds [] [] exports inlines binds)] <- bagToList hsbinds,
+ or [isUnLiftedType (idType g) | (_, g, l) <- exports]
= ASSERT (case is_rec of {NonRecursive -> True; other -> False})
- putSrcLocDs loc $
- dsGuarded grhss `thenDs` \ rhs ->
+ -- Unlifted bindings are always non-recursive
+ -- and are always a Fun or Pat monobind
+ --
+ -- 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.)
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
+ body_w_exports = foldr bind_export body exports
+ bind_export (tvs, g, l) body = ASSERT( null tvs )
+ bindNonRec g (Var l) 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 (mkDsLets [NonRec b r | (b,r) <- prs] body)
-\end{code}
+ mk_error_app pat = mkErrorAppDs iRREFUT_PAT_ERROR_ID
+ (exprType body)
+ (showSDoc (ppr pat))
+ in
+ case bagToList binds of
+ [L loc (FunBind (L _ fun) _ matches)]
+ -> putSrcSpanDs loc $
+ matchWrapper (FunRhs (idName fun)) matches `thenDs` \ (args, rhs) ->
+ ASSERT( null args ) -- Functions aren't lifted
+ returnDs (bindNonRec fun rhs body_w_exports)
-%************************************************************************
-%* *
-\subsection[DsExpr-vars-and-cons]{Variables and constructors}
-%* *
-%************************************************************************
+ [L loc (PatBind pat grhss)]
+ -> putSrcSpanDs loc $
+ dsGuarded grhss `thenDs` \ rhs ->
+ mk_error_app pat `thenDs` \ error_expr ->
+ matchSimply rhs PatBindRhs pat body_w_exports error_expr
-\begin{code}
-dsExpr :: TypecheckedHsExpr -> DsM CoreExpr
+ other -> pprPanic "dsLet: unlifted" (ppr bind $$ ppr body)
-dsExpr e@(HsVar var) = returnDs (Var var)
-\end{code}
+-- Ordinary case for bindings
+dsBindGroup body (HsBindGroup binds sigs is_rec)
+ = dsHsBinds NoSccs binds [] `thenDs` \ prs ->
+ returnDs (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
+\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 (mkNilExpr charTy)
-
- | _LENGTH_ s == 1
- = let
- the_char = mkConApp charDataCon [mkLit (MachChar (_HEAD_ s))]
- the_nil = mkNilExpr charTy
- the_cons = mkConsExpr charTy the_char the_nil
- in
- 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] ->
- 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 (mkLit (NoRepStr str stringTy))
-
-dsExpr (HsLitOut (HsLitLit str) ty)
- | isUnLiftedType ty
- = returnDs (mkLit (MachLitLit str ty))
- | otherwise
- = 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, prim_ty)
- = case (maybeBoxedPrimType ty) of
- Just (boxing_data_con, prim_ty) -> (boxing_data_con, prim_ty)
- Nothing
- -> pprPanic "ERROR: ``literal-literal'' not a single-constructor type: "
- (hcat [ptext str, text "; type: ", ppr ty])
-
-dsExpr (HsLitOut (HsInt i) ty)
- = returnDs (mkLit (NoRepInteger i ty))
-
-dsExpr (HsLitOut (HsFrac r) ty)
- = returnDs (mkLit (NoRepRational r ty))
-
--- others where we know what to do:
+dsLExpr :: LHsExpr Id -> DsM CoreExpr
+dsLExpr (L loc e) = putSrcSpanDs loc $ dsExpr e
-dsExpr (HsLitOut (HsIntPrim i) _)
- | (i >= toInteger minInt && i <= toInteger maxInt)
- = returnDs (mkLit (mkMachInt i))
- | otherwise
- = error ("ERROR: Int constant " ++ show i ++ out_of_range_msg)
+dsExpr :: HsExpr Id -> DsM CoreExpr
-dsExpr (HsLitOut (HsFloatPrim f) _)
- = returnDs (mkLit (MachFloat f))
- -- ToDo: range checking needed!
-
-dsExpr (HsLitOut (HsDoublePrim d) _)
- = returnDs (mkLit (MachDouble d))
- -- ToDo: range checking needed!
-
-dsExpr (HsLitOut (HsChar c) _)
- = returnDs ( mkConApp charDataCon [mkLit (MachChar c)] )
-
-dsExpr (HsLitOut (HsCharPrim c) _)
- = returnDs (mkLit (MachChar c))
-
-dsExpr (HsLitOut (HsStringPrim s) _)
- = returnDs (mkLit (MachStr s))
-
--- end of literals magic. --
+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
+-- HsOverLit has been gotten rid of by the type checker
dsExpr expr@(HsLam a_Match)
- = matchWrapper LambdaMatch [a_Match] "lambda" `thenDs` \ (binders, matching_code) ->
+ = matchWrapper LambdaExpr [a_Match] `thenDs` \ (binders, matching_code) ->
returnDs (mkLams binders matching_code)
dsExpr expr@(HsApp fun arg)
- = dsExpr fun `thenDs` \ core_fun ->
- dsExpr arg `thenDs` \ core_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
\begin{code}
dsExpr (OpApp e1 op _ e2)
- = dsExpr op `thenDs` \ core_op ->
+ = dsLExpr op `thenDs` \ core_op ->
-- for the type of y, we need the type of op's 2nd argument
- dsExpr e1 `thenDs` \ x_core ->
- dsExpr e2 `thenDs` \ y_core ->
+ 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 ->
+ = dsLExpr 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)
+ (x_ty:y_ty:_, _) = splitFunTys (exprType core_op)
+ -- Must look through an implicit-parameter type;
+ -- newtype impossible; hence Type.splitFunTys
in
- dsExpr expr `thenDs` \ x_core ->
+ dsLExpr 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
+-- dsLExpr (SectionR op expr) -- \ x -> op x expr
dsExpr (SectionR op expr)
- = dsExpr op `thenDs` \ core_op ->
+ = dsLExpr op `thenDs` \ core_op ->
-- for the type of x, we need the type of op's 2nd argument
let
- (x_ty:y_ty:_, _) = splitFunTys (coreExprType core_op)
+ (x_ty:y_ty:_, _) = splitFunTys (exprType core_op)
+ -- See comment with SectionL
in
- dsExpr expr `thenDs` \ y_core ->
+ dsLExpr 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 ->
- dsCCall label core_args may_gc is_asm result_ty
- -- dsCCall does all the unboxification, etc.
-
dsExpr (HsSCC cc expr)
- = dsExpr expr `thenDs` \ core_expr ->
- getModuleAndGroupDs `thenDs` \ (mod_name, group_name) ->
- returnDs (Note (SCC (mkUserCC cc mod_name group_name)) core_expr)
+ = 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)
-- special case to handle unboxed tuple patterns.
-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) ->
+dsExpr (HsCase discrim matches)
+ | all ubx_tuple_match matches
+ = dsLExpr discrim `thenDs` \ core_discrim ->
+ matchWrapper CaseAlt matches `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))
+ _ -> panic ("dsLExpr: tuple pattern:\n" ++ showSDoc (ppr matching_code))
+ where
+ ubx_tuple_match (L _ (Match [L _ (TuplePat _ Unboxed)] _ _)) = True
+ ubx_tuple_match _ = False
-dsExpr (HsCase discrim matches src_loc)
- = putSrcLocDs src_loc $
- dsExpr discrim `thenDs` \ core_discrim ->
- matchWrapper CaseMatch matches "case" `thenDs` \ ([discrim_var], matching_code) ->
+dsExpr (HsCase discrim matches)
+ = dsLExpr discrim `thenDs` \ core_discrim ->
+ matchWrapper CaseAlt matches `thenDs` \ ([discrim_var], matching_code) ->
returnDs (bindNonRec discrim_var core_discrim matching_code)
dsExpr (HsLet binds body)
- = dsExpr body `thenDs` \ body' ->
+ = dsLExpr 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
+
+-- 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 _ result_ty)
= -- Special case for list comprehensions
- putSrcLocDs src_loc $
dsListComp stmts elt_ty
+ where
+ (_, [elt_ty]) = tcSplitTyConApp result_ty
- | otherwise
- = putSrcLocDs src_loc $
- dsDo do_or_lc stmts return_id then_id fail_id result_ty
+dsExpr (HsDo do_or_lc stmts ids result_ty)
+ | isDoExpr do_or_lc
+ = dsDo do_or_lc stmts ids result_ty
+
+dsExpr (HsDo PArrComp stmts _ result_ty)
+ = -- Special case for array comprehensions
+ dsPArrComp (map unLoc stmts) elt_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 ->
+ (_, [elt_ty]) = tcSplitTyConApp 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 ->
+ = dsLExpr expr `thenDs` \ core_expr ->
returnDs (mkLams tyvars core_expr)
dsExpr (TyApp expr tys)
- = dsExpr expr `thenDs` \ core_expr ->
+ = 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)
+dsExpr (ExplicitList ty xs)
= go xs
where
- list_ty = mkListTy ty
-
go [] = returnDs (mkNilExpr ty)
- go (x:xs) = dsExpr x `thenDs` \ core_x ->
+ go (x:xs) = dsLExpr x `thenDs` \ core_x ->
go xs `thenDs` \ core_xs ->
- ASSERT( isNotUsgTy ty )
returnDs (mkConsExpr 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 . unUsgTy . coreExprType) core_exprs ++ core_exprs))
- -- the above unUsgTy is *required* -- KSW 1999-04-07
-
-dsExpr (HsCon con_id [ty] [arg])
- | isNewTyCon tycon
- = dsExpr arg `thenDs` \ arg' ->
- returnDs (Note (Coerce result_ty (unUsgTy (coreExprType arg'))) arg')
- where
- result_ty = mkTyConApp tycon [ty]
- tycon = dataConTyCon con_id
-
-dsExpr (HsCon con_id tys args)
- = mapDs dsExpr args `thenDs` \ args2 ->
- ASSERT( all isNotUsgTy tys )
- returnDs (mkConApp con_id (map Type tys ++ args2))
+-- 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 (ArithSeqOut expr (From from))
- = dsExpr expr `thenDs` \ expr2 ->
- dsExpr from `thenDs` \ from2 ->
+ = dsLExpr expr `thenDs` \ expr2 ->
+ dsLExpr from `thenDs` \ from2 ->
returnDs (App expr2 from2)
dsExpr (ArithSeqOut expr (FromTo from two))
- = dsExpr expr `thenDs` \ expr2 ->
- dsExpr from `thenDs` \ from2 ->
- dsExpr two `thenDs` \ two2 ->
+ = dsLExpr expr `thenDs` \ expr2 ->
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr two `thenDs` \ two2 ->
returnDs (mkApps expr2 [from2, two2])
dsExpr (ArithSeqOut expr (FromThen from thn))
- = dsExpr expr `thenDs` \ expr2 ->
- dsExpr from `thenDs` \ from2 ->
- dsExpr thn `thenDs` \ thn2 ->
+ = dsLExpr expr `thenDs` \ expr2 ->
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr thn `thenDs` \ 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 ->
+ = dsLExpr expr `thenDs` \ expr2 ->
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr thn `thenDs` \ thn2 ->
+ dsLExpr two `thenDs` \ two2 ->
returnDs (mkApps expr2 [from2, thn2, two2])
+
+dsExpr (PArrSeqOut expr (FromTo from two))
+ = dsLExpr expr `thenDs` \ expr2 ->
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr two `thenDs` \ two2 ->
+ returnDs (mkApps expr2 [from2, two2])
+
+dsExpr (PArrSeqOut expr (FromThenTo from thn two))
+ = dsLExpr expr `thenDs` \ expr2 ->
+ dsLExpr from `thenDs` \ from2 ->
+ dsLExpr thn `thenDs` \ thn2 ->
+ dsLExpr two `thenDs` \ two2 ->
+ returnDs (mkApps expr2 [from2, thn2, two2])
+
+dsExpr (PArrSeqOut 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 (RecordConOut data_con con_expr rbinds)
- = dsExpr con_expr `thenDs` \ con_expr' ->
+ = dsLExpr con_expr `thenDs` \ con_expr' ->
let
- (arg_tys, _) = splitFunTys (coreExprType con_expr')
+ (arg_tys, _) = tcSplitFunTys (exprType con_expr')
+ -- A newtype in the corner should be opaque;
+ -- hence TcType.tcSplitFunTys
mk_arg (arg_ty, lbl)
- = case [rhs | (sel_id,rhs,_) <- rbinds,
+ = case [rhs | (L _ sel_id, rhs) <- rbinds,
lbl == recordSelectorFieldLabel sel_id] of
(rhs:rhss) -> ASSERT( null rhss )
- dsExpr rhs
+ 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 data_con
in
- mapDs mk_arg (zipEqual "dsExpr:RecordCon" arg_tys (dataConFieldLabels data_con)) `thenDs` \ con_args ->
+
+ (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, 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 record_out_ty dicts rbinds)
- = dsExpr record_expr `thenDs` \ record_expr' ->
+dsExpr (RecordUpdOut record_expr record_in_ty record_out_ty [])
+ = dsLExpr record_expr
+
+dsExpr expr@(RecordUpdOut record_expr record_in_ty record_out_ty rbinds)
+ = dsLExpr 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
-
+ in_inst_tys = tcTyConAppArgs record_in_ty -- Newtype opaque
+ out_inst_tys = tcTyConAppArgs record_out_ty -- Newtype opaque
+
mk_val_arg field old_arg_id
- = case [rhs | (f, rhs) <- rbinds', field == f] of
+ = case [rhs | (L _ sel_id, rhs) <- rbinds,
+ field == recordSelectorFieldLabel sel_id] of
(rhs:rest) -> ASSERT(null rest) rhs
- [] -> Var old_arg_id
+ [] -> nlHsVar old_arg_id
mk_alt con
- = newSysLocalsDs (dataConArgTys con in_inst_tys) `thenDs` \ arg_ids ->
+ = newSysLocalsDs (dataConInstOrigArgTys con in_inst_tys) `thenDs` \ arg_ids ->
+ -- This call to dataConArgTys won't work for existentials
let
val_args = zipWithEqual "dsExpr:RecordUpd" mk_val_arg
(dataConFieldLabels con) arg_ids
- rhs = mkApps (mkApps (Var (dataConId con)) initial_args) val_args
+ rhs = foldl (\a b -> nlHsApp a b)
+ (noLoc $ TyApp (nlHsVar (dataConWrapId con))
+ out_inst_tys)
+ 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)]
+ returnDs (mkSimpleMatch [noLoc $ ConPatOut con (PrefixCon (map nlVarPat arg_ids)) record_in_ty [] []]
+ rhs
+ record_out_ty)
in
-- Record stuff doesn't work for existentials
- ASSERT( all (not . isExistentialDataCon) cons )
+ -- The type checker checks for this, but we need
+ -- worry only about the constructors that are to be updated
+ ASSERT2( all (not . isExistentialDataCon) 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 alts `thenDs` \ ([discrim_var], matching_code) ->
- newSysLocalDs record_in_ty `thenDs` \ case_bndr ->
- mapDs mk_alt cons_to_upd `thenDs` \ alts ->
- mk_default `thenDs` \ deflt ->
+ returnDs (bindNonRec discrim_var record_expr' matching_code)
- returnDs (Case record_expr' case_bndr (alts ++ deflt))
where
+ updated_fields :: [FieldLabel]
+ updated_fields = [ recordSelectorFieldLabel sel_id
+ | (L _ sel_id,_) <- rbinds]
+
+ -- Get the type constructor from the first field label,
+ -- 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 = fieldLabelTyCon (head updated_fields)
+ 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 ->
+ = dsLExpr expr `thenDs` \ core_expr ->
returnDs (mkLams dictvars core_expr)
------------------
dsExpr (DictApp expr dicts) -- becomes a curried application
- = dsExpr expr `thenDs` \ core_expr ->
+ = dsLExpr expr `thenDs` \ core_expr ->
returnDs (foldl (\f d -> f `App` (Var d)) core_expr dicts)
\end{code}
+Here is where we desugar the Template Haskell brackets and escapes
+
+\begin{code}
+-- Template Haskell stuff
+
+#ifdef GHCI /* Only if bootstrapping */
+dsExpr (HsBracketOut x ps) = dsBracket x ps
+dsExpr (HsSpliceE s) = pprPanic "dsExpr:splice" (ppr s)
+#endif
+
+-- Arrow notation extension
+dsExpr (HsProc pat cmd) = dsProcExpr pat cmd
+\end{code}
+
+
\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"
+dsExpr (PArrSeqIn _) = panic "dsExpr:PArrSeqIn"
#endif
-out_of_range_msg -- ditto
- = " out of range: [" ++ show minInt ++ ", " ++ show maxInt ++ "]\n"
\end{code}
%--------------------------------------------------------------------
-Basically does the translation given in the Haskell~1.3 report:
+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}
-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)
+dsDo :: HsStmtContext Name
+ -> [LStmt Id]
+ -> ReboundNames Id -- id for: [return,fail,>>=,>>] and possibly mfixName
+ -> 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
- (_, b_ty) = splitAppTy result_ty -- result_ty must be of the form (m b)
+dsDo do_or_lc stmts ids result_ty
+ = dsReboundNames ids `thenDs` \ (meth_binds, ds_meths) ->
+ let
+ return_id = lookupReboundName ds_meths returnMName
+ fail_id = lookupReboundName ds_meths failMName
+ bind_id = lookupReboundName ds_meths bindMName
+ then_id = lookupReboundName ds_meths thenMName
+
+ (m_ty, b_ty) = tcSplitAppTy 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 = ASSERT( isNotUsgTy b_ty )
- "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])
+ -- For ExprStmt, see the comments near HsExpr.Stmt about
+ -- exactly what ExprStmts mean!
+ --
+ -- In dsDo we can only see DoStmt and ListComp (no guards)
+
+ go [ResultStmt expr] = dsLExpr expr
+
+
+ go (ExprStmt expr a_ty : stmts)
+ = dsLExpr expr `thenDs` \ expr2 ->
+ go stmts `thenDs` \ rest ->
+ returnDs (mkApps then_id [Type a_ty, Type b_ty, expr2, rest])
- go (LetStmt binds : stmts )
+ go (LetStmt binds : stmts)
= go stmts `thenDs` \ rest ->
dsLet binds rest
- go (BindStmt pat expr locn : stmts)
- = putSrcLocDs locn $
- dsExpr expr `thenDs` \ expr2 ->
+ go (BindStmt pat expr : stmts)
+ = go stmts `thenDs` \ body ->
+ dsLExpr expr `thenDs` \ rhs ->
+ mkStringLit (mk_msg (getLoc pat)) `thenDs` \ core_msg ->
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 = ASSERT2( isNotUsgTy a_ty, ppr a_ty )
- ASSERT2( isNotUsgTy b_ty, ppr b_ty )
- "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 a do expression, pattern-match failure just calls
+ -- the monadic 'fail' rather than throwing an exception
+ fail_expr = mkApps fail_id [Type b_ty, core_msg]
+ a_ty = hsPatType pat
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])
+ selectMatchVarL pat `thenDs` \ var ->
+ matchSimply (Var var) (StmtCtxt do_or_lc) pat
+ body fail_expr `thenDs` \ match_code ->
+ returnDs (mkApps bind_id [Type a_ty, Type b_ty, rhs, Lam var match_code])
+
+ go (RecStmt rec_stmts later_vars rec_vars rec_rets : stmts)
+ = go (bind_stmt : stmts)
+ where
+ bind_stmt = dsRecStmt m_ty ds_meths rec_stmts later_vars rec_vars rec_rets
+
in
- go stmts
+ go (map unLoc stmts) `thenDs` \ stmts_code ->
+ returnDs (foldr Let stmts_code meth_binds)
where
- do_expr expr locn = putSrcLocDs locn (dsExpr expr)
-
- match_msg = case do_or_lc of
- DoStmt -> "`do' statement"
- ListComp -> "comprehension"
+ mk_msg locn = "Pattern match failure in do expression at " ++ showSDoc (ppr locn)
\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}
-var_pat (WildPat _) = True
-var_pat (VarPat _) = True
-var_pat _ = False
+dsRecStmt :: Type -- Monad type constructor :: * -> *
+ -> [(Name,Id)] -- Rebound Ids
+ -> [LStmt Id]
+ -> [Id] -> [Id] -> [LHsExpr Id]
+ -> Stmt Id
+dsRecStmt m_ty ds_meths stmts later_vars rec_vars rec_rets
+ = ASSERT( length vars == length rets )
+ BindStmt tup_pat mfix_app
+ where
+ vars@(var1:rest) = later_vars ++ rec_vars -- Always at least one
+ rets@(ret1:_) = map nlHsVar later_vars ++ rec_rets
+ one_var = null rest
+
+ mfix_app = nlHsApp (noLoc $ TyApp (nlHsVar mfix_id) [tup_ty]) mfix_arg
+ mfix_arg = noLoc $ HsLam (mkSimpleMatch [tup_pat] body tup_ty)
+
+ tup_expr | one_var = ret1
+ | otherwise = noLoc $ ExplicitTuple rets Boxed
+ tup_ty = mkCoreTupTy (map idType vars)
+ -- Deals with singleton case
+ tup_pat | one_var = nlVarPat var1
+ | otherwise = noLoc $ LazyPat (noLoc $ TuplePat (map nlVarPat vars) Boxed)
+
+ body = noLoc $ HsDo DoExpr (stmts ++ [return_stmt])
+ [(n, HsVar id) | (n,id) <- ds_meths] -- A bit of a hack
+ (mkAppTy m_ty tup_ty)
+
+ Var return_id = lookupReboundName ds_meths returnMName
+ Var mfix_id = lookupReboundName ds_meths mfixName
+
+ return_stmt = noLoc $ ResultStmt return_app
+ return_app = nlHsApp (noLoc $ TyApp (nlHsVar return_id) [tup_ty]) tup_expr
\end{code}
-