+++ /dev/null
-%
-% (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"
-#if defined(GHCI) && defined(BREAKPOINT)
-import Foreign.StablePtr ( newStablePtr, castStablePtrToPtr )
-import GHC.Exts ( Ptr(..), Int(..), addr2Int# )
-import IOEnv ( ioToIOEnv )
-import PrelNames ( breakpointJumpName )
-import TysWiredIn ( unitTy )
-import TypeRep ( Type(..) )
-#endif
-
-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 HsSyn
-import TcHsSyn ( hsPatType, mkVanillaTuplePat )
-
--- 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 CostCentre ( mkUserCC )
-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}
-
-
-%************************************************************************
-%* *
- dsLocalBinds, dsValBinds
-%* *
-%************************************************************************
-
-\begin{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-vars-and-cons]{Variables, constructors, literals}
-%* *
-%************************************************************************
-
-\begin{code}
-dsLExpr :: LHsExpr Id -> DsM CoreExpr
-dsLExpr (L loc e) = putSrcSpanDs loc $ dsExpr e
-
-dsExpr :: HsExpr Id -> DsM CoreExpr
-
-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 (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 LambdaExpr a_Match `thenDs` \ (binders, matching_code) ->
- returnDs (mkLams binders matching_code)
-
-#if defined(GHCI) && defined(BREAKPOINT)
-dsExpr (HsApp (L _ (HsApp realFun@(L _ (HsCoerce _ fun)) (L loc arg))) _)
- | HsVar funId <- fun
- , idName funId == breakpointJumpName
- , ids <- filter (not.hasTyVar.idType) (extractIds arg)
- = do dsWarn (text "Extracted ids:" <+> ppr ids <+> ppr (map idType ids))
- stablePtr <- ioToIOEnv $ newStablePtr ids
- -- Yes, I know... I'm gonna burn in hell.
- let Ptr addr# = castStablePtrToPtr stablePtr
- funCore <- dsLExpr realFun
- argCore <- dsLExpr (L loc (HsLit (HsInt (fromIntegral (I# (addr2Int# addr#))))))
- hvalCore <- dsLExpr (L loc (extractHVals ids))
- return ((funCore `App` argCore) `App` hvalCore)
- where extractIds :: HsExpr Id -> [Id]
- extractIds (HsApp fn arg)
- | HsVar argId <- unLoc arg
- = argId:extractIds (unLoc fn)
- | TyApp arg' ts <- unLoc arg
- , HsVar argId <- unLoc arg'
- = error (showSDoc (ppr ts)) -- argId:extractIds (unLoc fn)
- extractIds x = []
- extractHVals ids = ExplicitList unitTy (map (L loc . HsVar) ids)
- hasTyVar (TyVarTy _) = True
- hasTyVar (FunTy a b) = hasTyVar a || hasTyVar b
- hasTyVar (NoteTy _ t) = hasTyVar t
- hasTyVar (AppTy a b) = hasTyVar a || hasTyVar b
- hasTyVar (TyConApp _ ts) = any hasTyVar ts
- hasTyVar _ = False
-#endif
-
-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
-\begin{verbatim}
- (expr op)
-\end{verbatim}
-to
-\begin{verbatim}
- \x -> op expr x
-\end{verbatim}
-
-But no! expr might be a redex, and we can lose laziness badly this
-way. Consider
-\begin{verbatim}
- map (expr op) xs
-\end{verbatim}
-for example. So we convert instead to
-\begin{verbatim}
- let y = expr in \x -> op y x
-\end{verbatim}
-If \tr{expr} is actually just a variable, say, then the simplifier
-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)
- = 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 (exprType core_op)
- -- Must look through an implicit-parameter type;
- -- newtype impossible; hence Type.splitFunTys
- in
- 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]))
-
--- 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:y_ty:_, _) = splitFunTys (exprType core_op)
- -- See comment with SectionL
- in
- 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 (HsSCC cc 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)
-
-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}
-
-
-\noindent
-\underline{\bf Type lambda and application}
-% ~~~~~~~~~~~~~~~~~~~~~~~~~~~
-\begin{code}
-dsExpr (TyLam tyvars expr)
- = dsLExpr expr `thenDs` \ core_expr ->
- returnDs (mkLams tyvars core_expr)
-
-dsExpr (TyApp expr tys)
- = dsLExpr expr `thenDs` \ core_expr ->
- returnDs (mkTyApps core_expr tys)
-\end{code}
-
-
-\noindent
-\underline{\bf Various data construction things}
-% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-\begin{code}
-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 ->
- dsLExpr from `thenDs` \ from2 ->
- dsLExpr two `thenDs` \ two2 ->
- returnDs (mkApps expr2 [from2, two2])
-
-dsExpr (ArithSeq expr (FromThen from thn))
- = dsExpr expr `thenDs` \ expr2 ->
- dsLExpr from `thenDs` \ from2 ->
- dsLExpr thn `thenDs` \ thn2 ->
- returnDs (mkApps expr2 [from2, thn2])
-
-dsExpr (ArithSeq 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 (FromTo from two))
- = dsExpr expr `thenDs` \ expr2 ->
- 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}
-
-\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")
-\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 (L _ data_con_id) con_expr rbinds)
- = dsExpr con_expr `thenDs` \ con_expr' ->
- let
- (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
-
- (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
- case r of
- T1 op1 _ op3 -> T1 op1 op2 op3
- T2 op4 _ -> T2 op4 op2
- other -> recUpdError "M.lhs/230"
-\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 (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
-
- let
- 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 (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 = 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 (mkSimpleMatch [noLoc $ ConPatOut (noLoc con) [] [] emptyLHsBinds
- (PrefixCon (map nlVarPat arg_ids)) record_in_ty]
- rhs)
- in
- -- 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 (bindNonRec discrim_var record_expr' matching_code)
-
- where
- 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 (`elem` con_fields) updated_fields
- where
- con_fields = dataConFieldLabels con_id
-\end{code}
-
-
-\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)
- = dsLExpr expr `thenDs` \ core_expr ->
- returnDs (mkLams dictvars core_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}
-
-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 (ExprWithTySig _ _) = panic "dsExpr:ExprWithTySig"
-#endif
-
-\end{code}
-
-%--------------------------------------------------------------------
-
-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 :: [LStmt Id]
- -> LHsExpr Id
- -> Type -- Type of the whole expression
- -> DsM CoreExpr
-
-dsDo stmts body result_ty
- = go (map unLoc stmts)
- where
- 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}
-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