%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[DsUtils]{Utilities for desugaring}
CanItFail(..), EquationInfo(..), MatchResult(..),
EqnNo, EqnSet,
- combineGRHSMatchResults,
- combineMatchResults,
- dsExprToAtomGivenTy, DsCoreArg,
- mkCoAlgCaseMatchResult,
- mkAppDs, mkConDs, mkPrimDs, mkErrorAppDs,
- mkCoLetsMatchResult,
- mkCoPrimCaseMatchResult,
- mkFailurePair,
- mkGuardedMatchResult,
- mkSelectorBinds,
- mkTupleExpr,
- mkTupleSelector,
- selectMatchVars,
- showForErr
+ cantFailMatchResult, extractMatchResult,
+ combineMatchResults,
+ adjustMatchResult, adjustMatchResultDs,
+ mkCoLetsMatchResult, mkGuardedMatchResult,
+ mkCoPrimCaseMatchResult, mkCoAlgCaseMatchResult,
+
+ mkErrorAppDs,
+
+ mkSelectorBinds, mkTupleExpr, mkTupleSelector,
+
+ selectMatchVar
) where
#include "HsVersions.h"
import {-# SOURCE #-} Match ( matchSimply )
-import HsSyn ( OutPat(..), Stmt, DoOrListComp )
+import HsSyn ( OutPat(..) )
import TcHsSyn ( TypecheckedPat )
import DsHsSyn ( outPatType, collectTypedPatBinders )
import CoreSyn
import DsMonad
-import CoreUtils ( coreExprType, mkCoreIfThenElse )
-import PrelVals ( iRREFUT_PAT_ERROR_ID, voidId )
-import Id ( idType, dataConArgTys,
- DataCon, Id, GenId )
-import Literal ( Literal(..) )
-import PrimOp ( PrimOp )
+import CoreUtils ( coreExprType )
+import PrelVals ( iRREFUT_PAT_ERROR_ID )
+import Id ( idType, Id, mkWildId )
+import Const ( Literal(..), Con(..) )
import TyCon ( isNewTyCon, tyConDataCons )
-import Type ( mkRhoTy, mkFunTy,
- isUnpointedType, mkTyConApp, splitAlgTyConApp,
+import DataCon ( DataCon )
+import Type ( mkFunTy, isUnLiftedType, splitAlgTyConApp,
Type
)
-import BasicTypes ( Unused )
-import TysPrim ( voidTy )
-import TysWiredIn ( unitDataCon, tupleCon, stringTy )
-import UniqSet ( mkUniqSet, minusUniqSet, uniqSetToList, UniqSet )
-import Unique ( Unique )
+import TysWiredIn ( unitDataCon, tupleCon, stringTy, unitTy, unitDataCon )
+import UniqSet ( mkUniqSet, minusUniqSet, isEmptyUniqSet, UniqSet )
import Outputable
\end{code}
otherwise, make one up.
\begin{code}
-selectMatchVars :: [TypecheckedPat] -> DsM [Id]
-selectMatchVars pats
- = mapDs var_from_pat_maybe pats
- where
- var_from_pat_maybe (VarPat var) = returnDs var
- var_from_pat_maybe (AsPat var pat) = returnDs var
- var_from_pat_maybe (LazyPat pat) = var_from_pat_maybe pat
- var_from_pat_maybe other_pat
- = newSysLocalDs (outPatType other_pat) -- OK, better make up one...
+selectMatchVar :: TypecheckedPat -> DsM Id
+selectMatchVar (VarPat var) = returnDs var
+selectMatchVar (AsPat var pat) = returnDs var
+selectMatchVar (LazyPat pat) = selectMatchVar pat
+selectMatchVar other_pat = newSysLocalDs (outPatType other_pat) -- OK, better make up one...
\end{code}
data EquationInfo
= EqnInfo
- EqnNo -- The number of the equation
+ EqnNo -- The number of the equation
+
DsMatchContext -- The context info is used when producing warnings
-- about shadowed patterns. It's the context
-- of the *first* thing matched in this group.
-- Should perhaps be a list of them all!
- [TypecheckedPat] -- the patterns for an eqn
+
+ [TypecheckedPat] -- The patterns for an eqn
+
MatchResult -- Encapsulates the guards and bindings
\end{code}
\begin{code}
data MatchResult
= MatchResult
- CanItFail
- Type -- Type of argument expression
-
- (CoreExpr -> CoreExpr)
+ CanItFail -- Tells whether the failure expression is used
+ (CoreExpr -> DsM CoreExpr)
-- Takes a expression to plug in at the
-- failure point(s). The expression should
-- be duplicatable!
orFail CantFail CantFail = CantFail
orFail _ _ = CanFail
+\end{code}
+
+Functions on MatchResults
+
+\begin{code}
+cantFailMatchResult :: CoreExpr -> MatchResult
+cantFailMatchResult expr = MatchResult CantFail (\ ignore -> returnDs expr)
+extractMatchResult :: MatchResult -> CoreExpr -> DsM CoreExpr
+extractMatchResult (MatchResult CantFail match_fn) fail_expr
+ = match_fn (error "It can't fail!")
-mkCoLetsMatchResult :: [CoreBinding] -> MatchResult -> MatchResult
-mkCoLetsMatchResult binds (MatchResult can_it_fail ty body_fn)
- = MatchResult can_it_fail ty (\body -> mkCoLetsAny binds (body_fn body))
+extractMatchResult (MatchResult CanFail match_fn) fail_expr
+ = mkFailurePair fail_expr `thenDs` \ (fail_bind, if_it_fails) ->
+ match_fn if_it_fails `thenDs` \ body ->
+ returnDs (Let fail_bind body)
-mkGuardedMatchResult :: CoreExpr -> MatchResult -> DsM MatchResult
-mkGuardedMatchResult pred_expr (MatchResult can_it_fail ty body_fn)
- = returnDs (MatchResult CanFail
- ty
- (\fail -> mkCoreIfThenElse pred_expr (body_fn fail) fail)
- )
+
+combineMatchResults :: MatchResult -> MatchResult -> MatchResult
+combineMatchResults (MatchResult CanFail body_fn1)
+ (MatchResult can_it_fail2 body_fn2)
+ = MatchResult can_it_fail2 body_fn
+ where
+ body_fn fail = body_fn2 fail `thenDs` \ body2 ->
+ mkFailurePair body2 `thenDs` \ (fail_bind, duplicatable_expr) ->
+ body_fn1 duplicatable_expr `thenDs` \ body1 ->
+ returnDs (Let fail_bind body1)
+
+combineMatchResults match_result1@(MatchResult CantFail body_fn1) match_result2
+ = match_result1
+
+
+adjustMatchResult :: (CoreExpr -> CoreExpr) -> MatchResult -> MatchResult
+adjustMatchResult encl_fn (MatchResult can_it_fail body_fn)
+ = MatchResult can_it_fail (\fail -> body_fn fail `thenDs` \ body ->
+ returnDs (encl_fn body))
+
+adjustMatchResultDs :: (CoreExpr -> DsM CoreExpr) -> MatchResult -> MatchResult
+adjustMatchResultDs encl_fn (MatchResult can_it_fail body_fn)
+ = MatchResult can_it_fail (\fail -> body_fn fail `thenDs` \ body ->
+ encl_fn body)
+
+
+mkCoLetsMatchResult :: [CoreBind] -> MatchResult -> MatchResult
+mkCoLetsMatchResult binds match_result
+ = adjustMatchResult (mkLets binds) match_result
+
+
+mkGuardedMatchResult :: CoreExpr -> MatchResult -> MatchResult
+mkGuardedMatchResult pred_expr (MatchResult can_it_fail body_fn)
+ = MatchResult CanFail (\fail -> body_fn fail `thenDs` \ body ->
+ returnDs (mkIfThenElse pred_expr body fail))
mkCoPrimCaseMatchResult :: Id -- Scrutinee
- -> [(Literal, MatchResult)] -- Alternatives
- -> DsM MatchResult
-mkCoPrimCaseMatchResult var alts
- = newSysLocalDs (idType var) `thenDs` \ wild ->
- returnDs (MatchResult CanFail
- ty1
- (mk_case alts wild))
+ -> [(Literal, MatchResult)] -- Alternatives
+ -> MatchResult
+mkCoPrimCaseMatchResult var match_alts
+ = MatchResult CanFail mk_case
where
- ((_,MatchResult _ ty1 _) : _) = alts
+ mk_case fail
+ = mapDs (mk_alt fail) match_alts `thenDs` \ alts ->
+ returnDs (Case (Var var) var (alts ++ [(DEFAULT, [], fail)]))
- mk_case alts wild fail_expr
- = Case (Var var) (PrimAlts final_alts (BindDefault wild fail_expr))
- where
- final_alts = [ (lit, body_fn fail_expr)
- | (lit, MatchResult _ _ body_fn) <- alts
- ]
+ mk_alt fail (lit, MatchResult _ body_fn) = body_fn fail `thenDs` \ body ->
+ returnDs (Literal lit, [], body)
-mkCoAlgCaseMatchResult :: Id -- Scrutinee
- -> [(DataCon, [Id], MatchResult)] -- Alternatives
- -> DsM MatchResult
+mkCoAlgCaseMatchResult :: Id -- Scrutinee
+ -> [(DataCon, [CoreBndr], MatchResult)] -- Alternatives
+ -> MatchResult
-mkCoAlgCaseMatchResult var alts
- | isNewTyCon tycon -- newtype case; use a let
+mkCoAlgCaseMatchResult var match_alts
+ | isNewTyCon tycon -- Newtype case; use a let
= ASSERT( newtype_sanity )
- returnDs (mkCoLetsMatchResult [coercion_bind] match_result)
-
- | otherwise -- datatype case
- = -- Find all the constructors in the type which aren't
- -- explicitly mentioned in the alternatives:
- case un_mentioned_constructors of
- [] -> -- All constructors mentioned, so no default needed
- returnDs (MatchResult can_any_alt_fail
- ty1
- (mk_case alts (\ignore -> NoDefault)))
-
- [con] -> -- Just one constructor missing, so add a case for it
- -- We need to build new locals for the args of the constructor,
- -- and figuring out their types is somewhat tiresome.
- let
- arg_tys = dataConArgTys con tycon_arg_tys
- in
- newSysLocalsDs arg_tys `thenDs` \ arg_ids ->
-
- -- Now we are ready to construct the new alternative
- let
- new_alt = (con, arg_ids, MatchResult CanFail ty1 id)
- in
- returnDs (MatchResult CanFail
- ty1
- (mk_case (new_alt:alts) (\ignore -> NoDefault)))
-
- other -> -- Many constructors missing, so use a default case
- newSysLocalDs scrut_ty `thenDs` \ wild ->
- returnDs (MatchResult CanFail
- ty1
- (mk_case alts (\fail_expr -> BindDefault wild fail_expr)))
+ mkCoLetsMatchResult [coercion_bind] match_result
+
+ | otherwise -- Datatype case; use a case
+ = MatchResult fail_flag mk_case
where
-- Common stuff
scrut_ty = idType var
(tycon, tycon_arg_tys, _) = splitAlgTyConApp scrut_ty
-- Stuff for newtype
- (con_id, arg_ids, match_result) = head alts
+ (con_id, arg_ids, match_result) = head match_alts
arg_id = head arg_ids
coercion_bind = NonRec arg_id (Note (Coerce (idType arg_id) scrut_ty) (Var var))
- newtype_sanity = null (tail alts) && null (tail arg_ids)
+ newtype_sanity = null (tail match_alts) && null (tail arg_ids)
-- Stuff for data types
data_cons = tyConDataCons tycon
- un_mentioned_constructors
- = uniqSetToList (mkUniqSet data_cons `minusUniqSet` mkUniqSet [ con | (con, _, _) <- alts] )
-
- match_results = [match_result | (_,_,match_result) <- alts]
- (MatchResult _ ty1 _ : _) = match_results
- can_any_alt_fail = foldr1 orFail [can_it_fail | MatchResult can_it_fail _ _ <- match_results]
+ match_results = [match_result | (_,_,match_result) <- match_alts]
- mk_case alts deflt_fn fail_expr
- = Case (Var var) (AlgAlts final_alts (deflt_fn fail_expr))
- where
- final_alts = [ (con, args, body_fn fail_expr)
- | (con, args, MatchResult _ _ body_fn) <- alts
- ]
+ fail_flag | exhaustive_case
+ = foldr1 orFail [can_it_fail | MatchResult can_it_fail _ <- match_results]
+ | otherwise
+ = CanFail
+ wild_var = mkWildId (idType var)
+ mk_case fail = mapDs (mk_alt fail) match_alts `thenDs` \ alts ->
+ returnDs (Case (Var var) wild_var (alts ++ mk_default fail))
-combineMatchResults :: MatchResult -> MatchResult -> DsM MatchResult
-combineMatchResults (MatchResult CanFail ty1 body_fn1)
- (MatchResult can_it_fail2 ty2 body_fn2)
- = mkFailurePair ty1 `thenDs` \ (bind_fn, duplicatable_expr) ->
- let
- new_body_fn1 = \body1 -> Let (bind_fn body1) (body_fn1 duplicatable_expr)
- new_body_fn2 = \body2 -> new_body_fn1 (body_fn2 body2)
- in
- returnDs (MatchResult can_it_fail2 ty1 new_body_fn2)
+ mk_alt fail (con, args, MatchResult _ body_fn)
+ = body_fn fail `thenDs` \ body ->
+ returnDs (DataCon con, args, body)
-combineMatchResults match_result1@(MatchResult CantFail ty body_fn1)
- match_result2
- = returnDs match_result1
+ mk_default fail | exhaustive_case = []
+ | otherwise = [(DEFAULT, [], fail)]
+ un_mentioned_constructors
+ = mkUniqSet data_cons `minusUniqSet` mkUniqSet [ con | (con, _, _) <- match_alts]
+ exhaustive_case = isEmptyUniqSet un_mentioned_constructors
--- The difference in combineGRHSMatchResults is that there is no
--- need to let-bind to avoid code duplication
-combineGRHSMatchResults :: MatchResult -> MatchResult -> DsM MatchResult
-combineGRHSMatchResults (MatchResult CanFail ty1 body_fn1)
- (MatchResult can_it_fail ty2 body_fn2)
- = returnDs (MatchResult can_it_fail ty1 (\ body -> body_fn1 (body_fn2 body)))
-combineGRHSMatchResults match_result1 match_result2
- = -- Delegate to avoid duplication of code
- combineMatchResults match_result1 match_result2
-\end{code}
-
-%************************************************************************
-%* *
-\subsection[dsExprToAtom]{Take an expression and produce an atom}
-%* *
-%************************************************************************
-
-\begin{code}
-dsArgToAtom :: DsCoreArg -- The argument expression
- -> (CoreArg -> DsM CoreExpr) -- Something taking the argument *atom*,
- -- and delivering an expression E
- -> DsM CoreExpr -- Either E or let x=arg-expr in E
-
-dsArgToAtom (TyArg t) continue_with = continue_with (TyArg t)
-dsArgToAtom (LitArg l) continue_with = continue_with (LitArg l)
-dsArgToAtom (VarArg arg) continue_with = dsExprToAtomGivenTy arg (coreExprType arg) continue_with
-
-dsExprToAtomGivenTy
- :: CoreExpr -- The argument expression
- -> Type -- Type of the argument
- -> (CoreArg -> DsM CoreExpr) -- Something taking the argument *atom*,
- -- and delivering an expression E
- -> DsM CoreExpr -- Either E or let x=arg-expr in E
-
-dsExprToAtomGivenTy (Var v) arg_ty continue_with = continue_with (VarArg v)
-dsExprToAtomGivenTy (Lit v) arg_ty continue_with = continue_with (LitArg v)
-dsExprToAtomGivenTy arg_expr arg_ty continue_with
- = newSysLocalDs arg_ty `thenDs` \ arg_id ->
- continue_with (VarArg arg_id) `thenDs` \ body ->
- returnDs (
- if isUnpointedType arg_ty
- then Case arg_expr (PrimAlts [] (BindDefault arg_id body))
- else Let (NonRec arg_id arg_expr) body
- )
-
-dsArgsToAtoms :: [DsCoreArg]
- -> ([CoreArg] -> DsM CoreExpr)
- -> DsM CoreExpr
-
-dsArgsToAtoms [] continue_with = continue_with []
-
-dsArgsToAtoms (arg:args) continue_with
- = dsArgToAtom arg $ \ arg_atom ->
- dsArgsToAtoms args $ \ arg_atoms ->
- continue_with (arg_atom:arg_atoms)
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-type DsCoreArg = GenCoreArg CoreExpr{-NB!-} Unused
-
-mkAppDs :: CoreExpr -> [DsCoreArg] -> DsM CoreExpr
-mkConDs :: Id -> [DsCoreArg] -> DsM CoreExpr
-mkPrimDs :: PrimOp -> [DsCoreArg] -> DsM CoreExpr
-
-mkAppDs fun args
- = dsArgsToAtoms args $ \ atoms ->
- returnDs (mkGenApp fun atoms)
-
-mkConDs con args
- = dsArgsToAtoms args $ \ atoms ->
- returnDs (Con con atoms)
-
-mkPrimDs op args
- = dsArgsToAtoms args $ \ atoms ->
- returnDs (Prim op atoms)
-\end{code}
-
-\begin{code}
-showForErr :: Outputable a => a -> String -- Boring but useful
-showForErr thing = showSDoc (ppr thing)
-
mkErrorAppDs :: Id -- The error function
-> Type -- Type to which it should be applied
-> String -- The error message string to pass
= getSrcLocDs `thenDs` \ src_loc ->
let
full_msg = showSDoc (hcat [ppr src_loc, text "|", text msg])
- msg_lit = NoRepStr (_PK_ full_msg)
in
- returnDs (mkApp (Var err_id) [ty] [LitArg msg_lit])
+ returnDs (mkApps (Var err_id) [Type ty, mkStringLit full_msg])
\end{code}
%************************************************************************
getSrcLocDs `thenDs` \ src_loc ->
let
full_msg = showSDoc (hcat [ppr src_loc, text "|", ppr pat])
- msg_lit = NoRepStr (_PK_ full_msg)
in
mapDs (mk_bind val_var msg_var) binders `thenDs` \ binds ->
returnDs ( (val_var, val_expr) :
- (msg_var, Lit msg_lit) :
+ (msg_var, mkStringLit full_msg) :
binds )
| otherwise
= mkErrorAppDs iRREFUT_PAT_ERROR_ID tuple_ty (showSDoc (ppr pat)) `thenDs` \ error_expr ->
- matchSimply val_expr LetMatch pat tuple_ty local_tuple error_expr `thenDs` \ tuple_expr ->
- newSysLocalDs tuple_ty `thenDs` \ tuple_var ->
+ matchSimply val_expr LetMatch pat local_tuple error_expr `thenDs` \ tuple_expr ->
+ newSysLocalDs tuple_ty `thenDs` \ tuple_var ->
let
- mk_tup_bind binder = (binder, mkTupleSelector binders binder (Var tuple_var))
+ mk_tup_bind binder = (binder, mkTupleSelector binders binder tuple_var (Var tuple_var))
in
returnDs ( (tuple_var, tuple_expr) : map mk_tup_bind binders )
where
-- (mk_bind sv bv) generates
-- bv = case sv of { pat -> bv; other -> error-msg }
-- Remember, pat binds bv
- = matchSimply (Var scrut_var) LetMatch pat binder_ty
+ = matchSimply (Var scrut_var) LetMatch pat
(Var bndr_var) error_expr `thenDs` \ rhs_expr ->
returnDs (bndr_var, rhs_expr)
where
binder_ty = idType bndr_var
- error_expr = mkApp (Var iRREFUT_PAT_ERROR_ID) [binder_ty] [VarArg msg_var]
+ error_expr = mkApps (Var iRREFUT_PAT_ERROR_ID) [Type binder_ty, Var msg_var]
- is_simple_pat (TuplePat ps) = all is_triv_pat ps
- is_simple_pat (ConPat _ _ ps) = all is_triv_pat ps
+ is_simple_pat (TuplePat ps True{-boxed-}) = all is_triv_pat ps
+ is_simple_pat (ConPat _ _ _ _ ps) = all is_triv_pat ps
is_simple_pat (VarPat _) = True
- is_simple_pat (ConOpPat p1 _ p2 _) = is_triv_pat p1 && is_triv_pat p2
- is_simple_pat (RecPat _ _ ps) = and [is_triv_pat p | (_,p,_) <- ps]
+ is_simple_pat (RecPat _ _ _ _ ps) = and [is_triv_pat p | (_,p,_) <- ps]
is_simple_pat other = False
is_triv_pat (VarPat v) = True
\begin{code}
mkTupleExpr :: [Id] -> CoreExpr
-mkTupleExpr [] = Con unitDataCon []
+mkTupleExpr [] = mkConApp unitDataCon []
mkTupleExpr [id] = Var id
-mkTupleExpr ids = mkCon (tupleCon (length ids))
- (map idType ids)
- [ VarArg i | i <- ids ]
+mkTupleExpr ids = mkConApp (tupleCon (length ids))
+ (map (Type . idType) ids ++ [ Var i | i <- ids ])
\end{code}
\begin{code}
mkTupleSelector :: [Id] -- The tuple args
-> Id -- The selected one
+ -> Id -- A variable of the same type as the scrutinee
-> CoreExpr -- Scrutinee
-> CoreExpr
-mkTupleSelector [var] should_be_the_same_var scrut
+mkTupleSelector [var] should_be_the_same_var scrut_var scrut
= ASSERT(var == should_be_the_same_var)
scrut
-mkTupleSelector vars the_var scrut
+mkTupleSelector vars the_var scrut_var scrut
= ASSERT( not (null vars) )
- Case scrut (AlgAlts [(tupleCon (length vars), vars, Var the_var)] NoDefault)
+ Case scrut scrut_var [(DataCon (tupleCon (length vars)), vars, Var the_var)]
\end{code}
Now fail.33 is a function, so it can be let-bound.
\begin{code}
-mkFailurePair :: Type -- Result type of the whole case expression
- -> DsM (CoreExpr -> CoreBinding,
- -- Binds the newly-created fail variable
+mkFailurePair :: CoreExpr -- Result type of the whole case expression
+ -> DsM (CoreBind, -- Binds the newly-created fail variable
-- to either the expression or \ _ -> expression
CoreExpr) -- Either the fail variable, or fail variable
-- applied to unit tuple
-mkFailurePair ty
- | isUnpointedType ty
- = newFailLocalDs (voidTy `mkFunTy` ty) `thenDs` \ fail_fun_var ->
- newSysLocalDs voidTy `thenDs` \ fail_fun_arg ->
- returnDs (\ body ->
- NonRec fail_fun_var (Lam (ValBinder fail_fun_arg) body),
- App (Var fail_fun_var) (VarArg voidId))
+mkFailurePair expr
+ | isUnLiftedType ty
+ = newFailLocalDs (unitTy `mkFunTy` ty) `thenDs` \ fail_fun_var ->
+ newSysLocalDs unitTy `thenDs` \ fail_fun_arg ->
+ returnDs (NonRec fail_fun_var (Lam fail_fun_arg expr),
+ App (Var fail_fun_var) (mkConApp unitDataCon []))
| otherwise
= newFailLocalDs ty `thenDs` \ fail_var ->
- returnDs (\ body -> NonRec fail_var body, Var fail_var)
+ returnDs (NonRec fail_var expr, Var fail_var)
+ where
+ ty = coreExprType expr
\end{code}
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