#endif
import HsSyn
-import TcHsSyn
-- NB: The desugarer, which straddles the source and Core worlds, sometimes
-- needs to see source types
import Id
import Var
import VarSet
-import PrelInfo
import DataCon
import TysWiredIn
import BasicTypes
dsExpr (HsIPVar ip) = return (Var (ipNameName ip))
dsExpr (HsLit lit) = dsLit lit
dsExpr (HsOverLit lit) = dsOverLit lit
-dsExpr (HsWrap co_fn e) = do { co_fn' <- dsHsWrapper co_fn
- ; e' <- dsExpr e
- ; return (co_fn' e') }
+
+dsExpr (HsWrap co_fn e)
+ = do { co_fn' <- dsHsWrapper co_fn
+ ; e' <- dsExpr e
+ ; warn_id <- doptDs Opt_WarnIdentities
+ ; when warn_id $ warnAboutIdentities e' co_fn'
+ ; return (co_fn' e') }
dsExpr (NegApp expr neg_expr)
= App <$> dsExpr neg_expr <*> dsLExpr expr
-- We need the `ListComp' form to use `deListComp' (rather than the "do" form)
-- because the interpretation of `stmts' depends on what sort of thing it is.
--
-dsExpr (HsDo ListComp stmts body result_ty)
- = -- Special case for list comprehensions
- dsListComp stmts body elt_ty
- where
- [elt_ty] = tcTyConAppArgs result_ty
-
-dsExpr (HsDo DoExpr stmts body result_ty)
- = dsDo stmts body result_ty
-
-dsExpr (HsDo GhciStmt stmts body result_ty)
- = dsDo stmts body result_ty
-
-dsExpr (HsDo ctxt@(MDoExpr tbl) stmts body result_ty)
- = do { (meth_binds, tbl') <- dsSyntaxTable tbl
- ; core_expr <- dsMDo ctxt tbl' stmts body result_ty
- ; return (mkLets meth_binds core_expr) }
-
-dsExpr (HsDo PArrComp stmts body result_ty)
- = -- Special case for array comprehensions
- dsPArrComp (map unLoc stmts) body elt_ty
- where
- [elt_ty] = tcTyConAppArgs result_ty
-
-dsExpr (HsIf guard_expr then_expr else_expr)
- = mkIfThenElse <$> dsLExpr guard_expr <*> dsLExpr then_expr <*> dsLExpr else_expr
+dsExpr (HsDo ListComp stmts res_ty) = dsListComp stmts res_ty
+dsExpr (HsDo PArrComp stmts _) = dsPArrComp (map unLoc stmts)
+dsExpr (HsDo DoExpr stmts _) = dsDo stmts
+dsExpr (HsDo GhciStmt stmts _) = dsDo stmts
+dsExpr (HsDo MDoExpr stmts _) = dsDo stmts
+dsExpr (HsDo MonadComp stmts _) = dsMonadComp stmts
+
+dsExpr (HsIf mb_fun guard_expr then_expr else_expr)
+ = do { pred <- dsLExpr guard_expr
+ ; b1 <- dsLExpr then_expr
+ ; b2 <- dsLExpr else_expr
+ ; case mb_fun of
+ Just fun -> do { core_fun <- dsExpr fun
+ ; return (mkCoreApps core_fun [pred,b1,b2]) }
+ Nothing -> return $ mkIfThenElse pred b1 b2 }
\end{code}
-- singletonP x1 +:+ ... +:+ singletonP xn
--
dsExpr (ExplicitPArr ty []) = do
- emptyP <- dsLookupGlobalId emptyPName
+ emptyP <- dsLookupDPHId emptyPName
return (Var emptyP `App` Type ty)
dsExpr (ExplicitPArr ty xs) = do
- singletonP <- dsLookupGlobalId singletonPName
- appP <- dsLookupGlobalId appPName
+ singletonP <- dsLookupDPHId singletonPName
+ appP <- dsLookupDPHId appPName
xs' <- mapM dsLExpr xs
return . foldr1 (binary appP) $ map (unary singletonP) xs'
where
Haskell 98 report:
\begin{code}
-dsDo :: [LStmt Id]
- -> LHsExpr Id
- -> Type -- Type of the whole expression
- -> DsM CoreExpr
-
-dsDo stmts body result_ty
+dsDo :: [LStmt Id] -> DsM CoreExpr
+dsDo stmts
= goL stmts
where
- -- result_ty must be of the form (m b)
- (m_ty, _b_ty) = tcSplitAppTy result_ty
-
- goL [] = dsLExpr body
- goL ((L loc stmt):lstmts) = putSrcSpanDs loc (go loc stmt lstmts)
+ goL [] = panic "dsDo"
+ goL (L loc stmt:lstmts) = putSrcSpanDs loc (go loc stmt lstmts)
- go _ (ExprStmt rhs then_expr _) stmts
+ go _ (LastStmt body _) stmts
+ = ASSERT( null stmts ) dsLExpr body
+ -- The 'return' op isn't used for 'do' expressions
+
+ go _ (ExprStmt rhs then_expr _ _) stmts
= do { rhs2 <- dsLExpr rhs
- ; case tcSplitAppTy_maybe (exprType rhs2) of
- Just (container_ty, returning_ty) -> warnDiscardedDoBindings rhs container_ty returning_ty
- _ -> return ()
+ ; warnDiscardedDoBindings rhs (exprType rhs2)
; then_expr2 <- dsExpr then_expr
; rest <- goL stmts
; return (mkApps then_expr2 [rhs2, rest]) }
go loc (RecStmt { recS_stmts = rec_stmts, recS_later_ids = later_ids
, recS_rec_ids = rec_ids, recS_ret_fn = return_op
, recS_mfix_fn = mfix_op, recS_bind_fn = bind_op
- , recS_rec_rets = rec_rets, recS_dicts = _ev_binds }) stmts
+ , recS_rec_rets = rec_rets, recS_ret_ty = body_ty }) stmts
= ASSERT( length rec_ids > 0 )
- ASSERT( isEmptyTcEvBinds _ev_binds ) -- No method binds
goL (new_bind_stmt : stmts)
where
- -- returnE <- dsExpr return_id
- -- mfixE <- dsExpr mfix_id
- new_bind_stmt = L loc $ BindStmt (mkLHsPatTup later_pats) mfix_app
- bind_op
- noSyntaxExpr -- Tuple cannot fail
+ new_bind_stmt = L loc $ BindStmt (mkLHsPatTup later_pats)
+ mfix_app bind_op
+ noSyntaxExpr -- Tuple cannot fail
tup_ids = rec_ids ++ filterOut (`elem` rec_ids) later_ids
+ tup_ty = mkBoxedTupleTy (map idType tup_ids) -- Deals with singleton case
rec_tup_pats = map nlVarPat tup_ids
later_pats = rec_tup_pats
rets = map noLoc rec_rets
-
- mfix_app = nlHsApp (noLoc mfix_op) mfix_arg
- mfix_arg = noLoc $ HsLam (MatchGroup [mkSimpleMatch [mfix_pat] body]
- (mkFunTy tup_ty body_ty))
- mfix_pat = noLoc $ LazyPat $ mkLHsPatTup rec_tup_pats
- body = noLoc $ HsDo DoExpr rec_stmts return_app body_ty
- return_app = nlHsApp (noLoc return_op) (mkLHsTupleExpr rets)
- body_ty = mkAppTy m_ty tup_ty
- tup_ty = mkBoxedTupleTy (map idType tup_ids) -- Deals with singleton case
-
+ mfix_app = nlHsApp (noLoc mfix_op) mfix_arg
+ mfix_arg = noLoc $ HsLam (MatchGroup [mkSimpleMatch [mfix_pat] body]
+ (mkFunTy tup_ty body_ty))
+ mfix_pat = noLoc $ LazyPat $ mkLHsPatTup rec_tup_pats
+ body = noLoc $ HsDo DoExpr (rec_stmts ++ [ret_stmt]) body_ty
+ ret_app = nlHsApp (noLoc return_op) (mkLHsTupleExpr rets)
+ ret_stmt = noLoc $ mkLastStmt ret_app
+ -- This LastStmt will be desugared with dsDo,
+ -- which ignores the return_op in the LastStmt,
+ -- so we must apply the return_op explicitly
+
+handle_failure :: LPat Id -> MatchResult -> SyntaxExpr Id -> DsM CoreExpr
-- 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")
+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 :: Located e -> String
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 :: HsStmtContext Name
- -> [(Name,Id)]
- -> [LStmt Id]
- -> LHsExpr Id
- -> Type -- Type of the whole expression
- -> DsM CoreExpr
-
-dsMDo ctxt tbl stmts body result_ty
- = goL stmts
- where
- goL [] = dsLExpr body
- goL ((L loc stmt):lstmts) = putSrcSpanDs loc (go loc stmt lstmts)
-
- (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
- go _ (LetStmt binds) stmts
- = do { rest <- goL stmts
- ; dsLocalBinds binds rest }
+%************************************************************************
+%* *
+ Warning about identities
+%* *
+%************************************************************************
- go _ (ExprStmt rhs _ rhs_ty) stmts
- = do { rhs2 <- dsLExpr rhs
- ; warnDiscardedDoBindings rhs m_ty rhs_ty
- ; rest <- goL stmts
- ; return (mkApps (Var then_id) [Type rhs_ty, Type b_ty, rhs2, rest]) }
-
- go _ (BindStmt pat rhs _ _) stmts
- = do { body <- goL 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
- ; return (mkApps (Var bind_id) [Type (hsLPatType pat), Type b_ty,
- rhs', Lam var match_code]) }
-
- go loc (RecStmt { recS_stmts = rec_stmts, recS_later_ids = later_ids
- , recS_rec_ids = rec_ids, recS_rec_rets = rec_rets
- , recS_dicts = _ev_binds }) stmts
- = ASSERT( length rec_ids > 0 )
- ASSERT( length rec_ids == length rec_rets )
- ASSERT( isEmptyTcEvBinds _ev_binds )
- pprTrace "dsMDo" (ppr later_ids) $
- goL (new_bind_stmt : stmts)
- where
- new_bind_stmt = L loc $ mkBindStmt (mk_tup_pat later_pats) mfix_app
-
- -- 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 (nlHsTyApp 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 = mkBoxedTupleTy (map idType (later_ids' ++ rec_ids)) -- Deals with singleton case
-
- return_app = nlHsApp (nlHsTyApp return_id [tup_ty])
- (mkLHsTupleExpr 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
+Warn about functions that convert between one type and another
+when the to- and from- types are the same. Then it's probably
+(albeit not definitely) the identity
+\begin{code}
+warnAboutIdentities :: CoreExpr -> (CoreExpr -> CoreExpr) -> DsM ()
+warnAboutIdentities (Var v) co_fn
+ | idName v `elem` conversionNames
+ , let fun_ty = exprType (co_fn (Var v))
+ , Just (arg_ty, res_ty) <- splitFunTy_maybe fun_ty
+ , arg_ty `tcEqType` res_ty -- So we are converting ty -> ty
+ = warnDs (vcat [ ptext (sLit "Call of") <+> ppr v <+> dcolon <+> ppr fun_ty
+ , nest 2 $ ptext (sLit "can probably be omitted")
+ , parens (ptext (sLit "Use -fno-warn-identities to suppress this messsage)"))
+ ])
+warnAboutIdentities _ _ = return ()
+
+conversionNames :: [Name]
+conversionNames
+ = [ toIntegerName, toRationalName
+ , fromIntegralName, realToFracName ]
+ -- We can't easily add fromIntegerName, fromRationalName,
+ -- becuase they are generated by literals
\end{code}
-
%************************************************************************
%* *
\subsection{Errors and contexts}
\begin{code}
-- Warn about certain types of values discarded in monadic bindings (#3263)
-warnDiscardedDoBindings :: LHsExpr Id -> Type -> Type -> DsM ()
-warnDiscardedDoBindings rhs container_ty returning_ty = do {
- -- Warn about discarding non-() things in 'monadic' binding
- ; warn_unused <- doptDs Opt_WarnUnusedDoBind
- ; if warn_unused && not (returning_ty `tcEqType` unitTy)
- then warnDs (unusedMonadBind rhs returning_ty)
- else do {
- -- Warn about discarding m a things in 'monadic' binding of the same type,
- -- but only if we didn't already warn due to Opt_WarnUnusedDoBind
- ; warn_wrong <- doptDs Opt_WarnWrongDoBind
- ; case tcSplitAppTy_maybe returning_ty of
- Just (returning_container_ty, _) -> when (warn_wrong && container_ty `tcEqType` returning_container_ty) $
- warnDs (wrongMonadBind rhs returning_ty)
- _ -> return () } }
+warnDiscardedDoBindings :: LHsExpr Id -> Type -> DsM ()
+warnDiscardedDoBindings rhs rhs_ty
+ | Just (m_ty, elt_ty) <- tcSplitAppTy_maybe rhs_ty
+ = do { -- Warn about discarding non-() things in 'monadic' binding
+ ; warn_unused <- doptDs Opt_WarnUnusedDoBind
+ ; if warn_unused && not (isUnitTy elt_ty)
+ then warnDs (unusedMonadBind rhs elt_ty)
+ else
+ -- Warn about discarding m a things in 'monadic' binding of the same type,
+ -- but only if we didn't already warn due to Opt_WarnUnusedDoBind
+ do { warn_wrong <- doptDs Opt_WarnWrongDoBind
+ ; case tcSplitAppTy_maybe elt_ty of
+ Just (elt_m_ty, _) | warn_wrong, m_ty `tcEqType` elt_m_ty
+ -> warnDs (wrongMonadBind rhs elt_ty)
+ _ -> return () } }
+
+ | otherwise -- RHS does have type of form (m ty), which is wierd
+ = return () -- but at lesat this warning is irrelevant
unusedMonadBind :: LHsExpr Id -> Type -> SDoc
-unusedMonadBind rhs returning_ty
- = ptext (sLit "A do-notation statement discarded a result of type") <+> ppr returning_ty <> dot $$
+unusedMonadBind rhs elt_ty
+ = ptext (sLit "A do-notation statement discarded a result of type") <+> ppr elt_ty <> dot $$
ptext (sLit "Suppress this warning by saying \"_ <- ") <> ppr rhs <> ptext (sLit "\",") $$
ptext (sLit "or by using the flag -fno-warn-unused-do-bind")
wrongMonadBind :: LHsExpr Id -> Type -> SDoc
-wrongMonadBind rhs returning_ty
- = ptext (sLit "A do-notation statement discarded a result of type") <+> ppr returning_ty <> dot $$
+wrongMonadBind rhs elt_ty
+ = ptext (sLit "A do-notation statement discarded a result of type") <+> ppr elt_ty <> dot $$
ptext (sLit "Suppress this warning by saying \"_ <- ") <> ppr rhs <> ptext (sLit "\",") $$
ptext (sLit "or by using the flag -fno-warn-wrong-do-bind")
\end{code}
projects / ghc-hetmet.git / blobdiff