+%
+% (c) The AQUA Project, Glasgow University, 1998
+%
+\section[TcForeign]{Typechecking \tr{foreign} declarations}
+
+A foreign declaration is used to either give an externally
+implemented function a Haskell type (and calling interface) or
+give a Haskell function an external calling interface. Either way,
+the range of argument and result types these functions can accommodate
+is restricted to what the outside world understands (read C), and this
+module checks to see if a foreign declaration has got a legal type.
+
+\begin{code}
+module TcForeign
+ (
+ tcForeignImports
+ , tcForeignExports
+ ) where
+
+#include "HsVersions.h"
+
+import HsSyn ( HsDecl(..), ForeignDecl(..), HsExpr(..),
+ ExtName(..), isDynamic, MonoBinds(..),
+ OutPat(..)
+ )
+import RnHsSyn ( RenamedHsDecl, RenamedForeignDecl )
+
+import TcMonad
+import TcEnv ( tcLookupClassByKey, newLocalId, tcLookupGlobalValue )
+import TcType ( tcInstTcType, tcInstSigType, tcSplitRhoTy, zonkTcTypeToType )
+import TcMonoType ( tcHsType )
+import TcHsSyn ( TcMonoBinds, maybeBoxedPrimType, TypecheckedForeignDecl, TcIdOcc(..),
+ TcForeignExportDecl )
+import TcExpr ( tcId, tcPolyExpr )
+import Inst ( emptyLIE, LIE, plusLIE )
+import CoreSyn
+
+import ErrUtils ( Message )
+import Id ( Id, idName )
+import Name ( nameOccName )
+import MkId ( mkUserId )
+import Type ( isUnpointedType
+ , splitFunTys
+ , splitTyConApp_maybe
+ , splitForAllTys
+ , splitRhoTy
+ , isForAllTy
+ , mkForAllTys
+ )
+import TyVar ( emptyTyVarEnv )
+
+
+import TysWiredIn ( isFFIArgumentTy, isFFIResultTy,
+ isFFIExternalTy, isAddrTy
+ )
+import Type ( Type )
+import Unique
+import Unify ( unifyTauTy )
+import Outputable
+import Util
+import CmdLineOpts ( opt_GlasgowExts )
+import Maybes ( maybeToBool )
+
+\end{code}
+
+\begin{code}
+tcForeignImports :: [RenamedHsDecl] -> TcM s ([Id], [TypecheckedForeignDecl])
+tcForeignImports decls =
+ mapAndUnzipTc tcFImport [ foreign_decl | ForD foreign_decl <- decls, isForeignImport foreign_decl]
+
+tcForeignExports :: [RenamedHsDecl] -> TcM s (LIE s, TcMonoBinds s, [TcForeignExportDecl s])
+tcForeignExports decls =
+ foldlTc combine (emptyLIE, EmptyMonoBinds, [])
+ [ foreign_decl | ForD foreign_decl <- decls, isForeignExport foreign_decl]
+ where
+ combine (lie, binds, fs) fe =
+ tcFExport fe `thenTc ` \ (a_lie, b, f) ->
+ returnTc (lie `plusLIE` a_lie, b `AndMonoBinds` binds, f:fs)
+
+-- defines a binding
+isForeignImport :: ForeignDecl name -> Bool
+isForeignImport (ForeignDecl _ (Just _) _ _ _ _) = True
+isForeignImport (ForeignDecl _ Nothing _ Dynamic _ _) = True
+isForeignImport _ = False
+
+-- exports a binding
+isForeignExport :: ForeignDecl name -> Bool
+isForeignExport (ForeignDecl _ Nothing _ ext_nm _ _) = not (isDynamic ext_nm)
+isForeignExport _ = False
+
+\end{code}
+
+\begin{code}
+tcFImport :: RenamedForeignDecl -> TcM s (Id, TypecheckedForeignDecl)
+tcFImport fo@(ForeignDecl nm Nothing hs_ty Dynamic cconv src_loc) =
+ tcAddSrcLoc src_loc $
+ tcAddErrCtxt (foreignDeclCtxt fo) $
+ tcHsType hs_ty `thenTc` \ sig_ty ->
+ let
+ -- drop the foralls before inspecting the structure
+ -- of the foreign type.
+ (_, t_ty) = splitForAllTys sig_ty
+ in
+ case splitFunTys t_ty of
+ (arg_tys, res_ty) ->
+ checkForeignExport True t_ty arg_tys res_ty `thenTc_`
+ let i = (mkUserId nm sig_ty) in
+ returnTc (i, (ForeignDecl i Nothing undefined Dynamic cconv src_loc))
+
+tcFImport fo@(ForeignDecl nm imp_exp hs_ty ext_nm cconv src_loc) =
+ tcAddSrcLoc src_loc $
+ tcAddErrCtxt (foreignDeclCtxt fo) $
+
+ tcHsType hs_ty `thenTc` \ ty ->
+ -- Check that the type has the right shape
+ -- and that the argument and result types are acceptable.
+ let
+ -- drop the foralls before inspecting the structure
+ -- of the foreign type.
+ (_, t_ty) = splitForAllTys ty
+ in
+ case splitFunTys t_ty of
+ (arg_tys, res_ty) ->
+ checkForeignImport (isDynamic ext_nm) ty arg_tys res_ty `thenTc_`
+ let i = (mkUserId nm ty) in
+ returnTc (i, (ForeignDecl i imp_exp undefined ext_nm cconv src_loc))
+
+tcFExport :: RenamedForeignDecl -> TcM s (LIE s, TcMonoBinds s, TcForeignExportDecl s)
+tcFExport fo@(ForeignDecl nm imp_exp hs_ty ext_nm cconv src_loc) =
+ tcAddSrcLoc src_loc $
+ tcAddErrCtxt (foreignDeclCtxt fo) $
+
+ tcHsType hs_ty `thenTc` \ sig_ty ->
+ tcInstSigType sig_ty `thenNF_Tc` \ sig_tc_ty ->
+ tcPolyExpr (HsVar nm) sig_tc_ty `thenTc` \ (rhs, lie, _, _, _) ->
+
+ let
+ -- drop the foralls before inspecting the structure
+ -- of the foreign type.
+ (_, t_ty) = splitForAllTys sig_ty
+ in
+ case splitFunTys t_ty of
+ (arg_tys, res_ty) ->
+ checkForeignExport False t_ty arg_tys res_ty `thenTc_`
+ -- we're exporting a function, but at a type possibly more constrained
+ -- than its declared/inferred type. Hence the need
+ -- to create a local binding which will call the exported function
+ -- at a particular type (and, maybe, overloading).
+ newLocalId (nameOccName nm) sig_tc_ty `thenNF_Tc` \ i ->
+ let
+ i2 = TcId i
+ bind = VarMonoBind i2 rhs
+ in
+ returnTc (lie, bind, ForeignDecl i2 imp_exp undefined ext_nm cconv src_loc)
+ -- ^^^^^^^^^
+ -- ToDo: fill the type field in with something sensible.
+
+\end{code}
+
+
+\begin{code}
+checkForeignImport :: Bool -> Type -> [Type] -> Type -> TcM s ()
+checkForeignImport is_dynamic ty args res
+ | is_dynamic =
+ -- * first arg has got to be an Addr
+ case args of
+ [] -> check False (illegalForeignTyErr True{-Arg-} ty)
+ (x:xs) ->
+ check (isAddrTy x) (illegalForeignTyErr True{-Arg-} ty) `thenTc_`
+ mapTc (checkForeignArg isFFIArgumentTy) xs `thenTc_`
+ checkForeignRes (isFFIResultTy) res
+ | otherwise =
+ mapTc (checkForeignArg isFFIArgumentTy) args `thenTc_`
+ checkForeignRes (isFFIResultTy) res
+
+checkForeignExport :: Bool -> Type -> [Type] -> Type -> TcM s ()
+checkForeignExport is_dynamic ty args res
+ | is_dynamic =
+ -- * the first (and only!) arg has got to be a function type
+ -- * result type is an Addr
+ case args of
+ [arg] ->
+ case splitFunTys arg of
+ (arg_tys, res_ty) ->
+ mapTc (checkForeignArg isFFIExternalTy) arg_tys `thenTc_`
+ checkForeignRes (isFFIResultTy) res_ty `thenTc_`
+ checkForeignRes (isAddrTy) res
+ _ -> check False (illegalForeignTyErr True{-Arg-} ty)
+ | otherwise =
+ mapTc (checkForeignArg isFFIExternalTy) args `thenTc_`
+ checkForeignRes (isFFIResultTy) res
+
+check :: Bool -> Message -> TcM s ()
+check True _ = returnTc ()
+check _ the_err = addErrTc the_err `thenNF_Tc_` returnTc ()
+
+checkForeignArg :: (Type -> Bool) -> Type -> TcM s ()
+checkForeignArg pred ty = check (pred ty) (illegalForeignTyErr True{-Arg-} ty)
+
+-- Check that the type has the form
+-- (IO t) and that t satisfies the given predicate.
+--
+checkForeignRes :: (Type -> Bool) -> Type -> TcM s ()
+checkForeignRes pred_res_ty ty =
+ case (splitTyConApp_maybe ty) of
+ Just (io, [res_ty])
+ | (uniqueOf io) == ioTyConKey &&
+ pred_res_ty res_ty
+ -> returnTc ()
+ _ -> check False (illegalForeignTyErr False{-Res-} ty)
+
+\end{code}
+
+Warnings
+
+\begin{code}
+illegalForeignTyErr isArg ty
+ = hang (hsep [ptext SLIT("Unacceptable"), arg_or_res, ptext SLIT("type in foreign declaration")])
+ 4 (hsep [ ptext SLIT("type:"), ppr ty])
+ where
+ arg_or_res
+ | isArg = ptext SLIT("argument")
+ | otherwise = ptext SLIT("result")
+
+foreignDeclCtxt fo =
+ hang (ptext SLIT("When checking a foreign declaration:"))
+ 4 (ppr fo)
+
+\end{code}