+\begin{code}
+legalIncomingTyCon :: TyCon -> Bool
+-- It's illegal to return foreign objects and (mutable)
+-- bytearrays from a _ccall_ / foreign declaration
+-- (or be passed them as arguments in foreign exported functions).
+legalIncomingTyCon tc
+ | getUnique tc `elem` [ foreignObjTyConKey, byteArrayTyConKey,
+ mutableByteArrayTyConKey ]
+ = False
+ -- It's also illegal to make foreign exports that take unboxed
+ -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
+ | otherwise
+ = boxedMarshalableTyCon tc
+
+legalOutgoingTyCon :: DynFlags -> Bool -> TyCon -> Bool
+-- Checks validity of types going from Haskell -> external world
+-- The boolean is true for a 'safe' call (when we don't want to
+-- pass Haskell pointers to the world)
+legalOutgoingTyCon dflags be_safe tc
+ | be_safe && getUnique tc `elem` [byteArrayTyConKey, mutableByteArrayTyConKey]
+ = False
+ | otherwise
+ = marshalableTyCon dflags tc
+
+marshalableTyCon dflags tc
+ = (dopt_GlasgowExts dflags && isUnLiftedTyCon tc)
+ || boxedMarshalableTyCon tc
+
+boxedMarshalableTyCon tc
+ = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey, int32TyConKey, int64TyConKey
+ , wordTyConKey, word8TyConKey, word16TyConKey, word32TyConKey, word64TyConKey
+ , floatTyConKey, doubleTyConKey
+ , addrTyConKey, charTyConKey, foreignObjTyConKey
+ , stablePtrTyConKey
+ , byteArrayTyConKey, mutableByteArrayTyConKey
+ , boolTyConKey
+ ]