, let tc_name = tyConName tc
, Just tc' <- [lookupNameEnv (vect_tycons env) tc_name]]
-newtype VM a = VM { runVM :: Builtins -> VEnv -> DsM (VEnv, a) }
+data VResult a = Yes VEnv a | No
+
+newtype VM a = VM { runVM :: Builtins -> VEnv -> DsM (VResult a) }
instance Monad VM where
- return x = VM $ \bi env -> return (env, x)
+ return x = VM $ \bi env -> return (Yes env x)
VM p >>= f = VM $ \bi env -> do
- (env', x) <- p bi env
- runVM (f x) bi env'
+ r <- p bi env
+ case r of
+ Yes env' x -> runVM (f x) bi env'
+ No -> return No
+
+noV :: VM a
+noV = VM $ \bi env -> return No
+
+tryV :: VM a -> VM (Maybe a)
+tryV (VM p) = VM $ \bi env -> do
+ r <- p bi env
+ case r of
+ Yes env' x -> return (Yes env' (Just x))
+ No -> return (Yes env Nothing)
liftDs :: DsM a -> VM a
-liftDs p = VM $ \bi env -> do { x <- p; return (env, x) }
+liftDs p = VM $ \bi env -> do { x <- p; return (Yes env x) }
builtin :: (Builtins -> a) -> VM a
-builtin f = VM $ \bi env -> return (env, f bi)
+builtin f = VM $ \bi env -> return (Yes env (f bi))
readEnv :: (VEnv -> a) -> VM a
-readEnv f = VM $ \bi env -> return (env, f env)
+readEnv f = VM $ \bi env -> return (Yes env (f env))
setEnv :: VEnv -> VM ()
-setEnv env = VM $ \_ _ -> return (env, ())
+setEnv env = VM $ \_ _ -> return (Yes env ())
updEnv :: (VEnv -> VEnv) -> VM ()
-updEnv f = VM $ \_ env -> return (f env, ())
+updEnv f = VM $ \_ env -> return (Yes (f env) ())
newTyVar :: FastString -> Kind -> VM Var
newTyVar fs k
= do
builtins <- initBuiltins
env <- initVEnv info
- (env', guts') <- runVM (vectModule guts) builtins env
- return $ updVectInfo env' guts'
+ r <- runVM (vectModule guts) builtins env
+ case r of
+ Yes env' guts' -> return $ updVectInfo env' guts'
+ No -> return guts
vectModule :: ModGuts -> VM ModGuts
vectModule guts = return guts