Interactive "do" notation in GHCi
Enable GHCi to run commands under StateT monad based on IO or maybe even any other monad based on IO. So that you could for example exec a state and "fall" into this monad.
This could be generalized by supporting interactive "do" notation. Currently doing something like:
(flip execStateT) state $ do
raises "Empty 'do' construct" warning, but GHCi could go into interactive mode where it would be possible to write one command after another and it would execute them.