type of stToIO

[Simon Peyton-Jones]

Ross

| The library documentation says
| 
| 	stToIO :: ST s a -> IO a
| 
| but PrelIOBase says
| 
| 	stToIO :: ST RealWorld a -> IO a
| 
| The documented type would be unsafe (as it is in Classic Hugs), so it
| seems necessary to mention the real world in the documentation.

I discussed this with John Launchbury who pointed out a much
better type for stToIO

	stToIO :: (forall s. ST s a) -> IO a

That avoids exposing RealWorld while preserving soundness.  Better, eh?

I'm going to implement this in hslibs/ and document the reason in the
library documentation.

Simon