runReaderT has the wrong type

[ndmitchell]

Taking the mtl library, using the --hoogle flag, I generates:

newtype ReaderT r (m :: * -> *) a :: * -> (* -> *) -> * -> *
[ReaderT] :: (r -> m a) -> ReaderT r a
[runReaderT] :: ReaderT r a -> r -> m a
runReaderT :: ReaderT r m a -> r -> m a

Observe that the first runReaderT (the one in brackets) is missing the m field from the ReaderT type. Originally reported at https://code.google.com/p/ndmitchell/issues/detail?id=557

[RyanGlScott]

I'm not sure what fixed this, but this doesn't appear to be the case anymore. I'll add a regression test.

[ndmitchell]

What does the [runReaderT] mean - specifically the square brackets? Why does it occur twice in the reexport?

[RyanGlScott]

Square brackets means that an entity is not exported directly, but rather indirectly through a catch-all export like ReaderT(..). In the test case I added, I export both ReaderT(..) and runReaderT to ensure that both variants would show the correct type signature.

It would be good to actually document this—I'm about to file an issue regarding this.

[RyanGlScott]

See #807.