Improve monad transformers support #198
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This PR fixes the following limitations:
SeldaT, ie.SeldaT b (StateT s IO)did not have aMonadState sinstance,SeldaTcould only be used as outermost element in the transformer stack, ie.StateT s (SeldaT b IO)did not have aMonadSeldainstance,onExceptionmade it unsafe to use a base monad that uses any form of short-circuiting that is not an exception, ie. ExceptT.Fixing that last point requires using
generalBracketintroduced inexceptions-0.9, so I had to bump the dependency requirement. I am not sure how this impacts the range of GHC versions that can be supported.Supporting
ExceptT/MonadErroris rather important for applications based on servant.