Feedback on applying implicit exceptions wanted

[Andreas Klebinger]

I'm currently working out ideas for potential optimizations in pattern 
matching compilation for GHC.

While I think the theory works out fine in regards to exceptions I would 
like feedback on the possible implications.

Trac ticket with details is here:
https://ghc.haskell.org/trac/ghc/ticket/14201#comment:4

As for the theory I worked based of the assumptions that error = bottom 
and pattern match failure = error. Otherwise we get different results 
from both cases even in theory.

While I mostly worry about the practical implications I would also 
appreciate any other feedback.