basicTypes/Var.lhs:194: Non-exhaustive patterns in function readMutTyVar

[Jeffrey R. Lewis]

Simon Peyton-Jones wrote:

> Thanks.  I've added both tests to the HEAD.
> Jeff: let us know the outcome re bug-hunt.

Attached is a much shorter demonstration of the first bug.  I don't have the HEAD checked out anywhere right now, so it isn't convenient to change it myself.

--Jeff

P.S.  the second bug isn't really a bug (in the sense that we need to hunt for it!) - the extension of functional dependencies over derived instances isn't implemeneted yet!
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module Bug where

primDup :: Int -> IO Int
primDup = undefined

dup () = call primDup

class Call    c h | c -> h where
    call  :: c -> h

instance Call c h => Call (Int->c) (Int->h) where call f = call . f