[Haskell-cafe] Bug in HTTP (bad internal error handling)

Claus Reinke claus.reinke at talk21.com
Sat Oct 16 04:29:46 EDT 2010

> After it catches this error, the function returns (line 376):
> return (fail (show e))
> The "fail" is running in the Either monad (The Result type = Either).
> This calls the default Monad implementation of fail, which is just a
> call to plain old error. This basically causes the entire program to
> crash.

> Actually, it appears that simpleHTTP isn't actually supposed to throw
> an IOException, and it is instead supposed to return a ConnError
> result. So the real fix is to fix the code to make this happen. But

Sounds like a victim of 


For mtl clients, 'fail' for 'Either' used to call 'Left'. That was
changed, though the ticket does not indicate the library
versions affected.


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