There's a pattern that arises fairly often: catching every exception thrown by code. The naive approach is to do something like:

result <- try someCode

case result of

Left (e :: SomeException) -> putStrLn $ "It failed: " ++ show e

Right realValue -> useRealValue

This seems perfectly valid, except that it catches a number of exceptions which seemingly should not be caught. In particular, it catches the async exceptions used by both killThread and timeout.

I think it's fair to say that there's not going to be a single function that solves all cases correctly, but it is a common enough situation that people need to write code that resumes work in the case of an exception that I think we need to either have some guidelines for the right approach here, or perhaps even a utility function along the lines of:

shouldBeCaught :: SomeException -> Bool

One first stab at such a function would be to return `False` for AsyncException and Timeout, and `True` for everything else, but I'm not convinced that this is sufficient. Are there any thoughts on the right approach to take here?