[Haskell-cafe] Where is the documentation on exception types kept?

Simon Hengel sol at typeful.net
Wed Nov 7 21:53:29 CET 2012


> I am trying to catch an "thread blocked on MVar indefinitely exception."  Of
> course I can use ::SomeException as explained in http://hackage.haskell.org/
> packages/archive/base/latest/doc/html/Control-Exception.html#g:3 but there 
> is no explanation as to how to find the more case specific exceptions.  
> http://hackage.haskell.org/packages/archive/base/latest/doc/html/Control-
> Concurrent-MVar.html#t:MVar does not discuss exceptions at all!  Indeed, I 
> don't know of any haddock pages that include descriptions of exception types
> :( :O

In this particular case it's easy:


But in general, figuring out the exception type is not straight forward.
Personally, I think an uncaught exception should print the type of that
exception (e.g. use a derived show instance).  But most of them have a
show instance that is useful for end-users.

The upcoming 1.4.0 release of Hspec will print the type of uncaught
exceptions in test cases.  So if you are into BDD/TDD that might be


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