Proposal: Add Eq instance for Control.Exception.ErrorCall

Simon Marlow marlowsd at
Tue Nov 27 14:57:11 CET 2012

On 27/11/12 10:59, Simon Hengel wrote:
> Hi,
> I propose to add an Eq instance for ErrorCall.  The main motivation is
> to make it more convenient to construct predicates that select specific
> exceptions.
> My current use case is testing for expected exceptions.  In Hspec[1] we
> use predicates for that, e.g.:
>    evaluate (head []) `shouldThrow` (== ErrorCall "Prelude.head: empty list")
> But I think it can be useful in other situations and it is consistent
> with the fact that other common exception types have an Eq instance
> (e.g. ArithException, IOException, ExitCode).
> Discussion period: 3 Weeks

Already did it, a few weeks ago:


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