Exception instance for SomeAsyncException should define displayException

[alt-romes]

The instance for SomeAsyncException is currently is currently defined as

-- | @since base-4.7.0.0
instance Exception SomeAsyncException

with an empty implementation.
This means that if the wrapped exception has a custom displayException definition, that definition is lost.Given that the Show instance simply omits the SomeAsyncException wrapper, perhaps a reasonable definition would be:

instance Exception SomeAsyncException where
  displayException (SomeExceptionException e) = displayException e

We propose to update the instance Exception SomeAsyncException to the snippet above.

Originally by @edsko on the GHC issue tracker.

[parsonsmatt]

Yes please! Great catch

[alt-romes]

Perhaps this can be moved along? @Bodigrim what do you think?

[Bodigrim]

Yes, seems uncontroversial to me: we unpack e in instance Exception SomeException, we should do the same for SomeAsyncException.

Dear CLC members, as an exception, given that the proposed change is very simple, holidays are looming and I trust @alt-romes to create a GHC MR promptly, let's vote on it without waiting for MR.

@tomjaguarpaw @parsonsmatt @angerman @hasufell @velveteer @mixphix

+1 from me.

[alt-romes]

I had forgotten about preparing an MR, but promptly made one now

https://gitlab.haskell.org/ghc/ghc/-/merge_requests/13725

Thanks @Bodigrim

[hasufell]

+1

[tomjaguarpaw]

+1

[parsonsmatt]

+1

[Bodigrim]

Thanks all, that's enough votes to approve.