Request: suppress specific warnings at specific places

[Simon Marlow]

> GHC's excellent warnings are very helpful.  They would be somewhat
> more so if it were possible to suppress a warning about a specific bit
> of code.  One possible syntax (to which I gave no commitment) would be
>=20
>   {-# WOFF "non-exhaustive pattern matches" #-}
>   <offending code>
>   {-# WON "non-exhaustive pattern matches" #-}
>=20
> .  Another would be
>=20
>   {-# WOFF 523 #-}
>   <offending code>
>   {-# WON 523 #-}
>=20
> where 523 is a warning number emitted with the warning message.
>=20
> This would be particularly useful with the recently granted wish for
> -Werror.

This would be nice, but it would be tricky to implement: declarations
have to be tagged with a list of "exceptions" to the prevailing warning
settings.  I doubt we'll do this any time soon, but patches are welcome
as usual...

(of course, the workaround is to put the offending code into a module of
its own, and use OPTIONS to turn off the appropriate warnings).

Cheers,
	SImon