runghc -fdefer-type-errors

[Edward Z. Yang]

Excerpts from Simon Peyton-Jones's message of Mon Mar 11 16:04:31 -0700 2013:
> Aha.  It is indeed true that
> 
>     ghc -fdefer-type-errors -w
> 
> does not suppress the warnings that arise from the type errors; indeed there is no current way to do so.  How to do that?
> 
> To be kosher there should really be a flag to switch off those warnings alone, perhaps
>     -fno-warn-type-errors
> 
> So then -fwarn-type-errors is on by default, but is only relevant when -fdefer-type-errors is on.  Once -fdefer-type-errors is on, -fno-warn-type-errors and -fwarn-type-errors suppress or enable the warnings.  -w would then include -fno-warn-type-errors.
> 
> Is that a design everyone would like?  If so, woudl someone like to open a ticket, implement it, update the documentation, and send a patch?

SGTM.

Edward