AMP (#8004) almost finished, review would be nice

[Edward Z. Yang]

Have not looked at patch.

Excerpts from David Luposchainsky's message of Sun Sep 01 12:23:06 -0700 2013:
> 1. Validation does not work due to the warnings issued. Since "sh
> validate" uses -Werror, an AMP warning will stop the compilation before
> tests can even be run. Unfortunately, the build system seems to use the
> variables 'GhcStage1HcOpts' in the build process of phase 1, which is of
> course done with the current (7.6.3 or whatever is installed) compiler.
> When adding "-fno-warn-amp" to that variable phase 1 won't build because
> the parameter is unknown to the old compiler. Is there some sort of
> -"ignore next parameter if unknown" hack, or is there a smart solution?

Well, can you just fix all of the errors?  Otherwise, do an OPTIONS_GHC
block on top of the offending module further bracketed by the appropriate
preprocessor macro.

> 2. Temporarily removing the -Werror constraint from validate-settings.mk
> (or by using custom-settings.mk) makes the validation build go through.
> However, the testsuite defines a couple of violating modules, therefore
> there is unexpected STDERR output, hence a handful of tests fail. Should
> a fix for this be included in the AMP patch, or be done as a separate
> instance?

They should either ignore the warnings or get rid of the error. I think
it makes sense to include it in this process.

> 3. Similarly, GHC defines around 50 offending modules, creating warnings
> in the standard build process. Again, should this be included, or can we
> push that to after the feature freeze and regard it as bugfixing?

(See above)  If you define some of the missing instances you may break
some orphan instances, but if it's just in GHC this should not be a big
deal.

Edward