Diagnostics from Source Generators do not respect suppression

[chsienki]

Diagnostics produced by source generators do not respect the /warnAsError or /noWarn compiler flags.

[geeknoid]

A couple more related points:

• "#pragma warning dissable" has no impact on warnings produced by a source generator, the warnings are always presented to the user.

• On the flip side, source generator warnings don't seem to be visible to the VS IDE. The same "#pragma warning disable" statement which has no effect on disabling a source generator warning ends up being underlined by VS and flagged as a superfluous suppression. So the IDE isn't treating the warning from the source generator has being present, so it thinks the suppression is for naught.