We need to make this off-by-default - in the MSBuild parts by suppressing the warning by default for now.
@sbomer - any idea exactly how to go about it (so that it's possible to "unsuppress" it somehow).

@tlakollo could you please take a look?

We need to make this off-by-default - in the MSBuild parts by suppressing the warning by default for now.
@sbomer - any idea exactly how to go about it (so that it's possible to "unsuppress" it somehow).

Ideally it would be suppressed the same as any other warnings with NoWarn under SuppressTrimAnalysisWarnings - but I assume the idea is that it should be separate from the other trim warnings until we are able to prune these down to only ones that are truly redundant? In that case, maybe we could give the new warnings a new warning version - 8 would make them show up only for .net 8. Or if we want these to forever be opt-in because we lack confidence that we can make them not noisy, then I would just add a new command-line flag that you would set from MSBuild with <_ExtraTrimmerArgs>--enable-redundant-suppression-detection</_ExtraTrimmerArgs> or similar.

I guess the command line option is the simplest... I really hoped we would be able to do this purely through warning system, but the warning level feels weird (we don't use it for anything... not sure we should start).

Another option that avoids a command-line argument would be to introduce a separate MSBuild flag that controls whether NoWarn includes the new warning code(s). Something like:

<PropertyGroup Condition="'$(_TrimmerShowRedundantSuppressions)' != 'true'">
    <NoWarn>$(NoWarn);IL2121</NoWarn>
</PropertyGroup>

But if we are planning for this to be turned on by default in the future I would lean towards using warning waves.