GenAPI drops ref keyword when generating reference source for System.Memory/4.5.5

[ViktorHofer]

Repro: `./generate.sh --package System.Memory,4.5.5
Observe changes in src/referencePackages/src/system.memory/4.5.5/lib/netstandard2.0/System.Memory.cs

GenAPI drops the ref keyword from structs like ReadOnlySpan<T>.

cc @ericstj

[ericstj]

That's odd - it should treat it as ref - though in this case it looks like the assembly defined IsByRefLikeAttribute internally so that could be causing things to get tripped up.

[ericstj]

Hmm, I see plenty of evidence that this never worked, but I'm at a loss for why not and why we didn't have an existing issue / discussion around it. I see the bug in roslyn that we need to fix to support it, so I'll give that a try and see if I run into any problems or rediscover past issues.

[ericstj]

This was fixed in #38179. We'll be able to remove the workaround that added when we ingest the new roslyn with the fix.

[ViktorHofer]

Source-build might be building against the very latest roslyn. Do we need to adjust the code path for source-build only?

[ViktorHofer]

Actually disregard. For GenAPI, source-build and non source-build both use the very latest roslyn so we shouldn't get into an inconsistent state between build variants.

[ericstj]

I made this work so that it's OK if a newer roslyn meets up before we remove the assert, the assert should only pop during testing.