Using new C# 9.0 language feature causes the performance CI tests to fail

[steveharter]

When trying to use the new C# 9.0 'record' usage in tests the dotnet-runtime-perf leg failed with:
Serialization\ConstructorTests\ConstructorTests.Exceptions.cs(156,37): error CS0518: (NETCORE_ENGINEERING_TELEMETRY=Build) Predefined type 'System.Runtime.CompilerServices.IsExternalInit' is not defined or imported

The test csproj did need to add <LangVersion>preview</LangVersion>, which seemed to work fine execpt for the performance leg:

#38959 (comment)

Tagging subscribers to this area: @safern, @ViktorHofer
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[stephentoub]

cc: @DrewScoggins

[DrewScoggins]

I will take a look at this.

[DrewScoggins]

Is the link to the PR above the one where you are seeing the failure? Because when I look at that all of the CI is green.

EDIT: I see, that was taken out of the PR.

[DrewScoggins]

So I investigated this and what happened was that the AzDO controller somehow got disconnected from tracking the Helix work items. You can see that in the failure on AzDO here, https://dev.azure.com/dnceng/public/_build/results?buildId=721665&view=logs&j=319274cb-4008-5c3f-98b0-4b6b2825e9cf. So I dug into the Kusto logs of Helix and for both of the "failed" jobs all of the workitems completed correctly. So there is no problem here, you can just add back that record type and I doubt it will cause an issue. This failure just seems like a transient issue in AzDO.

[safern]

Yeah, I'm seeing the same behavior as @DrewScoggins. @steveharter if you don't want to block your PR on CI, could you merge and put up another PR to re-enable this and see if we can get a repro or if it was just an unrelated transient issue.

[steveharter]

I'll re-add the record type and ping you two if there's an issue. Thanks

[steveharter]

There is still an issue: #38959 (comment)

[steveharter]

@jaredpar is this issue a duplicate of dotnet/roslyn#45510?