[main] Update dependencies from dotnet/linker

[dotnet-maestro]

This pull request updates the following dependencies

From https://github.com/dotnet/linker

• Subscription: 0d6d6ae4-f71f-4395-53e6-08d8e409d87d
• Build: 20210928.1
• Date Produced: September 29, 2021 12:25:58 AM UTC
• Commit: d31e26ef3e552f1795c86a88c1451d36922e08f1
• Branch: refs/heads/main

• Updates:
  • Microsoft.NET.ILLink.Tasks: from 7.0.100-1.21460.1 to 7.0.100-1.21478.1

[marek-safar]

The failures look like possible regression from dotnet/linker#2288

@vitek-karas @MichalStrehovsky PTAL

[vitek-karas]

I'm looking into this.
It's definitely caused by the binder flags changes in the linker. I'll gather all of the different cases this hits and then try to determine the best solution. Since this it integration into "main" (7.0), I think it's OK to keep this PR opened for a bit until we resolve those issues.

[vitek-karas]

There are 3 types of issues here, in all cases linker warns in places it didn't before:

1. Using BindingFlags.GetField in a call to Type.GetField - using this binding flag has no effect at runtime, but the new linker treats this as "unknown binding flags" which leads to marking all fields (and the caller doesn't have annotation matching that request).
2. Activator.CreateInstance used with the binding flag BindingFlags.CreateInstance - this actually might have a runtime effect (I'm not 100% sure). It should probably not be warning in the linker for this case?
3. Linker failed to warn in cases where calls to reflection methods with binding flags coming from method parameters. This exposes actually new places in the runtime which need annotations. Linker SHOULD warn in these cases. This only affects OOB assemblies which we didn't make trim-ready, so it's just about updating suppressions.

[MichalStrehovsky]

Thanks for investigating @vitek-karas!

Looks like the 1 and 2 would be fixed if we went with what was in the first commit of dotnet/linker#2288 - only consider null and don't care about extra flags we don't understand.

But it looks like that would just silently stomp over the pre-existing issue that is: the BindingFlagsAreUnsupported logic is too conservative. E.g. for typeof(SomeType).GetField("FooBar", .Public | .Instance | .GetField) we would go and mark all fields on FooBar. That behavior existed before #2288; now we just aligned with it.

I'm looking into making BindingFlagsAreUnsupported more precise. This should fix 1 and 2.

[MichalStrehovsky]

Thanks for the suppressions Vitek!