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Backport of #108328 to release/9.0-staging
/cc @MichalStrehovsky
Customer Impact
One more IDynamicInterfaceCastable related issue. This one was found as we were unblocking tests as part of fixing a customer reported issue (that was known and had known disabled tests). The tests happened to also hit this problem.
The issue is that a cast of a IDynamicInterfaceCastable object to a variant interface would store the wrong value into CastCache - we'd answer the first cast correctly, but a second time the same pair of type is checked for castability, we'd use the wrong cached value and invalid cast exception would happen.
Regression
Regressed in .NET 8, likely in #90234.
Testing
Added targeted test that is part of this PR. We also subsequently enabled more testing in #108376 but that depends on both PRs so it's in a separate PR.
Risk
This should be low risk, it only affects IDynamicInterfaceCastable and we made sure the caching logic is same as CoreCLR. This has been in main for 2 months.
IMPORTANT: If this backport is for a servicing release, please verify that:
The PR target branch is
release/X.0-staging, notrelease/X.0.If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.