Proxy fail to create for create substitute that returns a derived class from abstract that satisfies interface implicitly about core HOT 5 CLOSED

Yup, verified that the problem is solved by updating Castle.Core version. Thanks @stakx !

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I don't know how any of this works, but there is also the possibility that whatever was not configured correctly, I also made an issue on NSub's repo:
nsubstitute/NSubstitute#730

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This issue seems to be about C# 9 covariant return types, which DynamicProxy should support since version 5.1.0. (See #619.)

Can you please check which version of NSubstitute (and Castle.Core) you are using? Also, which version of .NET are you running your code on?

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Ah...It would seem that the latest NSubstitute release is using Castle.Core version 5.0.0.* according to the csproj.

I am also using .NET 6.0 Windows.

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OK, in that case there's not much to be done on DynamicProxy's side. NSubstitute should probably upgrade their Castle.Core dependency... I've seen in the linked issue that they've already done so.

I'm going to close this issue as it'll likely be resolved after the upgrade. If not, let us know again here and we'll reopen.

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