Caught this confusing error today.
I tried to compile a very similar example today, where it told me the return type is void even though I’m trying to use the Func overload, despite clearly having return statements in my lambda. I thought this error was weird because the required return type is Animal, which both Dog and Cat are. I’m returning objects in the lambda, so it’s obviously a Func. However, both R# and the compiler can’t figure out that Dog and Cat are Animals and chooses the Action overload and yells at me for trying to return.
ReSharper’s quick-fix context menu also has no idea how to solve the issue. The issue is resolved by casting any of the return statements to Animal. The compiler isn’t confused at all if there is only one return statement (with no cast).