implict type cast in generic method

Question

why do I get a compiler error in the following code stating: Cannot implicty convert type SpecialNode to T even though T must derive from NodeBase as I defined

Answer 1

The problem is that the function may be called with a type parameter T, which derives from NodeBase but not from SpecialNode. The compiler doesn't check the semantics of the if statement, so it doesn't know, that T has to be a specialNode.

You would need to use an explicit cast to T in order to satisfy your compiler.