Microsoft took the hit and revamped the runtime when generics landed. I'm sure they would take another hit if such a critical feature presented itself and there

Microsoft took the hit and revamped the runtime when generics landed. I'm sure they would take another hit if such a critical feature presented itself and there wasn't a good way to retrofit it. The only two warts that strike me off-hand are covariant arrays and System.Nullable being value-type only. Overall Microsoft has done a great job of building on earlier decisions. Including functions as first-class types (System.Delegate) in V1 is probably the biggest and was a deliberate break with Java's approach. It has enabled a ton of features: lambdas, LINQ, Expression, etc. The fact that LINQ can be turned into an AST with Expression<T> means you can also construct code dynamically at a much higher level than IL.Emit() while delegates mean you can get the JIT to provide the equivalent of a function pointer to the native code.