[mattnewport]

This comment wasn't about gradual typing, it was about power / generality of generics / metaprogramming support. C# fails at this in more ways than lacking value parameters and having limitations on value types.

There is no efficient and syntactically pleasant way to work with numeric types generically for example (I can't write 'a + b' and have it work for any types that provide operator+). That doesn't require C++ compile time duck typing (you could mandate something like C++ Concepts to specify a numeric interface, I believe this is sort of what Haskell typeclasses do) but it's easy, efficient and syntactically pleasant to do in C++.

The limitations of C# generics bite it in other ways too - the members of Enumerable are useful and the syntax is ok (not as nice as F# or C++ Ranges) but C# can't match the performance of C++ Ranges given the way they are implemented. They also get bitten by the operator problem - look at how Enumerable.Sum() has implementations for every built in numeric type and doesn't out of the box support your custom Numeric type.

[Rusky]

Fair enough, typeclasses/traits were what I had in mind here. You're right that C# doesn't have a common interface to constrain your generics with for operator+/etc.