Can you give examples of the latter? I know from personal experience (of looking at disassembly of JIT output) that, when CLR generics are instantiated with structs, it is perfectly capable of full monomorphization with inlining of stuff similar to C++ <algorithm>.
Yes, structs are generally very good because they are mostly monomorphized. I haven't tested lately if structs of the same size but different types will fully monomorphize or if they share code and so require a small dispatch table. There was a CLR release awhile back where they discussed sharing code in this way to reduce code bloat.
There are still a few pitfalls. Off the top of my head, accessing generic static fields, ie. static class Foo<T> { public readonly static T Member }. Mainly for non-struct members, this typically requires a hashtable-like lookup to resolve the offset for the.
Also, generic interface dispatch can't be monomorphized, ie. interface IFoo<T> { void Method<T>(T value); }, so this too costs more than a regular virtual call because it too requires a hashtable-like lookup to resolve the generic overload to invoke.
