dynamic classes and duck typing

[bearophile]

Walter Bright:
> and then s.foo(3), if foo is not a compile time member of s, is 
> rewritten as:
>     s.opDynamic!("foo")(3);

I don't understand, isn't this the right translation?
s.opDynamic("foo", 3);
If the "foo" name is known at compile time only (as in all C# examples and in Python) you can't use a template argument.
(And then it becomes useful to have associative arrays that are fast when the number of keys is small, < 10).

Bye,
bearophile