interface default implementation mixin

[JS]

I'm trying to create a default interface mixin tempate. Some 
prototype code I've come up with generates the members property 
but I get an error I don't understand:

http://dpaste.dzfl.pl/58c0392d
void myfunc(float a, int b, string c) { a.myfunc(a, b, c); }

/d650/f247.d(70): Error: no property 'myfunc' for type 'float'


The mixin doesn't seem to work properly though even though it is 
generating a valid implementation of the interface... unless I'm 
missing something.