Function literals can't be class members

[JS]

trying to use a lambda inside a sub template gives an error.

mixin template a
{
    template b()
    {
       enum b = { }();
    }
    mixin(b!());
}

gives the error in the subject, removing the nesting or using a 
function instead of a lamda produces no error, yet all are 
essentially semantically equivalent... just the lamda version 
requires less typing. (in fact, it would be nice to have a 
simplification of template b() = { ... }();)