What about an identifier that is an mixin

[André Puel via Digitalmars-d]

One thing that I miss sometimes when doing meta programming is 
being able to hide that a function should be called with mixin.

For example (pardon my lack of creativity):
    // Instead of
    string declare_a() {
        return "int a;"
    }

    int func() {
        mixin(declare_a);
        return a;
    }

    // Could we have?
    mixin declare_a() {
        return "int a;";
    }

    int func() {
        declare_a;
        return a;
    }

I think this could be useful when one is creating Idiom and 
Patterns, you could hide implementations details.