pub a: @typeOf(@This()),
b : make_type(),

const Self = @This();

fn ret_b(comptime self: *const type) type {
    var foo = @ptrCast(*const Self, self);
    return foo.b;
}

fn make_type() type {
    const self = @This();
    const std = @import("std");

    const x = std.mem.eql(u8, ret_b(&self).ret_b(), "main");

    std.debug.assert(x);

    return bool;
}

test "" {
    const std = @import("std");
    const s = @This(){ .a = std };
    s.x;
}