Macro __global 

macro_rules! __global {
    () => { ... };
    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr; $($rest:tt)*) => { ... };
    (Effect::$method:ident($init:expr); $($rest:tt)*) => { ... };
}

Can be used to create a GlobalSignal, a global Calculated or a global Effect.