Macro nested_struct

macro_rules! nested_struct {
    (
        $(#[$meta:meta])*
        $vis:vis struct $name:ident {
            $(
                $(#[$field_meta:meta])*
                $(@nested(#[$field_nested_meta:meta]))*
                $field_vis:vis $field_name:ident : $field_ty:ident $({
                    $($field_ty_inner:tt)*
                })?
            ),*
        $(,)? }
    ) => { ... };
    (@nested $(#[$meta:meta])* $vis:vis $name:ident {$($fields:tt)*}) => { ... };
    (@nested $(#[$meta:meta])* $vis:vis $name:ident) => { ... };
}