Macro __get_set_decl 

macro_rules! __get_set_decl {
    (
        $class: ident,
        $field_name: ident,
        $( $js_field_name: literal )?,
        @get( $( $get_arg: ident: $get_arg_type: ty ),* ) -> $get_ty: ty
            $get_body: block,
    ) => { ... };
    (
        $class: ident,
        $field_name: ident,
        $( $js_field_name: literal )?,
        @set( $( $set_arg: ident: $set_arg_type: ty ),* )
            $( -> $field_prop_set_ty: ty )?
            $set_body: block
    ) => { ... };
    (
        $class: ident,
        $field_name: ident,
        $( $js_field_name: literal )?,
        @get( $( $get_arg: ident: $get_arg_type: ty ),* ) -> $get_ty: ty
            $get_body: block,
        @set( $( $set_arg: ident: $set_arg_type: ty ),* )
            $( -> $field_prop_set_ty: ty )?
            $set_body: block
    ) => { ... };
    (
        $class: ident,
        $field_name: ident,
        $( $js_field_name: literal )?,
    ) => { ... };
}

Internal macro to declare a getter/setter name.