Macro aversion::assign_message_ids

assign_message_ids!() { /* proc-macro */ }

Implement MessageId for a bunch of types at once.

The assign_message_ids! macro uses the following syntax:

assign_message_ids! {
    Foo: 100,
    Bar: 101,
    Baz: 109,
}

This is equivalent to writing the following MessageId implementations by hand:

impl MessageId for Foo {
   const MSG_ID: u16 = 100;
}
impl MessageId for Bar {
   const MSG_ID: u16 = 101;
}
impl MessageId for Baz {
   const MSG_ID: u16 = 109;
}