Macro accesses 

macro_rules! accesses {
    {
    $( $([ $prefix:ident ])? $kind:ident, $description:tt; )*
} => { ... };
}

Generate the extension trait and its impl

Input is the set of “kinds of thing”, each of which corresponds to an ErrorKind.

Input syntax

    thing, "DESCRIPTION";           // Provide thing_error_kind(), using ThingAccessFailed
    [Prefix] THING, "DESCRIPTION";  // uses PrefixThingAccessFAiled