This is the only way to do this today. The early pitches for declaration macros had "code item" macros that could do this, and there's a partial implementation of the feature in the compiler behind an experimental feature flag (CodeItemMacros), but nobody has followed through with pitch/proposal/complete implementation. Personally, I haven't seen that many use cases for code-item macros vs. the other kinds, so I haven't looked into them further.
Doug