Function exposure_is_source_nameable 

pub fn exposure_is_source_nameable(exposure: BuiltinExposure) -> bool

Whether Harn source may write this builtin’s bare name in a call.

A harness method is reached as harness.<capability>.<method> rather than as a global, so it is not bare-nameable either. Undeclared is a migration state rather than a promise, and answering true there keeps this predicate from inventing a restriction the contract has not made yet.