Function reject_unknown_keys 

pub fn reject_unknown_keys<V: Source>(
    object: Fields<'_, V>,
    declared: &[String],
    path: &str,
) -> Result<(), ProbeError>

Refuse a key that names nothing the type declares.

An error and not a warning: a misspelled member name would otherwise silently test the default value, and the two emitters that skipped it produced a sample the third one refused.

Errors

ProbeError::Unknown, naming the offending key’s path.