Function rendered_identifier 

pub fn rendered_identifier(spelling: &str) -> bool

The one alphabet every spelling this home renders as a Rust identifier is admitted by, published from the nucleus every road here already reads it through. Whether one spelling is a single Rust identifier a rendering is willing to write.

ASCII only, and _ alone is refused because it is the wildcard pattern rather than a name. ONE alphabet, seated with the token home, for every spelling any home renders in identifier position — a path segment, an exported address, a stamped item’s own name, a declared grammar’s word. A second copy would agree with this one until one of them was edited, and the failure would surface in a consumer’s build with no idea where the name came from; the homes that once each carried a copy now all read this seat.