pub fn find_def_cycle(krate: CrateNum, start: &str) -> Option<Vec<String>>Expand description
Return a cycle path (e.g. ["A", "B", "A"]) if expanding start can reach
itself again through def-to-def references, None otherwise.
Only edges that resolve to another registered def are followed; calls to
primitives (Allocated, Align, …) terminate the walk. The crate’s own
defs are overlaid on the builtin namespace.