Function rustc_query_system::query::job::connected_to_root

fn connected_to_root(
    query_map: &QueryMap,
    query: QueryJobId,
    visited: &mut FxHashSet<QueryJobId>,
) -> bool

Finds out if there’s a path to the compiler root (aka. code which isn’t in a query) from query without going through any of the queries in visited. This is achieved with a depth first search.