fn cycle_check(
query_map: &QueryMap,
query: QueryJobId,
span: Span,
stack: &mut Vec<(Span, QueryJobId)>,
visited: &mut FxHashSet<QueryJobId>,
) -> Option<Option<(QueryJobId, usize)>>Expand description
Look for query cycles by doing a depth first search starting at query.
span is the reason for the query to execute. This is initially DUMMY_SP.
If a cycle is detected, this initial value is replaced with the span causing
the cycle.