Function secret_reads_of 

pub fn secret_reads_of<'a>(
    handlers: impl Iterator<Item = &'a Handler>,
    flattened: &HashMap<String, String>,
) -> (SecretReads, Vec<CompileError>)

The literal bynk.Secrets names this context’s handlers read, and whether that list is everything.

Split so callers can scope it differently without the rule differing: bynk-emit’s manifest wants a context’s whole handler set (its names span every file), while this warning wants one file’s handlers at a time, because a diagnostic sink attributes a diagnostic to a path and a merged handler set has thrown that away.