Function find_references 

pub fn find_references(
    word: &str,
    all_docs: &[(Url, Arc<ParsedDoc>)],
    include_declaration: bool,
    kind: Option<SymbolKind>,
) -> Vec<Location>

Find all locations where word is referenced across the given documents. If include_declaration is true, also includes the declaration site. Pass kind to restrict results to a particular symbol category; None falls back to the original word-based walker (better some results than none).