Function rustdoc::passes::collect_intra_doc_links::resolve_associated_trait_item

fn resolve_associated_trait_item(
    did: DefId, 
    module: DefId, 
    item_name: Symbol, 
    ns: Namespace, 
    cx: &mut DocContext<'_>
) -> Option<(AssocKind, DefId)>

Look to see if a resolved item has an associated item named item_name.

Given [std::io::Error::source], where source is unresolved, this would find std::error::Error::source and return <io::Error as error::Error>::source.