fn resolve_associated_trait_item<'a>(
    ty: Ty<'a>,
    module: DefId,
    item_name: Symbol,
    ns: Namespace,
    cx: &mut DocContext<'a>,
) -> Vec<AssocItem>Expand description
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.