This implements the first strategy proposed by Botond to filter unresolved overload sets: by arity. We don't have easy access to the CallExpr from OverloadExpr, CXXDependentScopeMemberExpr or DependentScopeDeclRefExpr, so we add tracking for that in TraverseCallExpr. This was previously reviewed upstream on GitHub: https://github.com/mozsearch/mozsearch/pull/851 Differential Revision: https://phabricator.services.mozilla.com/D231584