{"ast_node_type":"function","tokens":[{"end":100,"kind":"keyword","start":0,"text":"fn"}]}
    fn visit_infer(&mut self, _inf_id: HirId, inf_span: Span, kind: InferKind<'v>) -> Self::Result {
impl<'v> Visitor<'v> for HirPlaceholderCollector {
        self.spans.push(inf_span);