{"ast_node_type":"function","tokens":[{"end":62,"kind":"keyword","start":0,"text":"fn"}]}
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
impl<Cx: PatCx> fmt::Debug for WitnessPat<Cx> {
        self.ctor().fmt_fields(f, self.ty(), self.fields.iter())