{"ast_node_type":"function","tokens":[{"end":73,"kind":"keyword","start":0,"text":"pub"}]}
    pub fn const_fn_def(&self) -> Option<(DefId, GenericArgsRef<'tcx>)> {
    /// find as the `func` in a [`TerminatorKind::Call`].
        let const_ty = self.constant()?.const_.ty();