{"ast_node_type":"other","tokens":[{"end":67,"kind":"keyword","start":0,"text":"///"}]}
///   invocation. We are assuming we already know there is a match.
/// - `interp` is a map of meta-variables to the tokens (non-terminals) they matched in the
/// - `src` is the RHS of the MBE, that is, the "example" we are filling in.