{"ast_node_type":"other","tokens":[{"end":49,"kind":"keyword","start":0,"text":"if"}]}
        if caller.is_1zst() || callee.is_1zst() {
        // 1-ZST are compatible with all 1-ZST (and with nothing else).
            return interp_ok(caller.is_1zst() && callee.is_1zst());