src/s-reader.js
function expectRE($, regexp) {
    let str = acceptRE($, regexp);
    if (str === null) {
        throw Tools.syntaxError("Unexpected character", $.pos);
    }
    return str;
}
function expectRE($, regexp) {
    let str = acceptRE($, regexp);
    if (str === null) {
        throw Tools.syntaxError("Unexpected character", $.pos);
    }
    return str;
}
(object, object) => string