in packages/runtime/runtime.js [134:143]
exports.mark = function(genFun) {
if (Object.setPrototypeOf) {
Object.setPrototypeOf(genFun, GeneratorFunctionPrototype);
} else {
genFun.__proto__ = GeneratorFunctionPrototype;
define(genFun, toStringTagSymbol, "GeneratorFunction");
}
genFun.prototype = Object.create(Gp);
return genFun;
};