function function throwError(propName: string): voidthrowError(propName: stringpropName: string) {
    throw new var Error: ErrorConstructor
new (message?: string | undefined, options?: ErrorOptions | undefined) => Error (+1 overload)Error(`'${propName: stringpropName}' is required`)
}

function function doSomething(someArg?: void): voiddoSomething(someArg: voidsomeArg = function throwError(propName: string): voidthrowError("someArg")) {
    return someArg: voidsomeArg;
}

function doSomething(someArg?: void): voiddoSomething();
// Uncaught Error: someArg is required