var a: boolean | number | string;
if (typeof a !== 'boolean') {
    // a is narrowed to "number | string"
    for (var i = 0; i < 1; i++) {
        for (var j = 0; j < 1; j++) {}
        if (typeof a === 'string') {
            // a is narrowed to "string'
            for (var j = 0; j < 1; j++) {
                a.length; // Error: Property 'length' does not exist on type 'never'.
            }
        }
    }
}