class C {
        i: number | number[];

        constructor() {
            this.i = 0;
        }

        foo(): void {
            this.i = [];
        }

        bar(): number {
            if (typeof this.i === 'number') {
                this.foo();
                return this.i;
            }
            return 0;
        }
    }

    console.log(typeof new C().bar());