functionReturn.ts(6,25): error TS2322: Type 'undefined' is not assignable to type 'string'.
functionReturn.ts(9,5): error TS2322: Type 'undefined' is not assignable to type 'string'.
functionReturn.ts(13,5): error TS2322: Type 'undefined' is not assignable to type 'string'.


==== functionReturn.ts (3 errors) ====
    function f0(): void { }
    function f1() {
        var n: any = f0();
    }
    function f2(): any { }
    function f3(): string { return; }
                            ~~~~~~
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
    function f4(): string {
        return '';
        return;
        ~~~~~~
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
    }
    function f5(): string {
        return '';
        return undefined;
        ~~~~~~
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
    }