arraySigChecking.ts(11,17): error TS1268: An index signature parameter type must be 'string', 'number', 'symbol', or a template literal type.
arraySigChecking.ts(18,27): error TS2322: Type 'void' is not assignable to type 'string'.
arraySigChecking.ts(22,13): error TS2322: Type 'number' is not assignable to type 'number[]'.
arraySigChecking.ts(22,16): error TS2322: Type 'number' is not assignable to type 'number[]'.


==== arraySigChecking.ts (4 errors) ====
    declare namespace M {
        interface iBar { t: any; }
        interface iFoo extends iBar {
            s: any;
        }
    
        class cFoo {
            t: any;
        }
    
        var foo: { [index: any]; }; // expect an error here
                    ~~~~~
!!! error TS1268: An index signature parameter type must be 'string', 'number', 'symbol', or a template literal type.
    }
    
    interface myInt {
        voidFn(): void;
    }
    declare var myVar: myInt;
    var strArray: string[] = [myVar.voidFn()];
                              ~~~~~~~~~~~~~~
!!! error TS2322: Type 'void' is not assignable to type 'string'.
    
    
    var myArray: number[][][];
    myArray = [[1, 2]];
                ~
!!! error TS2322: Type 'number' is not assignable to type 'number[]'.
                   ~
!!! error TS2322: Type 'number' is not assignable to type 'number[]'.
    
    function isEmpty(l: { length: number }) {
        return l.length === 0;
    }
    
    isEmpty([]);
    isEmpty(new Array(3));
    isEmpty(new Array<string>(3));
    isEmpty(['a']);
    