==== tests/cases/compiler/optionalPropertiesTest.ts (4 errors) ====
    var x: {p1:number; p2?:string; p3?:{():number;};};
    
    interface IFoo
    {
        id: number;
        name?: string;
        print?(): void;
    }
    
    
    var foo: IFoo;
    foo = { id: 1234 };                // Ok
    foo = { id: 1234, name: "test" };  // Ok
    foo = { name: "test" };            // Error, id missing
    ~~~
!!! Type '{ name: string; }' is not assignable to type 'IFoo':
!!!   Property 'id' is missing in type '{ name: string; }'.
    foo = {id: 1234, print:()=>{}}	   // Ok
    
    var s = foo.name || "default";
    if (foo.print !== undefined) foo.print();
    
    interface i1 { M: () => void; };
    interface i2 { M?: () => void; };
    interface i3 { M: number; };
    interface i4 { M?: number; };
    
    var test1: i1 = {};
        ~~~~~
!!! Type '{}' is not assignable to type 'i1':
!!!   Property 'M' is missing in type '{}'.
    var test2: i3 = {};
        ~~~~~
!!! Type '{}' is not assignable to type 'i3':
!!!   Property 'M' is missing in type '{}'.
    var test3: i2 = {};
    var test4: i4 = {};
    var test5: i1 = { M: function () { } };
    var test6: i3 = { M: 5 };
    var test7: i2 = { M: function () { } };
    test7 = {};
    var test8: i4 = { M: 5 }
    test8 = {};
    var test9_1: i2;
    var test9_2: i1;
    test9_1 = test9_2;
    var test10_1: i1;
    var test10_2: i2;
    test10_1 = test10_2;
    ~~~~~~~~
!!! Type 'i2' is not assignable to type 'i1':
!!!   Required property 'M' cannot be reimplemented with optional property in 'i2'.