=== tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithObjectMembersOptionality.ts ===
// Derived member is not optional but base member is, should be ok

interface Base { foo: string; }
>Base : Base
>foo : string

interface Derived extends Base { bar: string; }
>Derived : Derived
>Base : Base
>bar : string

interface Derived2 extends Derived { baz: string; }
>Derived2 : Derived2
>Derived : Derived
>baz : string

// S is a subtype of a type T, and T is a supertype of S, if one of the following is true, where S' denotes the apparent type (section 3.8.1) of S:
//   - S' and T are object types and, for each member M in T, one of the following is true:
//      - M is a property and S' contains a property N where
//          M and N have the same name,
//          the type of N is a subtype of that of M,
//          M and N are both public or both private, and
//          if M is a required property, N is also a required property.
//      - M is an optional property and S' contains no property of the same name as M.
interface T {
>T : T

    Foo?: Base;
>Foo : Base
>Base : Base
}

interface S extends T {
>S : S
>T : T

    Foo: Derived
>Foo : Derived
>Derived : Derived
}

interface T2 {
>T2 : T2

    1?: Base; 
>Base : Base
}

interface S2 extends T2 {
>S2 : S2
>T2 : T2

    1: Derived;
>Derived : Derived
}

interface T3 {
>T3 : T3

    '1'?: Base;
>Base : Base
}

interface S3 extends T3 {
>S3 : S3
>T3 : T3

    '1.': Derived;
>Derived : Derived
}

// object literal case
var a: { Foo?: Base; };
>a : { Foo?: Base; }
>Foo : Base
>Base : Base

var b = { Foo: <Derived>null };
>b : { Foo: Derived; }
>{ Foo: <Derived>null } : { Foo: Derived; }
>Foo : Derived
><Derived>null : Derived
>Derived : Derived
>null : null

var r = true ? a : b;
>r : { Foo?: Base; }
>true ? a : b : { Foo?: Base; }
>true : boolean
>a : { Foo?: Base; }
>b : { Foo: Derived; }

module TwoLevels {
>TwoLevels : typeof TwoLevels

    interface T {
>T : T

        Foo?: Base;
>Foo : Base
>Base : Base
    }

    interface S extends T {
>S : S
>T : T

        Foo: Derived2 
>Foo : Derived2
>Derived2 : Derived2
    }

    interface T2 {
>T2 : T2

        1?: Base;
>Base : Base
    }

    interface S2 extends T2 {
>S2 : S2
>T2 : T2

        1: Derived2;
>Derived2 : Derived2
    }

    interface T3 {
>T3 : T3

        '1'?: Base;
>Base : Base
    }

    interface S3 extends T3 {
>S3 : S3
>T3 : T3

        '1.': Derived2;
>Derived2 : Derived2
    }

    // object literal case
    var a: { Foo?: Base; };
>a : { Foo?: Base; }
>Foo : Base
>Base : Base

    var b = { Foo: <Derived2>null };
>b : { Foo: Derived2; }
>{ Foo: <Derived2>null } : { Foo: Derived2; }
>Foo : Derived2
><Derived2>null : Derived2
>Derived2 : Derived2
>null : null

    var r = true ? a : b;
>r : { Foo?: Base; }
>true ? a : b : { Foo?: Base; }
>true : boolean
>a : { Foo?: Base; }
>b : { Foo: Derived2; }
}