//// [subtypingWithObjectMembers2.ts] interface Base { foo: string; } interface Derived extends Base { bar: string; } // N and M have the same name, same accessibility, same optionality, and N is a subtype of M // foo properties are valid, bar properties cause errors in the derived class declarations module NotOptional { interface A { foo: Base; bar: Base; } interface B extends A { foo: Derived; // ok bar: string; // error } interface A2 { 1: Base; 2.0: Base; } interface B2 extends A2 { 1: Derived; // ok 2: string; // error } interface A3 { '1': Base; '2.0': Base; } interface B3 extends A3 { '1': Derived; // ok '2.0': string; // error } } // same cases as above but with optional module Optional { interface A { foo?: Base; bar?: Base; } interface B extends A { foo?: Derived; // ok bar?: string; // error } interface A2 { 1?: Base; 2.0?: Base; } interface B2 extends A2 { 1?: Derived; // ok 2?: string; // error } interface A3 { '1'?: Base; '2.0'?: Base; } interface B3 extends A3 { '1'?: Derived; // ok '2.0'?: string; // error } } //// [subtypingWithObjectMembers2.js]