tests/cases/conformance/interfaces/interfaceDeclarations/interfaceWithPropertyThatIsPrivateInBaseType.ts(5,11): error TS2430: Interface 'Foo' incorrectly extends interface 'Base'. Property 'x' is private in type 'Base' but not in type 'Foo'. tests/cases/conformance/interfaces/interfaceDeclarations/interfaceWithPropertyThatIsPrivateInBaseType.ts(13,11): error TS2430: Interface 'Foo2' incorrectly extends interface 'Base2'. Property 'x' is private in type 'Base2' but not in type 'Foo2'. ==== tests/cases/conformance/interfaces/interfaceDeclarations/interfaceWithPropertyThatIsPrivateInBaseType.ts (2 errors) ==== class Base { private x: number; } interface Foo extends Base { // error ~~~ !!! error TS2430: Interface 'Foo' incorrectly extends interface 'Base'. !!! error TS2430: Property 'x' is private in type 'Base' but not in type 'Foo'. x: number; } class Base2 { private x: T; } interface Foo2 extends Base2 { // error ~~~~ !!! error TS2430: Interface 'Foo2' incorrectly extends interface 'Base2'. !!! error TS2430: Property 'x' is private in type 'Base2' but not in type 'Foo2'. x: number; }