tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithInheritedPrivates3.ts(9,11): error TS2320: Interface 'A' cannot simultaneously extend types 'C' and 'C2'. Named property 'x' of types 'C' and 'C2' are not identical. tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithInheritedPrivates3.ts(31,15): error TS2320: Interface 'A' cannot simultaneously extend types 'C' and 'C2'. Named property 'x' of types 'C' and 'C2' are not identical. ==== tests/cases/conformance/interfaces/declarationMerging/mergedInterfacesWithInheritedPrivates3.ts (2 errors) ==== class C { private x: number; } class C2 { private x: number; } interface A extends C { // error ~ !!! error TS2320: Interface 'A' cannot simultaneously extend types 'C' and 'C2'. !!! error TS2320: Named property 'x' of types 'C' and 'C2' are not identical. y: string; } interface A extends C2 { z: string; } class D extends C implements A { // error y: string; z: string; } module M { class C { private x: string; } class C2 { private x: number; } interface A extends C { // error, privates conflict ~ !!! error TS2320: Interface 'A' cannot simultaneously extend types 'C' and 'C2'. !!! error TS2320: Named property 'x' of types 'C' and 'C2' are not identical. y: string; } interface A extends C2 { z: string; } }