tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer2.ts(11,11): error TS2430: Interface 'B' incorrectly extends interface 'A'. Index signatures are incompatible. Type 'Base' is not assignable to type 'Derived'. Property 'bar' is missing in type 'Base'. tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer2.ts(24,27): error TS2344: Type 'Base' does not satisfy the constraint 'Derived'. tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer2.ts(32,15): error TS2430: Interface 'B3' incorrectly extends interface 'A'. Index signatures are incompatible. Type 'Base' is not assignable to type 'T'. tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer2.ts(36,15): error TS2430: Interface 'B4' incorrectly extends interface 'A'. Index signatures are incompatible. Type 'Derived' is not assignable to type 'T'. tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer2.ts(40,15): error TS2430: Interface 'B5' incorrectly extends interface 'A'. Index signatures are incompatible. Type 'Derived2' is not assignable to type 'T'. ==== tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithNumericIndexer2.ts (5 errors) ==== // Derived type indexer must be subtype of base type indexer interface Base { foo: string; } interface Derived extends Base { bar: string; } interface Derived2 extends Derived { baz: string; } interface A { [x: number]: Derived; } interface B extends A { ~ !!! error TS2430: Interface 'B' incorrectly extends interface 'A'. !!! error TS2430: Index signatures are incompatible. !!! error TS2430: Type 'Base' is not assignable to type 'Derived'. !!! error TS2430: Property 'bar' is missing in type 'Base'. [x: number]: Base; // error } interface B2 extends A { [x: number]: Derived2; // ok } module Generics { interface A { [x: number]: T; } interface B extends A { ~~~~ !!! error TS2344: Type 'Base' does not satisfy the constraint 'Derived'. [x: number]: Derived; // error } interface B2 extends A { [x: number]: Derived2; // ok } interface B3 extends A { ~~ !!! error TS2430: Interface 'B3' incorrectly extends interface 'A'. !!! error TS2430: Index signatures are incompatible. !!! error TS2430: Type 'Base' is not assignable to type 'T'. [x: number]: Base; // error } interface B4 extends A { ~~ !!! error TS2430: Interface 'B4' incorrectly extends interface 'A'. !!! error TS2430: Index signatures are incompatible. !!! error TS2430: Type 'Derived' is not assignable to type 'T'. [x: number]: Derived; // error } interface B5 extends A { ~~ !!! error TS2430: Interface 'B5' incorrectly extends interface 'A'. !!! error TS2430: Index signatures are incompatible. !!! error TS2430: Type 'Derived2' is not assignable to type 'T'. [x: number]: Derived2; // error } }