// @target: esnext // @declaration: true interface Mixin { mixinMethod(): void; } function Mixin any>(baseClass: TBaseClass): TBaseClass & (abstract new (...args: any) => Mixin) { // error expected: A mixin class that extends from a type variable containing an abstract construct signature must also be declared 'abstract'. class MixinClass extends baseClass implements Mixin { mixinMethod() { } } return MixinClass; } abstract class AbstractBase { abstract abstractBaseMethod(): void; } const MixedBase = Mixin(AbstractBase); // error expected: Non-abstract class 'DerivedFromAbstract' does not implement inherited abstract member 'abstractBaseMethod' from class 'AbstractBase & Mixin'. class DerivedFromAbstract extends MixedBase { } // error expected: Cannot create an instance of an abstract class. new MixedBase();