interface Foo {}
interface Foo extends {}
interface Bar extends Foo {}
interface Foo extends Array<number> {}
interface Foo extends Array<number | {}> {}
interface Foo extends Array<Bar> {}
interface Foo extends R {}
interface Foo<T> extends Bar<T> {}
declare module FooBar { type Baz = typeof baz; export interface Bar extends Baz {} }
interface Foo {

}

interface Foo { name: string; }
interface Foo { name: string; }
interface Bar { age: number; }

// valid because extending multiple interfaces can be used instead of a union type
interface Baz extends Foo, Bar {}
interface Foo { name: string; }
interface Foo { props: string; }
class Bar {}