tests/cases/compiler/promisesWithConstraints.ts(15,1): error TS2322: Type 'Promise<Foo>' is not assignable to type 'Promise<Bar>'.
  Property 'y' is missing in type 'Foo' but required in type 'Bar'.
tests/cases/compiler/promisesWithConstraints.ts(20,1): error TS2322: Type 'CPromise<Foo>' is not assignable to type 'CPromise<Bar>'.
  Type 'Foo' is not assignable to type 'Bar'.


==== tests/cases/compiler/promisesWithConstraints.ts (2 errors) ====
    interface Promise<T> {
        then<U>(cb: (x: T) => Promise<U>): Promise<U>;
    }
    
    interface CPromise<T extends { x: any; }> {
        then<U extends { x: any; }>(cb: (x: T) => Promise<U>): Promise<U>;
    }
    
    interface Foo { x; }
    interface Bar { x; y; }
    
    var a: Promise<Foo>;
    var b: Promise<Bar>;
    a = b; // ok
    b = a; // ok
    ~
!!! error TS2322: Type 'Promise<Foo>' is not assignable to type 'Promise<Bar>'.
!!! error TS2322:   Property 'y' is missing in type 'Foo' but required in type 'Bar'.
!!! related TS2728 tests/cases/compiler/promisesWithConstraints.ts:10:20: 'y' is declared here.
    
    var a2: CPromise<Foo>;
    var b2: CPromise<Bar>;
    a2 = b2; // ok
    b2 = a2; // was error
    ~~
!!! error TS2322: Type 'CPromise<Foo>' is not assignable to type 'CPromise<Bar>'.
!!! error TS2322:   Type 'Foo' is not assignable to type 'Bar'.
    