=== tests/cases/compiler/promisesWithConstraints.ts ===
interface Promise<T> {
>Promise : Symbol(Promise, Decl(promisesWithConstraints.ts, 0, 0))
>T : Symbol(T, Decl(promisesWithConstraints.ts, 0, 18))

    then<U>(cb: (x: T) => Promise<U>): Promise<U>;
>then : Symbol(then, Decl(promisesWithConstraints.ts, 0, 22))
>U : Symbol(U, Decl(promisesWithConstraints.ts, 1, 9))
>cb : Symbol(cb, Decl(promisesWithConstraints.ts, 1, 12))
>x : Symbol(x, Decl(promisesWithConstraints.ts, 1, 17))
>T : Symbol(T, Decl(promisesWithConstraints.ts, 0, 18))
>Promise : Symbol(Promise, Decl(promisesWithConstraints.ts, 0, 0))
>U : Symbol(U, Decl(promisesWithConstraints.ts, 1, 9))
>Promise : Symbol(Promise, Decl(promisesWithConstraints.ts, 0, 0))
>U : Symbol(U, Decl(promisesWithConstraints.ts, 1, 9))
}

interface CPromise<T extends { x: any; }> {
>CPromise : Symbol(CPromise, Decl(promisesWithConstraints.ts, 2, 1))
>T : Symbol(T, Decl(promisesWithConstraints.ts, 4, 19))
>x : Symbol(x, Decl(promisesWithConstraints.ts, 4, 30))

    then<U extends { x: any; }>(cb: (x: T) => Promise<U>): Promise<U>;
>then : Symbol(then, Decl(promisesWithConstraints.ts, 4, 43))
>U : Symbol(U, Decl(promisesWithConstraints.ts, 5, 9))
>x : Symbol(x, Decl(promisesWithConstraints.ts, 5, 20))
>cb : Symbol(cb, Decl(promisesWithConstraints.ts, 5, 32))
>x : Symbol(x, Decl(promisesWithConstraints.ts, 5, 37))
>T : Symbol(T, Decl(promisesWithConstraints.ts, 4, 19))
>Promise : Symbol(Promise, Decl(promisesWithConstraints.ts, 0, 0))
>U : Symbol(U, Decl(promisesWithConstraints.ts, 5, 9))
>Promise : Symbol(Promise, Decl(promisesWithConstraints.ts, 0, 0))
>U : Symbol(U, Decl(promisesWithConstraints.ts, 5, 9))
}

interface Foo { x; }
>Foo : Symbol(Foo, Decl(promisesWithConstraints.ts, 6, 1))
>x : Symbol(x, Decl(promisesWithConstraints.ts, 8, 15))

interface Bar { x; y; }
>Bar : Symbol(Bar, Decl(promisesWithConstraints.ts, 8, 20))
>x : Symbol(x, Decl(promisesWithConstraints.ts, 9, 15))
>y : Symbol(y, Decl(promisesWithConstraints.ts, 9, 18))

var a: Promise<Foo>;
>a : Symbol(a, Decl(promisesWithConstraints.ts, 11, 3))
>Promise : Symbol(Promise, Decl(promisesWithConstraints.ts, 0, 0))
>Foo : Symbol(Foo, Decl(promisesWithConstraints.ts, 6, 1))

var b: Promise<Bar>;
>b : Symbol(b, Decl(promisesWithConstraints.ts, 12, 3))
>Promise : Symbol(Promise, Decl(promisesWithConstraints.ts, 0, 0))
>Bar : Symbol(Bar, Decl(promisesWithConstraints.ts, 8, 20))

a = b; // ok
>a : Symbol(a, Decl(promisesWithConstraints.ts, 11, 3))
>b : Symbol(b, Decl(promisesWithConstraints.ts, 12, 3))

b = a; // ok
>b : Symbol(b, Decl(promisesWithConstraints.ts, 12, 3))
>a : Symbol(a, Decl(promisesWithConstraints.ts, 11, 3))

var a2: CPromise<Foo>;
>a2 : Symbol(a2, Decl(promisesWithConstraints.ts, 16, 3))
>CPromise : Symbol(CPromise, Decl(promisesWithConstraints.ts, 2, 1))
>Foo : Symbol(Foo, Decl(promisesWithConstraints.ts, 6, 1))

var b2: CPromise<Bar>;
>b2 : Symbol(b2, Decl(promisesWithConstraints.ts, 17, 3))
>CPromise : Symbol(CPromise, Decl(promisesWithConstraints.ts, 2, 1))
>Bar : Symbol(Bar, Decl(promisesWithConstraints.ts, 8, 20))

a2 = b2; // ok
>a2 : Symbol(a2, Decl(promisesWithConstraints.ts, 16, 3))
>b2 : Symbol(b2, Decl(promisesWithConstraints.ts, 17, 3))

b2 = a2; // was error
>b2 : Symbol(b2, Decl(promisesWithConstraints.ts, 17, 3))
>a2 : Symbol(a2, Decl(promisesWithConstraints.ts, 16, 3))