==== tests/cases/compiler/constraints0.ts (1 errors) ====
    interface A {
        a: number;
    }
    
    interface B {
        b: string;
    }
    
    interface C<T extends A> {
        x: T;
    }
    
    var v1: C<A>; // should work
    var v2: C<B>; // should not work
            ~~~~
!!! constraints0.ts(14,9): error TS2086: Type 'B' does not satisfy the constraint 'A' for type parameter 'T extends A'.
    
    var y = v1.x.a; // 'a' should be of type 'number'