==== tests/cases/compiler/genericDerivedTypeWithSpecializedBase.ts (1 errors) ====
    class A<T> {
        x: T;
    }
    
    class B<U> extends A<string> {
        y: U;
    }
    
    var x: A<number>;
    var y: B<number>;
    x = y;  // error
    ~
!!! genericDerivedTypeWithSpecializedBase.ts(11,1): error TS2012: Cannot convert 'B<number>' to 'A<number>':
!!! 	Types of property 'x' of types 'B<number>' and 'A<number>' are incompatible.
    