==== tests/cases/compiler/genericDerivedTypeWithSpecializedBase2.ts (1 errors) ====
    class A<T extends { length: number }> {
        x: T;
    }
    
    class B<U> extends A<string> {
        y: U;
    }
    
    var x: A<{ length: number; foo: number }>;
    var y: B<number>;
    x = y;  // error
    ~
!!! genericDerivedTypeWithSpecializedBase2.ts(11,1): error TS2012: Cannot convert 'B<number>' to 'A<{ length: number; foo: number; }>':
!!! 	Types of property 'x' of types 'B<number>' and 'A<{ length: number; foo: number; }>' are incompatible:
!!! 		Type 'String' is missing property 'foo' from type '{ length: number; foo: number; }'.
    