a.ts(1,35): error TS2564: Property 'a' has no initializer and is not definitely assigned in the constructor.


==== a.ts (1 errors) ====
    export default abstract class A { a: number; }
                                      ~
!!! error TS2564: Property 'a' has no initializer and is not definitely assigned in the constructor.
    
    class B extends A {}
    new B().a.toExponential();
    
==== b.ts (0 errors) ====
    import A from './a';
    
    class C extends A {}
    new C().a.toExponential();