a.ts(1,14): error TS2564: Property 'a' has no initializer and is not definitely assigned in the constructor.


==== a.ts (1 errors) ====
    class C<T> { a: T; }
                 ~
!!! error TS2564: Property 'a' has no initializer and is not definitely assigned in the constructor.
    
==== b.ts (0 errors) ====
    interface C<T> { }