genericParameterAssignability1.ts(1,26): error TS2322: Type 'null' is not assignable to type 'T'.
  'T' could be instantiated with an arbitrary type which could be unrelated to 'null'.


==== genericParameterAssignability1.ts (1 errors) ====
    function f<T>(x: T): T { return null; }
                             ~~~~~~
!!! error TS2322: Type 'null' is not assignable to type 'T'.
!!! error TS2322:   'T' could be instantiated with an arbitrary type which could be unrelated to 'null'.
    var r = <T>(x: T) => x;
    r = f; // should be allowed