t1.a is equivalent to TestClass1.a in this case, since a is a static member (not an instance member). The compiler looks at the declaration of t1 to see what type it is, and then just treats it as if you had used the type name. The value of t1 is never checked. (But if it were a method call, like method(args).a, I think the method would be called. But the return value would be thrown away, and never checked.) (Edit: I've verified that method(args) is called, but no exception is thrown if the function result is null.)
