// Call 'b.foo(1)' where class 'Foo' has an extension member 'fun B.invoke(Int)' should be checked two times for safe call (in 'checkReceiver'), because
// both 'b' (receiver) and 'foo' (this object) might be nullable. In the first case we mark dot, in the second 'foo'.
// Class 'CallForImplicitInvoke' helps up to recognise this case, and parameter 'implicitInvokeCheck' helps us to distinguish whether we check receiver or this object.