In the specification, section 6.3 (page 75 of the May 24, 2011 draft) it says:

The null value is of type scala.Null, and is thus compatible with every reference type. It denotes a reference value which refers to a special "null" object. This object implements methods in class scala.AnyRef as follows:

• ...
• asInstanceOf[T] returns the "null" object itself if T conforms to scala.AnyRef, and throws a NullPointerException otherwise.

Yet null.asInstanceOf[Int\] returns 0 instead of throwing an exception. Either the compiler is wrong or the spec needs to be updated.

This was found by 爱国者 on http://stackoverflow.com/questions/8285916/why-doesnt-null-asinstanceofint-throw-a-nullpointerexception