Returns the type associated with this instruction.
LoadClass instances are always typed, but this type
does not always refer to the type of the class or interface
that it possibly forces to load. For example, GETFIELD would
return the type of the field and not the type of the class
where the field is defined.
If no class is forced to be loaded, null is returned.
An example for this is an ANEWARRAY instruction that creates
an int[][].