[foreign] Improve error reporting when Java signature and native function layout don't match.

[Jorn Vernee]

Maurizio Cimadamore schreef op 2018-09-26 17:49:
>> I also made it so that `nullPointer()` takes a LayoutType, so that a 
>> method returning e.g. `Pointer<Integer>` doesn't suddenly have a 
>> LayoutType with a Void carrier. Seeing the References.ofVoid anonymous 
>> class in the stack trace was also a source of confusion for me.
> Not sure you need to add a parameter to nullPointer for that. I think
> there should be only one null pointer, and we should use unchecked
> conversion internally to cast it to the type the user wants -
> dynamically the carrier will not be used - since the Reference
> attached to that will prevent dereference ops.

Yeah, you're right, it wasn't needed in the end [1]. I did create a 
BoundedPointer.nullPointer() as well so I wouldn't have to make the 
LayoutTypeImpl constructor public. That also allowed me to simplify the 
type variable declaration, since the one place that needed a null 
BoundedPointer can now just call BoundedPointer.nullPointer().

I also removed the type parameter from the carrier field in 
LayoutTypeImpl, since it didn't really seem to be used, as 
LayoutTypeImpl.carrier() just returned a Class<?>. That allowed me to 
avoid doing an unchecked cast in BoundedPointer.nullPointer().

Jorn

[1] : 
https://gist.github.com/JornVernee/7727db9b8ebdbb5c88205e3bbe97227c