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Bug 327508

Summary:	[Polymorphic Dispatcher] null values should be handled as compatible by default
Product:	[Modeling] TMF	Reporter:	Sven Efftinge <sven.efftinge>
Component:	Xtext	Assignee:	Project Inbox <tmf.xtext-inbox>
Status:	CLOSED FIXED	QA Contact:
Severity:	normal
Priority:	P3	CC:	sebastian.zarnekow
Version:	2.0.0	Flags:	sven.efftinge: indigo+
Target Milestone:	M3
Hardware:	PC
OS:	Mac OS X - Carbon (unsup.)
Whiteboard:

Description Sven Efftinge

2010-10-12 02:28:12 EDT

In case a null reference is passed as an argument to invoke, getDefaultClass(int) is called in order to
allow to map null to a certain default type. 
That might be useful, but mapping any nulls to Object.class by default is wrong, since null is a member of any reference type. Instead the method should return null by default and the dispatcher should handle
null as compatible to any reference type.

Comment 1 Sebastian Zarnekow

2010-10-12 02:51:54 EDT

Should be dispatch null-params to method(Void v) ?

Comment 2 Sebastian Zarnekow

2010-10-12 02:52:17 EDT

Sorry, typo:

Should we dispatch null-params to method(Void v) ?

Comment 3 Sven Efftinge

2010-10-12 03:11:29 EDT

If we would assume Void.class for any nulls in Java, the client would always have to specify such a method signature. This is because Void has no super type (other than Object).
We could of course mimic that Void is a subtype of everything, but that would complicate things and I'm not sure it is worth it.

Comment 4 Sebastian Zarnekow

2010-10-12 03:18:50 EDT

Agreed.

So by default you'd actually not call any method if null is passed to the dispatcher and more than one possibility exists?

Comment 5 Sven Efftinge

2010-10-12 03:22:55 EDT

By default the most specific signature is called (like it is with any other arguments) and in case there is no single most specific and error is raised.

I'm not completely sure that being able to explicitly fetch null arguments by adding a signature for Void couldn't be useful. In Xtend I used that feature quite often. Maybe we should do it someday...

Comment 6 Sven Efftinge

2010-10-12 04:40:51 EDT

Changed the semantics, such that Void can be used to fetch null arguments.

Comment 7 Karsten Thoms

2017-09-19 17:24:52 EDT

Closing all bugs that were set to RESOLVED before Neon.0

Comment 8 Karsten Thoms

2017-09-19 17:36:33 EDT

Closing all bugs that were set to RESOLVED before Neon.0