PR# 4045 Assignment attempt should be Void, but eventually causes InvalidCastException in .NET

I've run into an invalid cast exception while running a .NET application
that I'm developing. The bug is demonstrated by the the classes below. These
same classes behave correctly in a classic application.

This looks a bit like a catcall, but it isn't. The actual type of 'p' is
CHILD. The assignment attempt (p ?= a) tries to store a CHILD2 object in p.
In a classic application, p is Void. But in .NET, it merrily sets the CHILD2
object, and when the caller tries to access the wrongly assigned 'p' it
throws an InvalidCastException.

class APPLICATION
      create make
      feature {NONE} make is
            local
                  b: BUG [CHILD]
                  c: CHILD
            do
                  create b.make (create {CHILD2})
                  c := b.p -- InvalidCastException in .NET
            end
end

class PARENT end

class CHILD inherit PARENT end

class CHILD2 inherit PARENT end

class BUG [reference G -> PARENT]
      create make
      feature {NONE} make (a: PARENT) is
            do p ?= a end -- Should be Void
      feature p: G
end

From: Peter Gummer <pgummer@decisions-made-easy.com.au>
To: bugs@support.eiffel.com
Cc: 
Subject: RE: EiffelStudio/4045 - Assignment attempt should be Void, but ev
	entually causes InvalidCastException in .NET
Date: Tue, 5 Apr 2005 09:13:24 +1000 

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 Hi,
 
 This error is still happening in 5.6.0721.
 
 - Peter Gummer
 
 
 -----Original Message-----
 From: bugs@berkeley.eiffel.com [mailto:bugs@berkeley.eiffel.com] 
 Sent: Wednesday, 22 September 2004 10:24
 To: pgummer@decisions-made-easy.com.au
 Subject: EiffelStudio/4045
 
 Thank you very much for your problem report.
 It has the internal identification `EiffelStudio/4045'.
 
 If you want to add more information to your report or
 reply to our answer, please reply to this message
 without modifying the subject header.
 
 The individual assigned to look a
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