[Ikvm-developers] Using Java annotation class fails with Mono.

[Dawid W. <daw...@cs...>]

Hi there,

I have a bug (?) I couldn't understand the source of, perhaps you'll share
my interest in finding out what's happening. We ikvm-compile a Java
annotation class that looks like this:

@Retention(RetentionPolicy.RUNTIME) @Target(ElementType.TYPE)
public @interface Bindable
{
   String prefix() default "";
}

then we place this annotation in C# code on a C# class:

namespace Org.Carrot2.Core
{
   [org.carrot2.util.attribute.Bindable(prefix = "component")]
   public class ComponentWithAttributes :
org.carrot2.core.ProcessingComponentBase
   [...]

This works like a charm with Microsoft .NET compiler, but fails with
mono (tried various revisions, the latest one Mono C# compiler version
2.6.7.0):

TypeAdaptersTest.cs(10,33): error CS0122:
`org.carrot2.util.attribute.BindableAttribute.prefix()' is
inaccessible due to its protection level
C:\PROGRA~2\MONO-2~1.7\lib\mono\2.0\gmcs.exe (Location of the symbol
related to previous error)
Compilation failed: 1 error(s), 0 warnings

When looking at the decompilation of BindableAttribute (which is the
annotation's implementation class generated by ikvm) one sees this:

   .method private newslot virtual final instance string prefix() cil managed
   {
      // ...
   }

   .property instance string prefix
   {
       .get instance string
org.carrot2.util.attribute.BindableAttribute::get_prefix()
       .set instance void
org.carrot2.util.attribute.BindableAttribute::set_prefix(string)
   }

I find the following things interesting:

a) prefix() is a virtual override, but is marked private? Is scope
limiting (as opposed to widening) possible at the CLR/CLI level? It's
quite interesting as to how and where this would apply to (after all,
you can always cast to the superclass/interface and then access the
method in question, right?).

b) C# compiler doesn't seem to accept a method and a property of the
same name to coexist. I assume that, again, the rules for CLR/CLI are
less restrictive than C# semantics (as it is the case with JVM and
Java), but my suspicion is that this confuses Mono and it takes the
methods as the first match, as opposed to the property getter, hence
the error above.

I uploaded a minimal example of the aforementioned problem here:

http://ophelia.cs.put.poznan.pl/~dweiss/download/

(the Java class is already compiled into Org.Carrot2.Core.dll, but I
can also provide the sources, should they be useful for anything. Full
compiler invocation line:

gmcs /target:library /reference:Org.Carrot2.Core.dll
/reference:IKVM.OpenJDK.Core.dll TypeAdaptersTest.cs

or

csc /target:library /reference:Org.Carrot2.Core.dll
/reference:IKVM.OpenJDK.Core.dll TypeAdaptersTest.cs

This isn't urgent my any means, but if anybody finds some time to
enlighten me, I'd be very grateful.

Dawid