---- Reported by dsilva@ccs.neu.edu 2005-05-27 15:50:30 MST ----

Description of Problem:

I don't know if this is a bug in gmcs, the runtime, or the class library.

Sample program:

$ cat eq.cs
using System.Collections.Generic;
using Mono.Cecil;

public class App {
  public static void Main() {
    IDictionary<ITypeReference, string> typenames
                 = new Dictionary<ITypeReference, string>();
    string typename = typenames[null];
  }
}

$ gmcs -debug -r:/home/dsilva/cvs/mono-svn/cecil/lib/Mono.Cecil.dll  eq.cs
eq.cs(8) warning CS0219: The variable 'typename' is assigned but its value
is never used
Compilation succeeded - 1 warning(s)



$ mono --debug eq.exe
** (eq.exe:12910): WARNING **: Missing method Equals in assembly
/usr/local/stow/mono-svn/lib/mono/2.0/mscorlib.dll token 6000002

Unhandled Exception: System.NullReferenceException: Object reference not
set to an instance of an object
in <0x00000> <unknown method>
in [0x0000c] (at
/home/dsilva/cvs/mono-svn/mcs/class/corlib/System.Collections.Generic/Dictionary.cs:87)
System.Collections.Generic.Dictionary`2<Mono.Cecil.ITypeReference,System.String>:get_Item
(ITypeReference )
in [0x00008] (at /tmp/eq.cs:9) App:Main ()


So I changed the constructors for NullReferenceException to print a stack
trace, then changed Dictionary.cs's index operator like this:

  public V this [K key] {
   get {
    System.Console.WriteLine("Dictionary.get_Item: entry");
    int index = GetSlot (key);
    System.Console.WriteLine("Dictionary.get_Item: got the index");
    if (index < 0) {
      System.Console.WriteLine("Dictionary.get_Item: index is invalid");
      throw new KeyNotFoundException ();
      }
    System.Console.WriteLine("Dictionary.get_Item: index is valid");
    return _table [index].Value;
  }


then changed mono/metadata/loader.c's mono_get_method_constrained procedure
to log a couple more things after the find_method call:

result = find_method (constrained_class, ic, method->name,
mono_method_signature (method));
if (!result) {
  g_warning("Constrained class address: 0x%x, ic address: 0x%x",
             (unsigned int) constrained_class, (unsigned int) ic);
  g_warning("Constrained class name address: 0x%x, ic name address: 0x%x",
             (unsigned int) constrained_class->name,
             (ic ? (unsigned int) ic->name : 0));
  g_warning("Constrained class: %s, ic: %s", constrained_class->name,
             (ic ? ic->name : "(no name, ic is null)"));
  g_warning ("Missing method %s in assembly %s token %x", method->name,
              image->name, token);
}


then ran the program again:

$ mono --debug eq.exe

         at System.NullReferenceException..ctor ()
Dictionary.get_Item: entry

** (eq.exe:12910): WARNING **: Constrained class address: 0x82af728, ic
address: 0x0

** (eq.exe:12910): WARNING **: Constrained class name address: 0xb72663aa,
ic name address: 0x0

** (eq.exe:12910): WARNING **: Constrained class: ITypeReference, ic: (no
name, ic is null)

** (eq.exe:12910): WARNING **: Missing method Equals in assembly
/usr/local/stow/mono-svn/lib/mono/2.0/mscorlib.dll token 6000002

         at System.NullReferenceException..ctor ()
         at System.Collections.Generic.Dictionary`2.get_Item ()
         at System.Collections.Generic.Dictionary`2.get_Item ()
         at App.Main ()

Unhandled Exception: System.NullReferenceException: Object reference not
set to an instance of an object
in <0x00000> <unknown method>
in [0x0000c] (at
/home/dsilva/cvs/mono-svn/mcs/class/corlib/System.Collections.Generic/Dictionary.cs:87)
System.Collections.Generic.Dictionary`2<Mono.Cecil.ITypeReference,System.String>:get_Item
(ITypeReference )
in [0x00008] (at /tmp/eq.cs:9) App:Main ()
$


Note: I used Cecil's ITypeReference in the bug report because the problem
doesn't appear when I use a value type or a class defined in the same file.



---- Additional Comments From dsilva@ccs.neu.edu 2005-05-27 15:52:51 MST ----

By the way, the error shows up regardless of whether the key is null
or not.



---- Additional Comments From martin@ximian.com 2005-07-02 09:08:16 MST ----

The NullReferenceException is clearly NOTABUG.

The `cannot find method' error in mono_find_method_constrained() is a
duplicate of bug .... (forgot the bug number) .... I fixed yesterday.



---- Additional Comments From martin@ximian.com 2005-07-02 09:11:16 MST ----

The Nemerle guys were so nice of mentioning that bug # I was looking
for in their blog - this one is a duplicate of #75429 :-)




---- Additional Comments From martin@ximian.com 2005-07-02 09:11:30 MST ----



*** This bug has been marked as a duplicate of https://bugzilla.novell.com/show_bug.cgi?id=MONO75429 ***


Unknown operating system unknown. Setting to default OS "Other".
This bug was marked DUPLICATE in the database it was moved from.
    Changing resolution to "MOVED"