[Mono-bugs] [Bug 368455] New: ArrayList.Sort() throws exception with incorrect message

[bugzilla_noreply at novell.com]

https://bugzilla.novell.com/show_bug.cgi?id=368455


           Summary: ArrayList.Sort() throws exception with incorrect message
           Product: Mono: Class Libraries
           Version: 1.2.6
          Platform: i686
        OS/Version: Linux
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: System
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: dbera.web at gmail.com
         QAContact: mono-bugs at lists.ximian.com
          Found By: Customer


Trying to use an ArrayList of objects that defines a generic IComparer<T> (but
not IComparable) and then sorting the list crashes as expected (as I was told
in the IRC). However, the error message says "No IComparable or IComparable<T>
interface found for..." which is incorrect and confusing since the objects
clearly implement IComparable<T>.

$ cat testlist.cs
using System;
using System.Collections.Generic;

class test {
    class obj : IComparable<obj> {
        public int CompareTo (obj other)
        {
            return 1;
        }
    }

    public static void Main ()
    {
        System.Collections.ArrayList list = new System.Collections.ArrayList
();
        list.Add (new obj ());
        list.Add (new obj ());
        list.Sort ();
    }
}

$ mono testlist.exe

Unhandled Exception: System.InvalidOperationException: The comparer threw an
exception. ---> System.InvalidOperationException: No IComparable or
IComparable<T> interface found for type 'System.Object'.
  at System.Array.compare[Object] (System.Object value1, System.Object value2,
IComparer`1 comparer) [0x00000]
  at System.Array.qsort[Object,Object] (System.Object[] keys, System.Object[]
items, Int32 low0, Int32 high0, IComparer`1 comparer) [0x00000]
  at System.Array.Sort[Object,Object] (System.Object[] keys, System.Object[]
items, Int32 index, Int32 length, IComparer`1 comparer) [0x00000] --- End of
inner exception stack trace ---

  at System.Array.Sort[Object,Object] (System.Object[] keys, System.Object[]
items, Int32 index, Int32 length, IComparer`1 comparer) [0x00000]
  at System.Array.Sort[Object] (System.Object[] array, Int32 index, Int32
length) [0x00000]
  at System.Collections.ArrayList.Sort () [0x00000]
  at test.Main () [0x00000]


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