[Mono-list] foreach and GetEnumerator (with fixed test case)

Rodolfo Campero rodolfocampero@hotmail.com
Tue, 05 Oct 2004 23:10:40 +0000


I'm resending this email, this time with a sample that actually
reproduces the problem - I checked it in both MS .NET and mono

Sorry for the previous one.

Considering that the previous sample actually compiles and run in MS
.NET, now I'm thinking it's a bug in csc... anyway, I'd like to read
your comments, and if a mono hacker considers it's a mono bug, I can
file a bug report.

Here goes the testcase; it doesn't compile on Windows, but it does on
mono (if you run it, you'll get a NullReferenceException but that's ok):

compiled with:
Microsoft (R) Visual C# .NET Compiler version 7.00.9951
for Microsoft (R) .NET Framework version 1.0.3705

The error is in the line that contains the 'foreach' statement:

The call is ambiguous between the following methods or
properties: 'Testing.ICustomEnumerable.GetEnumerator()'
and 'System.Collections.IEnumerable.GetEnumerator()'

using System;
using System.Collections;

namespace Testing {
        interface ICustomEnumerable {
                IEnumerator GetEnumerator();

        interface IMixedEnumerable : IEnumerable, ICustomEnumerable {}

        class TestCollection : IMixedEnumerable {
                IEnumerator IEnumerable.GetEnumerator() {
                        return null;

                IEnumerator ICustomEnumerable.GetEnumerator()  {
                        return null;

        class Test {
                public static void Main(string[] args) {
                        IMixedEnumerable c = new TestCollection();
                        foreach(object o in c) {}

El lun, 04-10-2004 a las 20:04, Rodolfo Campero escribió:
>I've run into a situation with foreachs and the GetEnumerator method.
>The issue is reproduced with this small piece of code:

<the wrong example was removed/>

>This program can be compiled using mcs, and when I run it I get:
>         $ mono cols.exe
>         IEnumerable
>The problem is that this same piece of code won't compile in MS.NET csc
>compiler (I checked my original program with version 1.1, but not this
>simplified example): it complains that it can't choose between
>System.Collections.IEnumerable and IMyEnumerable.
>I'm rising this question because I'm not sure if this is a mono or a MS
>.NET bug, because I find the spec (ECMA-334, 15.8.4) rather ambiguous.
>At a given point it reads:
>         "A type C is said to be a collection type if it implements
>         "the System.IEnumerable interface or implements the collection
>         "pattern by meeting all of the following criteria: [...]"
>The thing is that it's not specified what happens when _both_ criteria
>are met.
>So, what do you think?
>Looking forward to reading all your comments,

MSN 8 with e-mail virus protection service: 2 months FREE*