---- Reported by pawel.sakowski@mindbreeze.com 2007-01-26 05:35:48 MST ----

Description of Problem:
In certain cases, gmcs isn't able to compile a foreach enumeration over a
generic collection, emitting confusing messages regarding ambiguity of
GetEnumerator(). The messages can be both warnings and errors. An example
of both cases follows (I considered these related, so posting as a single
bug report).

Steps to reproduce the problem:
1. Download and unpack http://www.itu.dk/research/c5/Release1.0/C5.bin.zip
2. Create ambiguous-enumerable-warning.cs:

using System.Collections.Generic;
class X{static void Main(){
IDictionary<int,int> dict = new Dictionary<int,int>();
foreach (KeyValuePair<int,int> pair in dict) {
System.Console.WriteLine(pair.Key);
}
}}

3. Create ambiguous-enumerable-error.cs:

public class A: C5.ArrayList<int> {}
class X{static void Main(){
A x = new A();
foreach (int i in x) {
}
}}

4. gmcs -warnaserror ambiguous-enumerable-warning.cs
5. gmcs /r:C5.dll ambiguous-enumerable-error.cs

Actual Results:
ambiguous-enumerable-warning.cs(4,1): error CS0278:
`System.Collections.Generic.IDictionary<int,int>' contains ambiguous
implementation of `enumerable' pattern. Method
`System.Collections.IEnumerable.GetEnumerator()' is ambiguous with method
`System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<int,int>>.GetEnumerator()'
/usr/lib/mono/2.0/mscorlib.dll (Location of the symbol related to previous
error)
/usr/lib/mono/2.0/mscorlib.dll (Location of the symbol related to previous
error)
Compilation failed: 1 error(s), 0 warnings

ambiguous-enumerable-error.cs(5,1): error CS1640: foreach statement cannot
operate on variables of type `A' because it contains multiple
implementation of `C5.ArrayBase<int>.GetEnumerator()'. Try casting to a
specific implementation
ambiguous-enumerable-error.cs(1,14): (Location of the symbol related to
previous error)
Compilation failed: 1 error(s), 0 warnings

Expected Results:
Two successes.

How often does this happen? 
100%

Additional Information:
Reproduces with mono 1.2.2.1
The test cases compile fine with both csc and mono 1.1.13.6.



---- Additional Comments From pawel.sakowski@mindbreeze.com 2007-01-26 09:27:44 MST ----

In case it's unclear:

The expected results are not to produce any message (warning or error)
on the foreach lines.



---- Additional Comments From rharinath@novell.com 2007-01-27 12:21:50 MST ----

I believe this has been fixed recently (though I haven't downloaded
the testcase yet).  Can you retry with a recent SVN snapshot and/or
the 1.2.3 pretest?



---- Additional Comments From gert.driesen@pandora.be 2007-01-28 13:49:11 MST ----

The first issue (CS2078) is indeed resolved in SVN, however I can 
still reproduce the second issue (CS1640).



---- Additional Comments From martin@ximian.com 2007-04-03 15:14:15 MST ----

Fixed in SVN.



---- Additional Comments From martin@ximian.com 2007-04-03 15:14:42 MST ----

.