[Mono-bugs] [Bug 568955] System.InvalidOperationException: List has changed. from gmcs while compiling.

[bugzilla_noreply at novell.com]

http://bugzilla.novell.com/show_bug.cgi?id=568955

http://bugzilla.novell.com/show_bug.cgi?id=568955#c5


Pablo Ruiz <pruiz at netway.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #355170|0                           |1
        is obsolete|                            |

--- Comment #5 from Pablo Ruiz <pruiz at netway.org> 2010-04-20 13:59:18 UTC ---
Created an attachment (id=355584)
 --> (http://bugzilla.novell.com/attachment.cgi?id=355584)
List changed work-a-round v2.

Here it's an updated work-a-round which avoids the 'List changed' problem, but
does not fully resolve the Bug, as the compiled code wont work either, as the
generated Expression is invalid.

You can reproduce the new fault compiling the following code:

-----------
using System;
using System.Linq;
using System.Linq.Expressions;
using System.Diagnostics;

namespace Test
{
        public class Rate
        {
                public int Id { get; set; }
        }

        public class Specification
        {
                public Expression<Func<Rate, bool>> expression;
                public Func<Rate, bool> fn;

                public Specification(Expression<Func<Rate, bool>> predicate)
                {
                        this.expression = predicate;
                        this.fn = predicate.Compile() as Func<Rate, bool>;
                }
        }

        public class RateById : Specification
        {
                public RateById(int id)
                        : base(x => x.Id == id)
                {
                }
        }

        public class Program
        {
                static void Main()
                {
                        var obj = new Rate() { Id = 1 };

                        var s1 = new RateById(1);
                        var s2 = new RateById(2);

                        Debug.Assert(s1.fn.Invoke(obj) == true);
                        Debug.Assert(s2.fn.Invoke(obj) == false);
                }
        }
}
----------

gmcs /target:exe p.cs && mono ./p.exe

Unhandled Exception: System.ArgumentNullException: Argument cannot be null.
Parameter name: expression
  at System.Linq.Expressions.Expression.Property
(System.Linq.Expressions.Expression expression, System.Reflection.MethodInfo
propertyAccessor) [0x00080] in
/usr/src/redhat/BUILD/mono-2.6.3/mcs/class/System.Core/System.Linq.Expressions/Expression.cs:2112
  at Test.RateById..ctor (Int32 id) [0x00000] in <filename unknown>:0
  at Test.Program.Main () [0x00000] in <filename unknown>:0

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