[Mono-bugs] [Bug 668652] New: Mono fails to compile class using LINQ query pattern

bugzilla_noreply at novell.com bugzilla_noreply at novell.com
Tue Feb 1 11:32:22 EST 2011



           Summary: Mono fails to compile class using LINQ query pattern
    Classification: Mono
           Product: Mono: Compilers
           Version: 2.8.x
          Platform: i686
        OS/Version: Linux
            Status: NEW
          Severity: Major
          Priority: P5 - None
         Component: C#
        AssignedTo: msafar at novell.com
        ReportedBy: justin_bailey at adp.com
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---
           Blocker: ---

Created an attachment (id=411554)
 --> (http://bugzilla.novell.com/attachment.cgi?id=411554)
Program.cs as described in the bug report.

User-Agent:       Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0b10) Gecko/20100101

The class below will compile fine with CSC, but not dmsc (or gmsc, or msc). The
class implements the "query pattern pattern" for LINQ (described in section
7.15.3 of the C# 3.0 spec), so it's not anything too weird.

Removing the "using System.Linq" import will get rid of one error, but it still
doesn't fix the problem. Even so, the class compiles fine with Microsoft's

Reproducible: Always

Steps to Reproduce:
1. Save the following class in file named Program.cs:

using System;
using System.Linq;

namespace MonoLinq
    class Program
        static void Main(string[] args)
            var server = new Server<int>();
            var outputExpr1 = from item in server
                                where item.Is()
                                select item;

            var foo = server.Where(p => p.Is());

            Console.WriteLine("outputExpr1.GetType: {0}",
            Console.WriteLine("foo.GetType: {0}", foo.GetType().FullName);

    class Server<T>
        public Server()

        public string Where(Func<IDAccessor, string> idExpr)
            return String.Empty;

    class IDAccessor

    static class IDAccessorExt
        public static string Is(this IDAccessor __)
            return null;

2. Compile with this command line:

  dmcs Program.cs

Actual Results:  
The compiler will give the following errors:

Program.cs(12,33): error CS0411: The type arguments for method
System.Collections.Generic.IEnumerable<TSource>, System.Func<TSource,bool>)'
cannot be inferred from the usage. Try specifying the type arguments explicitly
Program.cs(12,44): error CS0029: Cannot implicitly convert type `string' to

Expected Results:  
The program should compile.

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