---- Reported by nazgul@omega.pl 2005-02-10 09:30:55 MST ----

Please fill in this template when reporting a bug, unless you know what you
are doing.
Description of Problem:
I got exception from gmcs for code, which work on MS.NET Beta1

Steps to reproduce the problem:
1. Try to compile this program:

using System.Collections.Generic;

// comment this line to see another bug in gmcs (unrelated)
interface IB { bool foo (); }


class B : IB { public bool foo () { return true; } }

interface Filter <T> where T : IB {
  T Is (IB x);

}

struct K : IB {
  public bool foo () { return false; }

}

class MyFilter : Filter <K> {
  public K Is (IB x) { return new K(); }
}

class MyBFilter : Filter <B> {
  public B Is (IB x) { return new B(); }
}

class M {
 
  static List<T> foo1 <T> (Filter <T> x) where T : IB {
    List <T> result = new List <T>();
    T maybe = x.Is (new B());
    if (maybe != null)
      result.Add (maybe);
    return result;
  }
 
  static void Main () {
       MyFilter m = new MyFilter ();
        System.Console.WriteLine (foo1 <K> (m).Count);
        MyBFilter mb = new MyBFilter ();
        System.Console.WriteLine (foo1 <B> (mb).Count);
  }
}


Actual Results:

Unhandled Exception: System.NullReferenceException: Object reference not
set to an instance of an object
in <0x000fc> Mono.CSharp.GenericConstraints:get_IsReferenceType ()
in <0x000a0> Mono.CSharp.Convert:ImplicitTypeParameterConversion
(Mono.CSharp.EmitContext,Mono.CSharp.Expression,System.Type)
in <0x00045> Mono.CSharp.Convert:ImplicitReferenceConversionExists
(Mono.CSharp.EmitContext,Mono.CSharp.Expression,System.Type)
in <0x003c3> Mono.CSharp.Convert:ImplicitStandardConversionExists
(Mono.CSharp.EmitContext,Mono.CSharp.Expression,System.Type)
in <0x00173> Mono.CSharp.ConstructedType:CheckConstraint
(Mono.CSharp.EmitContext,System.Type,Mono.CSharp.Expression,System.Type)
in <0x00368> Mono.CSharp.ConstructedType:CheckConstraints
(Mono.CSharp.EmitContext,int)
in <0x0001b> Mono.CSharp.ConstructedType:CheckConstraints
(Mono.CSharp.EmitContext)
in <0x00026> Mono.CSharp.ConstructedType:ResolveAsTypeTerminal
(Mono.CSharp.EmitContext)
in <0x00021> Mono.CSharp.Parameter:Resolve
(Mono.CSharp.EmitContext,Mono.CSharp.Location)
in <0x000ef> Mono.CSharp.Parameters:ComputeParameterTypes
(Mono.CSharp.EmitContext)
in <0x00033> Mono.CSharp.Parameters:GetParameterInfo (Mono.CSharp.EmitContext)
in <0x00067> Mono.CSharp.MethodCore:DoDefineParameters ()
in <0x0003a> Mono.CSharp.MethodCore:CheckBase ()
in <0x000ac> Mono.CSharp.Method:Define ()
in <0x00077> MemberCoreArrayList:DefineContainerMembers ()
in <0x00010> MethodArrayList:DefineContainerMembers ()
in <0x00014> Mono.CSharp.TypeContainer:DefineContainerMembers
(Mono.CSharp.TypeContainer/MemberCoreArrayList)
in <0x004ef> Mono.CSharp.TypeContainer:DoDefineMembers ()
in <0x0002b> Mono.CSharp.TypeContainer:DefineMembers
(Mono.CSharp.TypeContainer)
in <0x00284> Mono.CSharp.RootContext:PopulateTypes ()
in <0x00b46> Mono.CSharp.Driver:MainDriver (string[])
in <0x0001f> Mono.CSharp.Driver:Main (string[])


Expected Results:
Compilation succeeded and 
1
1
when program is run

How often does this happen? 
Always

Additional Information:
(try commenting IB interface definition to see some other crash, which
happens after error message is given - probably it should be filed as
another bug)



---- Additional Comments From martin@ximian.com 2005-02-21 20:01:58 MST ----

I'm almost done with a fix, but too tired to finish it tonight.
Will fix it tomorrow morning.



---- Additional Comments From martin@ximian.com 2005-02-22 15:35:59 MST ----

Fixed in SVN (both issues).


Unknown bug field "cf_op_sys_details" encountered while moving bug
   <cf_op_sys_details>Mandrake Linux 10.1</cf_op_sys_details>
Unknown bug field "cf_version_details" encountered while moving bug
   <cf_version_details>mono from svn (about 2 Feb)</cf_version_details>
Unknown operating system unknown. Setting to default OS "Other".