---- Reported by luca.barbieri@gmail.com 2004-10-13 18:11:28 MST ----

Description of Problem:
The attached code doesn't work, which is astounding.


Steps to reproduce the problem:
1. Compile the C# code attached with CVS gmcs and run with CVS mono

Actual Results:
Unhandled Exception: System.InvalidCastException: Cannot cast from source
type to destination type.
in [0x00000] (at /home/lb/pers/src/test.cs:13) MainClass:Main (string[])

Expected Results:
No exceptions.


C# code:
class MainClass
{
        class Gen<T>
        {
        }

        class Der : Gen<int>
        {
        }

        static int Main(string[] args)
        {
                Gen<int> b = (Gen<int>)(object)new Der();
                return 0;
        }
}



Disassembled IL code:
.assembly extern mscorlib
{
  .ver 2:0:3600:0
  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 ) // .z\V.4..
}
.assembly 'test'
{
  .hash algorithm 0x00008004
  .ver  0:0:0:0
}
.module test.exe // GUID = {C792D86F-B92C-41AF-8420-E7F2C08BE1AD}


  .class private auto ansi beforefieldinit MainClass
        extends [mscorlib]System.Object
  {

    // method line 1
    .method public hidebysig  specialname  rtspecialname
           instance default void .ctor ()  cil managed
    {
        // Method begins at RVA 0x20ec
        // Code size 7 (0x7)
        .maxstack 8
        IL_0000:  ldarg.0
        IL_0001:  call instance void class [mscorlib]System.Object::.ctor()
        IL_0006:  ret
    } // end of method MainClass::instance default void .ctor ()

    // method line 2
    .method private static  hidebysig
           default int32 Main (string[] args)  cil managed
    {
        // Method begins at RVA 0x20f4
        .entrypoint
        // Code size 13 (0xd)
        .maxstack 2
        .locals init (
                class 'MainClass/Gen`1'<int32>  V_0)
        IL_0000:  newobj instance void class 'MainClass/Der'::.ctor()
        IL_0005:  castclass class 'MainClass/Gen`1'<int32>
        IL_000a:  stloc.0
        IL_000b:  ldc.i4.0
        IL_000c:  ret
    } // end of method MainClass::default int32 Main (string[] args)

  .class nested private auto ansi beforefieldinit 'Gen`1'<T>
        extends [mscorlib]System.Object
  {

    // method line 3
    .method public hidebysig  specialname  rtspecialname
           instance default void .ctor ()  cil managed
    {
        // Method begins at RVA 0x2110
        // Code size 7 (0x7)
        .maxstack 8
        IL_0000:  ldarg.0
        IL_0001:  call instance void class [mscorlib]System.Object::.ctor()
        IL_0006:  ret
    } // end of method Gen`1::instance default void .ctor ()

  } // end of class Gen`1

  .class nested private auto ansi beforefieldinit Der
        extends class 'MainClass/Gen`1'<int32>
  {

    // method line 4
    .method public hidebysig  specialname  rtspecialname
           instance default void .ctor ()  cil managed
    {
        // Method begins at RVA 0x2118
        // Code size 7 (0x7)
        .maxstack 8
        IL_0000:  ldarg.0
        IL_0001:  call instance void class 'MainClass/Gen`1'<int32>::.ctor()
        IL_0006:  ret
    } // end of method Der::instance default void .ctor ()

  } // end of class Der

  } // end of class MainClass



---- Additional Comments From luca.barbieri@gmail.com 2004-10-13 18:21:03 MST ----

It also fails if Gen<int> is replaced with Gen<REF_TYPE> where
REF_TYPE is a reference type, while of course it works if Gen<int> is
replaced with a non-generic type.




---- Additional Comments From martin@ximian.com 2004-10-13 18:44:03 MST ----

Very funny summary ;-)



---- Additional Comments From luca.barbieri@gmail.com 2004-10-13 19:02:11 MST ----

Are you sure that the problem is gmcs? The IL code it generates seems
correct.




---- Additional Comments From luca.barbieri@gmail.com 2004-10-13 19:12:30 MST ----

This code also FAILS:
class MainClass
{
	class Base
	{
	}
	
	class Gen<T> : Base
	{
	}

	class Der : Gen<int>
	{
	}

	static int Main(string[] args)
	{
		Base b = (Base)(object)new Der();
		return 0;
	}
}

And this too FAILS:
class MainClass
{
	class Base
	{
	}
	
	class Gen<T> : Base
	{
	}

	class Der<T> : Gen<T>
	{
	}

	static int Main(string[] args)
	{
		Gen<int> b = (Gen<int>)(object)new Der<int>();
		return 0;
	}
}




But this WORKS:
class MainClass
{
	class Base
	{
	}
	
	class Gen<T> : Base
	{
	}

	class Der<T> : Gen<T>
	{
	}

	static int Main(string[] args)
	{
		Base b = (Base)(object)new Der<int>();
		return 0;
	}
}


This also WORKS:
class MainClass
{
	class Base
	{
	}
	
	class Gen<T> : Base
	{
	}

	class Der<T> : Gen<int>
	{
	}

	static int Main(string[] args)
	{
		Base b = (Base)(object)new Der<int>();
		return 0;
	}
}


But very surprisingly this FAILS:
class MainClass
{
	class Base
	{
	}
	
	class Gen<T> : Base
	{
	}

	class Der : Gen<int>
	{
	}

	static int Main(string[] args)
	{
		Base b = (Base)(object)new Der();
		return 0;
	}
}




---- Additional Comments From martin@ximian.com 2004-10-13 19:36:09 MST ----

This is not a blocker, resetting priority.



---- Additional Comments From martin@ximian.com 2004-11-22 09:15:19 MST ----

Fixed in SVN.


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   <cf_op_sys_details>Fedora Development on Pentium M</cf_op_sys_details>
Unknown operating system unknown. Setting to default OS "Other".