IsWellKnownTypeUnmanagedType helper in C# compiler fails to filter out generic types.

[AlekseyTs]

The following test passes but it should produce an error on obj.M1<int>():

        [Fact]
        public void LoadingUnmanagedTypeModifier_ModreqGeneric()
        {
            var ilSource = IsUnmanagedAttributeIL + @"
.class public auto ansi beforefieldinit TestRef
       extends [mscorlib]System.Object
{
  .method public hidebysig instance void
          M1<valuetype .ctor (class [mscorlib]System.ValueType modreq(System.Runtime.InteropServices.UnmanagedType`1)) T>() cil managed
  {
    .param type T
    .custom instance void System.Runtime.CompilerServices.IsUnmanagedAttribute::.ctor() = ( 01 00 00 00 )
    // Code size       2 (0x2)
    .maxstack  8
    IL_0000:  nop
    IL_0001:  ret
  } // end of method TestRef::M1

  .method public hidebysig specialname rtspecialname
          instance void  .ctor() cil managed
  {
    // Code size       8 (0x8)
    .maxstack  8
    IL_0000:  ldarg.0
    IL_0001:  call       instance void [mscorlib]System.Object::.ctor()
    IL_0006:  nop
    IL_0007:  ret
  } // end of method TestRef::.ctor
}

.class public auto ansi beforefieldinit System.Runtime.InteropServices.UnmanagedType`1<T>
    extends [mscorlib]System.Object
{
    .method public hidebysig specialname rtspecialname 
        instance void .ctor () cil managed 
    {
        .maxstack 8

        IL_0000: ldarg.0
        IL_0001: call instance void [mscorlib]System.Object::.ctor()
        IL_0006: ret
    }
}
";

            var reference = CompileIL(ilSource, prependDefaultHeader: false);

            var code = @"
public class Test
{
    public static void Main()
    {
        var obj = new TestRef();

        obj.M1<int>();
    }
}";

            CreateCompilation(code, references: new[] { reference }).VerifyDiagnostics(
                );
        }

Other similar helpers should be checked for the same problem.