# Saturday, 27 December 2003
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C# Shortcoming?
Tomas Restrepo posted some weird C# code on his weblog. It inspired me to test a few more corner cases:

namespace System {
   class Object { }
class ValueType { }


struct Int32 { }
class String { }
class A : string { public static void Main() { string s = new A(); } } }

If you compile this and then run peverify on the resulting executable, it will complain about every single type. Here is what's going on:

  • Object doesn't have a base class
  • ValueType extends our Object not the one in mscorlib
  • Int32 extends our ValueType
  • String extends our Object
  • A extends our String, but the local variable s is of type [mscorlib]System.String, so the assignment is not legal.

An obvious explanation for this (broken) behavior of the C# compiler is that Microsoft use the C# compiler to build mscorlib.dll. When compiling mscorlib.dll, the above behavior makes perfect sense. Of course, when you're not compiling mscorlib.dll, it doesn't make much sense and, in fact, it violates the language specification. For example, section 4.2.3 says:

       The keyword string is simply an alias for the predefined class System.String.

"predefined" being the important word here.

I guess it would be relatively easy to fix the compiler, but I think that there is actually an underlying problem: The C# language doesn't have support for assembly identities. Besides the above corner cases, this also causes problems in more real world situations.

Saturday, 27 December 2003 13:06:10 (W. Europe Standard Time, UTC+01:00)  #    Comments [0]