nguerrera

class X { }

class Foo {
    public virtual X Y { get; set; }
    public virtual X Z { get; set; }
}

class Bar : Foo {
    public override X Y { set { } }
    public override X Z { get { return null; } }

nguerrera

/*
  "dependencies": {
        "System.Console": "4.0.0-beta-23516",
        "System.IO.FileSystem": "4.0.1-beta-23516",
        "System.Reflection": "4.1.0-beta-23516",
        "System.Reflection.Metadata": "1.1.0",
        "System.Reflection.TypeExtensions": "4.1.0-beta-23516"
      }
*/

nguerrera

II.23.2.12 Type 

Type ::=    
BOOLEAN | CHAR | I1 | U1 | I2 | U2 | I4 | U4 | I8 | U8 | R4 | R8 | I | U 
| ARRAY ModifiableType ArrayShape (general array, see §II.23.2.13) 
| CLASS TypeDefOrRefOrSpecEncoded 
| FNPTR MethodDefSig 
| FNPTR MethodRefSig 
| GENERICINST (CLASS | VALUETYPE) TypeDefOrRefOrSpecEncoded GenArgCount ModifiableType* 
| MVAR number 

nguerrera

/*
The absence of the C# unsafe keyword and switch does not guarantee code
is type or memory safe. It merely prevents the use of pointer types and
fixed size buffers.

The only thing that can guarantee type and memory safety is
verification and CAS/transparency enforcement.

In particular, the absence of unsafe C# blocks does NOT:

nguerrera

@davkean's thoughts on "contract breaking" exceptions:

You do not want to derive from InvalidOperationException. It and ArgumentException (and derivatives) are considered "contract breaking" exceptions.

Contract breaking exceptions should only be thrown to indicate that the caller has a bug. I pretend that every time I go to throw these exceptions that the process will be torn down immediately. If I’m okay with that, then I throw it, if not, then I should be throwing a

nguerrera

using System;
 
static class Program 
{
    static bool A()
    { 
        return false;
    }
    
    static int А()

nguerrera

// And this program can be writen in C# after all if you use an extension method! 
// (And the codegen is exactly as the optimal hand-written IL below.)
//
// Thanks to Vladimir Sadov on the compiler team for teaching me about it!

static class Program
{
    static void Main()
    {
        var f = new Func<string>("World".StaticMethod);