Yes, your expression fatally confuses the JIT optimizer. The generated machine code looks like this:
if ((value == null || value == new string[0]) == false)
00000027 test esi,esi ; value == null?
00000029 je 00000075
0000002b xor edx,edx ; new string[0]
0000002d mov ecx,6D913BD2h
00000032 call FFD20BC8
00000037 cmp eax,esi ; (value == new string[0]) == false?
00000039 je 00000075
{
Console.WriteLine("Post-check Value is: " + value);
0000003b mov ecx,dword ptr ds:[03532090h] ; "Post-check value is: "
00000041 xor edx,edx ; BUGBUG not null!
00000043 call 6D70B7E8 ; String.Concat()
00000048 mov esi,eax ;
0000004a call 6D72BE08 ; get Console.Out
0000004f mov ecx,eax
00000051 mov edx,esi
00000053 mov eax,dword ptr [ecx]
00000055 call dword ptr [eax+000000D8h] ; Console.WriteLine()
The bug occurs at address 41, the optimizer has concluded that value will always be null so it directly passes a null to String.Concat().
For comparison, this is the code that’s generated when JIT optimization is turned off:
Console.WriteLine("Post-check Value is: " + value);
00000056 mov ecx,dword ptr ds:[03342090h]
0000005c mov edx,dword ptr [ebp-8]
0000005f call 6D77B790
The code got moved, but do note that at address 5c it now uses the local variable (value) instead of null.
You can report this bug at connect.microsoft.com. The workaround is simple:
if (value != null)
{
Console.WriteLine("Post-check Value is: " + value);
new PrintManager().Print("blah", value);
}