Ternary operator behaviour inconsistency [duplicate]

C# language specification, version 5, section 6.1.9:

An implicit constant expression conversion permits the following conversions:

• A constant-expression (§7.19) of type int can be converted to type sbyte, byte, short, ushort, uint, or ulong, provided the value of the constant-expression is within the range of the destination type.

Your first example is a constant expression, because it can be evaluated at compile time. But see section 7.19 for more details:

Only the following constructs are permitted in constant expressions:

• Literals (including the null literal).

[...]

• The predefined +, –, *, /, %, <<, >>, &, |, ^, &&, ||, ==, !=, <, >, <=, and >= binary operators, provided each operand is of a type listed above.
• The ?: conditional operator.

I believe in the first case the compiler knows that the strings are equal at compile time and therefore optimizes the code to just:

short d = 1;

That works because 1 can be assigned to short variable.

In the second case optimization cannot happen because compiler cannot infer equality at compile time, so it leaves:

short d = (DateTime.Now == DateTime.Now) ? (long)1 : (long)2;

This will compile:

short d = (DateTime.Now == DateTime.Now) ? (short)1 : (short)2;

IL (LinqPad) for call short d = ("obj" == "obj" ) ? 1 : 2;:

IL_0001:  ldc.i4.1    
IL_0002:  stloc.0     // d