IsAssignableTo on Enums

[AnakinRaW]

While reading ECMA 335 I noticed that in I.8.5.2

The CTS supports an enum [...] Instances of an enum, however, shall be assignable-to the underlying type, and
vice versa. That is, no cast (see §I.8.3.3) or coercion (see §I.8.3.2) is required to convert from the
enum to the underlying type [...]

However if i run
typeof(IntEnum).IsAssignableTo(typeof(int)) it gives me false as return. Also the CastingHelper::CanCastTo in src\coreclr\tools\common\typesystem return false.

Anybody can help me what I'm missing here.
Cheers

[sakno]

Because of strong typing: enum inherits from Enum class while Int32 inherits from ValueType. Moreover, some methods behave differently. For instance,

Console.WriteLine(EnvironmentVariableTarget.User.ToString());
Console.WriteLine(1.ToString());

The binary representations of both values are same, that's why cast or coercion is not needed. That is, at IL and machine code level there is no differences between them. However, event C# requires the cast because the cast changes the type. The type in OOP is not only the data encapsulated by the instance but also the behavior. That's why you need that cast. Just like Int32 and UInt32. Both contain 4-bytes long data, but behave differently.

IsAssignableTo checks whether the cast doesn't change the behavior. The only way to do this is to check upcast - casting from derived type to one of its base types.

[AnakinRaW]

Had to read that a couple of times, but it makes sense. Thanks :)!