Rationale (from Bjarne Stroustrup's ["C++11 FAQ"](http://www.stroustrup.com/C++11FAQ.html#enum)):

>
> The enum classes ("new enums", "strong enums") address three problems with traditional C++ enumerations:
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> * conventional enums implicitly convert to int, causing errors when someone does not want an enumeration to act as an integer.
> * conventional enums export their enumerators to the surrounding scope, causing name clashes.
> * the underlying type of an enum cannot be specified, causing confusion, compatibility problems, and makes forward declaration impossible.
>
> The new enums are "enum class" because they combine aspects of traditional enumerations (names values) with aspects of classes (scoped members and absence of conversions).