Uh, why? A cv-qualified class type is still a class type. For example, this works:

struct B {};
using CB = const B;
struct D : CB { };

But this doesn't work (at least clang, GCC and VS reject the code), as there is no way for the compiler to parse the const below, given the C++ grammar.

struct B{};
struct D : const B {};

So, I presume that your snippet compiles because the CB in struct D : CB {} doesn't carry the const anymore. Although I still need to take a look into this in the Standard.

No, it compiles because of [class.derived] p2, and it would stop working with your change.

In other words, "any cv-qualifiers are ignored" in [class.derived] p2 is what causes "doesn't carry the const anymore" to be true, so don't try to remove those words!

@jwakely

Could you tell me which grammar production would allow the compiler to parse the const in struct D : const B{}; above?

@jwakely I can see what you mean now.

I meant Jens's snippet when I said "it compiles", because that's the one that compiles. Yours doesn't compile.

In his example, the class-or-decltype CB denotes a const-qualified class type. When used as a base class, any cv-qualifiers are ignored, so the base class is B. That's what [class.derived] p2 means. Changing [class.derived] p2 would break the example, and so is not only non-editorial, but completely wrong.

What part of this is confusing you?

As I said before I have already understood your point. But to avoid misunderstandings about this paragraph I would surely insert the Note below, as follows:

A class-or-decltype shall denote a (possibly cv-qualified) class type that is not an incompletely defined
class (11.4); any cv-qualifiers are ignored. [Note: the code below compiles

struct B {};
using CB = const B;
struct D : CB { };

-end note] The class denoted by ...

Since "struct D: const B" is syntactically invalid, this is the only remaining choice, with no need for further elaboration. The standard is not a tutorial.