c++ - Nested enum and nested class have different behavior -

consider these 2 examples:

struct x {     class e { static const int z = 16 };     static const int b = x::z;   // x has no member z };  struct y  {     enum e { z = 16 };     static const int b = y::z;   // ok }; 

is there section of standard explains behavior?

yes, there such sections in c++ standard.

the first 1 is

9.9 nested type names

1 type names obey same scope rules other names. in particular, type names defined within class definition cannot used outside class without qualification.

it more precisely cite following quote

2 name of class member shall used follows: — in scope of class (as described above) or class derived (clause 10) class, — after . operator applied expression of type of class (5.2.5) or class derived class, — after -> operator applied pointer object of class (5.2.5) or class derived class, — after :: scope resolution operator (5.1) applied name of class or class derived class.

and second 1 is

11.7 nested classes

1 nested class member , such has same access rights other member. members of enclosing class have no special access members of nested class; the usual access rules (clause 11) shall obeyed.

in definition if not take account typo (the absence of semicolon after definition of z)

struct x {     class e { static const int z = 16 };     static const int b = x::z;   // x has no member z }; 

you trying access z 1) without qualification , 2) has private access control.

the correct definition as

struct x {     class e { public: static const int z = 16; };     static const int b = e::z; }; 

as enumeration enumerators of unscopped enumeration members of class enumeration defined.

9.2 class members

1 member-specification in class definition declares full set of members of class; no member can added elsewhere. members of class data members, member functions (9.3), nested types, , enumerators.