In which access control context are evaluated concepts?
This question is a follow up to this one
[temp.concept]/5 says:
A concept is not instantiated ([temp.spec]).
[ Note: An id-expression that denotes a concept specialization is evaluated as an expression ([expr.prim.id]). [...]]
So maybe an expression that name a concept specialization can have different value because of accessibility.
If it were the case, I wonder in which context would be evaluated the expression:
The context of the concept definition;
The context of the expression;
The context of the expression recursively applied to concepts expression appearing in concepts definition?
For example, what could be the value for A::b2 and A::b2_rec?
template<class T>
concept has_private = requires(){ &T::private_;};
template<class T>
concept has_private_rec = has_private<T>;
class B{
int private_;
friend class A;
};
inline constexpr bool b1 = has_private<B>;//I expects false
inline constexpr bool b1_rec = has_private_rec<B>;//I expects false
class A{
static constexpr bool b2 = has_private<B>; //?
static constexpr bool b2_rec = has_private_rec<B>; //?
};
Note Clang experimental concepts and gcc concepts TS implementation produce compilation error for b1 and b1_rec, but b2 and b2_rec are true;
c++ language-lawyer c++-concepts c++20
edited Nov 30 '18 at 16:11
TylerH
15.4k105067
asked Nov 12 '18 at 13:33
Oliv
8,3251956
add a comment |
This question is a follow up to this one
[temp.concept]/5 says:
A concept is not instantiated ([temp.spec]).
[ Note: An id-expression that denotes a concept specialization is evaluated as an expression ([expr.prim.id]). [...]]
So maybe an expression that name a concept specialization can have different value because of accessibility.
If it were the case, I wonder in which context would be evaluated the expression:
The context of the concept definition;
The context of the expression;
The context of the expression recursively applied to concepts expression appearing in concepts definition?
For example, what could be the value for A::b2 and A::b2_rec?
template<class T>
concept has_private = requires(){ &T::private_;};
template<class T>
concept has_private_rec = has_private<T>;
class B{
int private_;
friend class A;
};
inline constexpr bool b1 = has_private<B>;//I expects false
inline constexpr bool b1_rec = has_private_rec<B>;//I expects false
class A{
static constexpr bool b2 = has_private<B>; //?
static constexpr bool b2_rec = has_private_rec<B>; //?
};
Note Clang experimental concepts and gcc concepts TS implementation produce compilation error for b1 and b1_rec, but b2 and b2_rec are true;
c++ language-lawyer c++-concepts c++20
edited Nov 30 '18 at 16:11
TylerH
15.4k105067
asked Nov 12 '18 at 13:33
Oliv
8,3251956
I'm going to guess/hope thatb2isfalsebut honestly I do not know.
– Barry
Nov 12 '18 at 19:12
I’m tempted to bounty this, but fear it might bring well-meaning but poor answers.
– Jon Harper
Dec 10 '18 at 21:06
add a comment |
This question is a follow up to this one
[temp.concept]/5 says:
A concept is not instantiated ([temp.spec]).
[ Note: An id-expression that denotes a concept specialization is evaluated as an expression ([expr.prim.id]). [...]]
So maybe an expression that name a concept specialization can have different value because of accessibility.
If it were the case, I wonder in which context would be evaluated the expression:
The context of the concept definition;
The context of the expression;
The context of the expression recursively applied to concepts expression appearing in concepts definition?
For example, what could be the value for A::b2 and A::b2_rec?
template<class T>
concept has_private = requires(){ &T::private_;};
template<class T>
concept has_private_rec = has_private<T>;
class B{
int private_;
friend class A;
};
inline constexpr bool b1 = has_private<B>;//I expects false
inline constexpr bool b1_rec = has_private_rec<B>;//I expects false
class A{
static constexpr bool b2 = has_private<B>; //?
static constexpr bool b2_rec = has_private_rec<B>; //?
};
Note Clang experimental concepts and gcc concepts TS implementation produce compilation error for b1 and b1_rec, but b2 and b2_rec are true;
c++ language-lawyer c++-concepts c++20
edited Nov 30 '18 at 16:11
TylerH
15.4k105067
asked Nov 12 '18 at 13:33
Oliv
8,3251956
This question is a follow up to this one
[temp.concept]/5 says:
A concept is not instantiated ([temp.spec]).
[ Note: An id-expression that denotes a concept specialization is evaluated as an expression ([expr.prim.id]). [...]]
So maybe an expression that name a concept specialization can have different value because of accessibility.
If it were the case, I wonder in which context would be evaluated the expression:
The context of the concept definition;
The context of the expression;
The context of the expression recursively applied to concepts expression appearing in concepts definition?
For example, what could be the value for A::b2 and A::b2_rec?
template<class T>
concept has_private = requires(){ &T::private_;};
template<class T>
concept has_private_rec = has_private<T>;
class B{
int private_;
friend class A;
};
inline constexpr bool b1 = has_private<B>;//I expects false
inline constexpr bool b1_rec = has_private_rec<B>;//I expects false
class A{
static constexpr bool b2 = has_private<B>; //?
static constexpr bool b2_rec = has_private_rec<B>; //?
};
Note Clang experimental concepts and gcc concepts TS implementation produce compilation error for b1 and b1_rec, but b2 and b2_rec are true;
c++ language-lawyer c++-concepts c++20
c++ language-lawyer c++-concepts c++20
edited Nov 30 '18 at 16:11
TylerH
15.4k105067
asked Nov 12 '18 at 13:33
Oliv
8,3251956
edited Nov 30 '18 at 16:11
TylerH
15.4k105067
asked Nov 12 '18 at 13:33
Oliv
8,3251956
edited Nov 30 '18 at 16:11
TylerH
15.4k105067
edited Nov 30 '18 at 16:11
TylerH
15.4k105067
edited Nov 30 '18 at 16:11
TylerH
15.4k105067
15.4k105067
asked Nov 12 '18 at 13:33
Oliv
8,3251956
asked Nov 12 '18 at 13:33
Oliv
8,3251956
asked Nov 12 '18 at 13:33
Oliv
8,3251956
8,3251956
I'm going to guess/hope thatb2isfalsebut honestly I do not know.
– Barry
Nov 12 '18 at 19:12
I’m tempted to bounty this, but fear it might bring well-meaning but poor answers.
– Jon Harper
Dec 10 '18 at 21:06
add a comment |
I'm going to guess/hope thatb2isfalsebut honestly I do not know.
– Barry
Nov 12 '18 at 19:12
I’m tempted to bounty this, but fear it might bring well-meaning but poor answers.
– Jon Harper
Dec 10 '18 at 21:06
I'm going to guess/hope that
b2 is false but honestly I do not know.– Barry
Nov 12 '18 at 19:12
I'm going to guess/hope that
b2 is false but honestly I do not know.– Barry
Nov 12 '18 at 19:12
I’m tempted to bounty this, but fear it might bring well-meaning but poor answers.
– Jon Harper
Dec 10 '18 at 21:06
I’m tempted to bounty this, but fear it might bring well-meaning but poor answers.
– Jon Harper
Dec 10 '18 at 21:06
add a comment |
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I'm going to guess/hope that
b2isfalsebut honestly I do not know.– Barry
Nov 12 '18 at 19:12
I’m tempted to bounty this, but fear it might bring well-meaning but poor answers.
– Jon Harper
Dec 10 '18 at 21:06