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CWG3166 [expr.reflect] Clarify whether the protected access rule for a pointer-to-member applies to a reflect-expression #852
Description
Full name of submitter: Aurelien Cassagnes
Issue description: It is not clear whether the following is valid:
class A {
protected:
void f();
};
struct B : A {
static constexpr auto r = ^^A::f;
};
According to [expr.reflect]/7.2, "overload resolution for the expression" &A::f "with no target shall select a unique function". Do the restrictions in [class.protected] on the use of the expression &A::f apply to the reflect-expression?
Suggested resolution (by Brian): Edit [expr.reflect]/7.2 as follows:
Otherwise, if the id-expression denotes an overload set
S,overload resolution for the expression &S with no target shall select a unique function ([over.over])the expression&id-expression shall be well-formed when considered as an unevaluated operand; R representsthatthe function selected by overload resolution ([over.over]).
Activity
jensmaurer commentedon Mar 11, 2026
CWG3166
[-][expr.reflect] Clarify whether the protected access rule for a pointer-to-member applies to a reflect-expression[/-][+]CWG3166 [expr.reflect] Clarify whether the protected access rule for a pointer-to-member applies to a reflect-expression[/+]timsong-cpp commentedon Mar 11, 2026
Does that wording block taking a reflection of a deleted function?
t3nsor commentedon Mar 11, 2026
Yeah, I guess it does. I forgot that we had a special rule to support that.
t3nsor commentedon May 12, 2026
Following up on the discussion from the most recent telecon.
We should change [expr.reflect]/7.2 to avoid referring to overload resolution, because the process of resolving the "address of an overload set" as specified in [over.over] is, technically, not a form of overload resolution. See [over.match.general].
Originally, I thought the choice was between changing [expr.reflect] and [class.protected]. But the former needs changes no matter what wording strategy we choose, so I continue to think that we shouldn't edit [class.protected]. We should just make it clear that the deletedness check doesn't apply. Here's the updated edit for [expr.reflect]/7.2:
jensmaurer commentedon May 14, 2026
Updated: CWG3166