This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 119a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
2025-12-20
[Accepted as a DR at the February, 2019 meeting.]
According to 13.7.5 [temp.friend] paragraph 8,
When a friend declaration refers to a specialization of a function template, the function parameter declarations shall not include default arguments, nor shall the inline specifier be used in such a declaration.
Presumably this should also include the constexpr specifier.
Notes from the December, 2018 teleconference:
This should also cover the newly-added consteval specifier.
Proposed resolution (February, 2019):
Change 13.7.5 [temp.friend] paragraph 8 as follows:
When a friend declaration refers to a specialization of a function template, the function parameter declarations shall not include default arguments, nor shall theinline specifierinline, constexpr, or consteval specifiers be used in such a declaration.