https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115708
Bug ID: 115708
Summary: gcc fails to identify valid friend function
declaration with deduced return type
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: rush102333 at gmail dot com
Target Milestone: ---
Please consider the following code:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
struct Base {
auto f(int) { return 1; }
};
struct A : Base {
friend auto Base::f(int) ;
};
int main() {
A instance;
auto ptr_1=&A::f;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GCC-13.2 rejects this by complaining that there's no matched function for the
friend declaration of "auto Base::f(int)":
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:6:17: error: no declaration matches 'auto Base::f(int)'
6 | friend auto Base::f(int) ;
| ^~~~
<source>:2:10: note: candidate is: 'auto Base::f(int)'
2 | auto f(int) { return 1; }
| ^
<source>:1:8: note: 'struct Base' defined here
1 | struct Base {
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
That's unusual because the code is apparently valid. Changing the return type
of "f" from "auto" to "int" can make the code compile.
Clang also accepts this code. Please check https://godbolt.org/z/z8PYK17n8
