https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68093
Bug ID: 68093
Summary: [concepts] friend function declarations that differ
only by constraints are rejected as redefinitions
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tom at honermann dot net
Target Milestone: ---
I believe the following code is intended to be well-formed according to P0121r0
[1]. gcc trunk (r229299) currently rejects it.
$ cat t.cpp
struct S1 {};
struct S2 { using t1 = int; };
template<typename T>
concept bool Has_t1() {
return requires () { typename T::t1; };
}
template<typename T>
struct TS {
friend void f(TS) {}
friend void f(TS) requires Has_t1<T>() {} // Unexpected error: redefinition
};
TS<S1> ts1;
TS<S2> ts2;
auto x = []{
f(ts1);
f(ts2);
};
$ gcc --version
gcc (GCC) 6.0.0 20151025 (experimental)
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ gcc -c -std=c++1z t.cpp
t.cpp: In instantiation of ‘struct TS<S1>’:
t.cpp:12:8: required from here
t.cpp:10:17: error: redefinition of ‘void f(TS<S1>)’
friend void f(TS) requires Has_t1<T>() {} // Unexpected error:
redefinition
^
t.cpp:9:17: note: ‘void f(TS<S1>)’ previously defined here
friend void f(TS) {}
^
t.cpp: In instantiation of ‘struct TS<S2>’:
t.cpp:13:8: required from here
t.cpp:10:17: error: redefinition of ‘void f(TS<S2>)’
friend void f(TS) requires Has_t1<T>() {} // Unexpected error:
redefinition
^
t.cpp:9:17: note: ‘void f(TS<S2>)’ previously defined here
friend void f(TS) {}
^
[1]: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0121r0.pdf
