https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108570
Bug ID: 108570
Summary: [concept] GCC tries to instantiate additional unneeded
operator.
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: fsb4000 at yandex dot ru
Target Milestone: ---
Hello!
Look at the code:
```c++
template <class T>
concept Foo = requires(T val) {
val == val;
};
template <class T>
struct Bar {};
template <class T>
bool operator==(const Bar<T>&, const Bar<T>&);
template <class T>
requires Foo<Bar<T>>
bool operator==(const Bar<T>&, int);
static_assert(Foo<Bar<int>>);
```
$ g++ -std=c++20 test.cpp
test.cpp: In substitution of 'template<class T> requires Foo<Bar<T> > bool
operator==(const Bar<T>&, int) [with T = int]':
test.cpp:3:7: required from here
test.cpp:2:9: required for the satisfaction of 'Foo<Bar<T> >' [with T = int]
test.cpp:2:15: in requirements with 'T val' [with T = Bar<int>]
test.cpp:2:15: error: satisfaction of atomic constraint 'requires(T val) {val
== val;} [with T = Bar<int>]' depends on itself
2 | concept Foo = requires(T val) {
| ^~~~~~~~~~~~~~~~~
3 | val == val;
| ~~~~~~~~~~~
4 | };
| ~
test.cpp: In substitution of 'template<class T> requires Foo<Bar<T> > bool
operator==(const Bar<T>&, int) [with T = int]':
test.cpp:3:7: required from here
test.cpp:2:9: required for the satisfaction of 'Foo<Bar<T> >' [with T = int]
test.cpp:2:15: in requirements with 'T val' [with T = Bar<int>]
test.cpp:2:15: error: satisfaction of atomic constraint 'requires(T val) {val
== val;} [with T = Bar<int>]' depends on itself
$ g++ -v
Using built-in specs.
COLLECT_GCC=C:\tools\msys64\mingw64\bin\g++.exe
COLLECT_LTO_WRAPPER=C:/tools/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/lto-wrapper.exe
Target: x86_64-w64-mingw32
Configured with: ../gcc-12.2.0/configure --prefix=/mingw64
--with-local-prefix=/mingw64/local --build=x86_64-w64-mingw32
--host=x86_64-w64-mingw32 --target=x86_64-w64-mingw32
--with-native-system-header-dir=/mingw64/include --libexecdir=/mingw64/lib
--enable-bootstrap --enable-checking=release --with-arch=x86-64
--with-tune=generic --enable-languages=c,lto,c++,fortran,ada,objc,obj-c++,jit
--enable-shared --enable-static --enable-libatomic --enable-threads=posix
--enable-graphite --enable-fully-dynamic-string
--enable-libstdcxx-filesystem-ts --enable-libstdcxx-time
--disable-libstdcxx-pch --enable-lto --enable-libgomp --disable-multilib
--disable-rpath --disable-win32-registry --disable-nls --disable-werror
--disable-symvers --with-libiconv --with-system-zlib --with-gmp=/mingw64
--with-mpfr=/mingw64 --with-mpc=/mingw64 --with-isl=/mingw64
--with-pkgversion='Rev1, Built by MSYS2 project'
--with-bugurl=https://github.com/msys2/MINGW-packages/issues --with-gnu-as
--with-gnu-ld --disable-libstdcxx-debug --with-boot-ldflags=-static-libstdc++
--with-stage1-ldflags=-static-libstdc++
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.2.0 (Rev1, Built by MSYS2 project
MSVC and clang++ can compile the code.
Do you think this is GCC bug or MSVC and clang++ are too permissive?
Found by hui.xie1...@gmail.com and varco...@apple.com while implementing
zip_iterator
Godbolt link: https://godbolt.org/z/ff41PE9KG
