https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104606
Bug ID: 104606
Summary: Regression in comparison operator resolution with
std::optional
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: julien.philippon at epitech dot eu
Target Milestone: ---
Created attachment 52480
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52480&action=edit
Preprocessed file trigering the regression
This code used to compile with G++ 11.1 but does not anymore with G++ 11.2 :
```
#include <optional>
#include <variant>
#include <vector>
struct Value : public std::variant<int, std::vector<Value>> {
using variant::variant;
};
struct Comparator {
template <typename T>
bool operator<=(const T &rhs)
{
return true;
}
};
int main()
{
auto test = Comparator() <= Value{1};
auto test2 = Comparator() <= std::make_optional(Value{1});
}
```
In GCC 11.1 the comparison correctly deduced in the two cases that the lower or
equal operator of Comparator should be used, but in GCC 11.2, the second
comparison which involve an optional fails to compile.
It looks like GCC is trying to instantiate the three-way comparison operator of
Value, instead of using the operator of Comparator.
Output from g++ -v :
```
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/11.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --with-isl
--with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit
--enable-cet=auto --enable-checking=release --enable-clocale=gnu
--enable-default-pie --enable-default-ssp --enable-gnu-indirect-function
--enable-gnu-unique-object --enable-linker-build-id --enable-lto
--enable-multilib --enable-pgo-build=lto --enable-plugin --enable-shared
--enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-werror --with-build-config=bootstrap-lto
--enable-link-serialization=1 gdc_include_dir=/usr/include/dlang/gdc
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.2.0 (GCC)
```
