C++26 Pack-indexing have BUG

[Mq-b]

auto print(auto&&...args){
    [&]<std::size_t... idx>(std::index_sequence<idx...>){
        std::print("{} {} {} {}",args...[idx]...);
    }(std::make_index_sequence<sizeof...(args)>());
}

int main(){
    print(1,2,3,"🤣");
}

OK ! godbolt..

auto print(auto&&...args){
    [&]<std::size_t... idx>(std::index_sequence<idx...>){
        (std::print("{} ",args...[idx]), ...);
    }(std::make_index_sequence<sizeof...(args)>());
}

int main(){
    print(1,2,3,"🤣");
}

Error ! godbolt..

If changed to:

void print_one(auto& arg){
    std::print("{} ", arg);
}

void print(auto&&...args){
    [&]<std::size_t... idx>(std::index_sequence<idx...>){
        (::print_one<decltype((args...[idx]))>(args...[idx]), ...);
    }(std::make_index_sequence<sizeof...(args)>());
}

OK ! godbolt..

Seems to be moving out? But it doesn't matter. It's a BUG.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: mq白 (Mq-b)

```cpp auto print(auto&&...args){ [&]<std::size_t... idx>(std::index_sequence<idx...>){ std::print("{} {} {} {}",args...[idx]...); }(std::make_index_sequence<sizeof...(args)>()); }

int main(){
print(1,2,3,"🤣");
}

OK ! [godbolt..](https://godbolt.org/z/3KWWjb39T)

```cpp
auto print(auto&&...args){
    [&]<std::size_t... idx>(std::index_sequence<idx...>){
        (std::print("{} ",args...[idx]), ...);
    }(std::make_index_sequence<sizeof...(args)>());
}

int main(){
    print(1,2,3,"🤣");
}

Error ! godbolt..

If changed to:

void print_one(auto& arg){
    std::print("{} ", arg);
}

void print(auto&&...args){
    [&]<std::size_t... idx>(std::index_sequence<idx...>){
        (::print_one<decltype((args...[idx]))>(args...[idx]), ...);
    }(std::make_index_sequence<sizeof...(args)>());
}

OK ! godbolt..

Seems to be moving out? But it doesn't matter. It's a BUG.

[cor3ntin]

@Sirraide didn't you look at something very similar recently?

[Sirraide]

@Sirraide didn't you look at something very similar recently?

That was specifically about dependence of lambdas captures in lambdas with explicit object parameters that should have been dependent if the type of the explicit object parameter is.