[BUG] Code Example Doesn't Compile

[codereport]

The following code example doesn't compile:

CppInsights Link: https://cppinsights.io/s/9b7c139b

The equivalent code on Godbolt does. I am not sure what is causing the issue but seems like it should work. Here is a twitter link with some discussion as well: https://twitter.com/code_report/status/1646638445555761152?s=20

[andreasfertig]

Hello @codereport,

thanks for raising this issue. The short answer is that C++ Insights still uses Clang 15, which does not support ranges (at least to my knowledge). I created an issue for the Clang update, #525.

The longer answer is it's more complicated.

In the link you provided, Clang is used with libstdc++ (from GCC) because that's the default under Linux. You can switch the lib under "More Transformation" (maybe not the best heading). Once C++ Insights uses Clang 16, that would work. I don't know why Clang doesn't seem to play well with libstdc++ regarding ranges.

Even with Clang 16, I believe you will not see what you are looking for because C++ Insights does only expand statements from the current source file. #428 provides an explanation. I can still imagine supporting this, but I assume that the resulting code could be a lot to process. I used an experimental version and... well... a lot of code was produced.

The following is the transformation result from my local C++ Insights version using Clang 16 (without the additional patch to dive into headers):

include <vector>
#include <ranges>

std::ranges::transform_view<std::ranges::ref_view<std::vector<int, std::allocator<int> > >, __lambda_7_40> plus_one(std::vector<int, std::allocator<int> > && vec)
{

  class __lambda_7_40
  {
    public:
    template<class type_parameter_0_0>
    inline /*constexpr */ auto operator()(type_parameter_0_0 e) const
    {
      return e + 1;
    }

    #ifdef INSIGHTS_USE_TEMPLATE
    template<>
    inline /*constexpr */ int operator()<int>(int e) const
    {
      return e + 1;
    }
    #endif

    private:
    template<class type_parameter_0_0>
    static inline /*constexpr */ auto __invoke(type_parameter_0_0 e)
    {
      return __lambda_7_40{}.operator()<type_parameter_0_0>(e);
    }
    public:
    // inline /*constexpr */ __lambda_7_40() noexcept = default;
    // inline /*constexpr */ __lambda_7_40(__lambda_7_40 &&) noexcept = default;
    // /*constexpr */ __lambda_7_40() = default;

  } __lambda_7_40{};

  return operator|(vec, std::ranges::views::transform.operator()(__lambda_7_40));
}


int main()
{
  plus_one(std::vector<int, std::allocator<int> >{std::initializer_list<int>{1, 2, 3}});
  return 0;
}

Andreas

[andreasfertig]

Fixed by #569.