Unexpected warning for pack indexing

[breese]

Suppose we use the feature test macro to only use pack indexing when available

template <std::size_t N, typename... Args>
constexpr auto my_element(Args... args) {
#if __cpp_pack_indexing >=  202311L
  return args...[N];
#else
  // Do something else
#endif
}

A compiler warning is emitted when compiling for C++23 or earlier

<source>:13:16: warning: pack indexing is a C++2c extension [-Wc++26-extensions]
   13 |         return args...[N];
      |                ^
1 warning generated.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Bjørn Reese (breese)

Suppose we use the feature test macro to only use pack indexing when available ``` template <std::size_t N, typename... Args> constexpr auto my_element(Args... args) { #if __cpp_pack_indexing >= 202311L return args...[N]; #else // Do something else #endif } ``` A compiler warning is emitted when compiling for C++23 or earlier ``` <source>:13:16: warning: pack indexing is a C++2c extension [-Wc++26-extensions] 13 | return args...[N]; | ^ 1 warning generated. ```

[zwuis]

Similar issue: #109311.

[cor3ntin]

right, the feature test macro is set in all language modes because the feature is supported as an extension in all language modes