C++23 Ranges Pipe Operator Not Recognized by IntelliSense

[marpaia]

Environment

• VS Code Version: 1.93.1
• C/C++ Extension Version: v1.22.11
• OS: macOS
• Compiler: Clang (Apple)
• C++ Standard: C++23
• Standard Library: libc++

Bug Summary and Steps to Reproduce

Bug Summary

IntelliSense incorrectly reports errors for valid C++23 ranges pipe operator syntax in a modern C++ project. The project is a single CMake project using C++23 with libc++ and Clang. The error occurs in any source file that uses the ranges pipe operator, despite the code compiling and running correctly.

Steps to Reproduce

1. Create a new C++ project using CMake

2. Configure the project to use C++23 with libc++ and Clang

3. Add the following configuration to .vscode/c_cpp_properties.json:

   {
       "configurations": [
           {
               "name": "Mac",
               "compilerPath": "/usr/bin/clang++",
               "includePath": [
                   "${workspaceFolder}/**",
                   "${workspaceFolder}/build/**",
                   "/opt/homebrew/include",
                   "/opt/homebrew/opt/libomp/include"
               ],
               "defines": [
                   "_LIBCPP_ENABLE_EXPERIMENTAL",
                   "_LIBCPP_STD_VER=23"
               ],
               "cStandard": "c23",
               "cppStandard": "c++23",
               "intelliSenseMode": "clang-arm64",
               "compilerArgs": [
                   "-fexperimental-library",
                   "-stdlib=libc++",
                   "-std=c++23"
               ]
           }
       ]
   }

4. Create a new .cpp file with the following code:

   auto longFlag =
       flags | std::views::filter([](std::string_view f) { return f.starts_with("--"); }) | std::views::take(1);

Expected behavior:

• IntelliSense should recognize the ranges pipe operator as valid C++23 syntax
• No error squiggles should appear

Actual behavior:

• IntelliSense shows error: "no operator '|' matches these operands" (error 349)
• Code compiles and runs correctly with Clang

Error Details

IntelliSense error message:

    no operator "|" matches these operands
    operand types are: std::__1::ranges::drop_while_view<std::__1::basic_string_view<char, std::__1::char_traits<char>>, int (*)(int _c)> | const std::__1::ranges::views::__reverse::__fn

The code compiles and runs correctly with Clang, suggesting this is an IntelliSense limitation with C++23 ranges features.

Configuration and Logs

My c_cpp_properties.json:


    {
        "configurations": [
            {
                "name": "Mac",
                "compilerPath": "/usr/bin/clang++",
                "includePath": [
                    "${workspaceFolder}/**",
                    "${workspaceFolder}/build/**",
                    "/opt/homebrew/include",
                    "/opt/homebrew/opt/libomp/include"
                ],
                "defines": [
                    "_LIBCPP_ENABLE_EXPERIMENTAL",
                    "_LIBCPP_STD_VER=23"
                ],
                "cStandard": "c23",
                "cppStandard": "c++23",
                "intelliSenseMode": "clang-arm64",
                "compilerArgs": [
                    "-fexperimental-library",
                    "-stdlib=libc++",
                    "-std=c++23"
                ]
            }
        ]
    }


C/C++: Log Diagnostics:


-------- Diagnostics - 1/7/2025, 1:51:13 PM
Version: 1.22.11
Current Configuration:
{
    "name": "Mac",
    "compilerPath": "/usr/bin/clang++",
    "includePath": [
        "/Users/marpaia/git/cimlr/cimlr/**",
        "/Users/marpaia/git/cimlr/cimlr/build/**",
        "/opt/homebrew/include",
        "/opt/homebrew/opt/libomp/include"
    ],
    "defines": [
        "_LIBCPP_ENABLE_EXPERIMENTAL",
        "_LIBCPP_STD_VER=23"
    ],
    "macFrameworkPath": [
        "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks"
    ],
    "cStandard": "c23",
    "cppStandard": "c++23",
    "intelliSenseMode": "clang-arm64",
    "compilerArgs": [
        "-fexperimental-library",
        "-stdlib=libc++",
        "-std=c++23"
    ],
    "compilerPathIsExplicit": true,
    "cStandardIsExplicit": true,
    "cppStandardIsExplicit": true,
    "intelliSenseModeIsExplicit": true,
    "compilerPathInCppPropertiesJson": "/usr/bin/clang++",
    "mergeConfigurations": false,
    "browse": {
        "path": [
            "/Users/marpaia/git/cimlr/cimlr/**",
            "/Users/marpaia/git/cimlr/cimlr/build/**",
            "/opt/homebrew/include",
            "/opt/homebrew/opt/libomp/include",
            "${workspaceFolder}"
        ],
        "limitSymbolsToIncludedHeaders": true
    }
}
Modified Settings:
{
    "C_Cpp.formatting": "clangFormat"
}
Additional Tracked Settings:
{
    "editorTabSize": 4,
    "editorInsertSpaces": true,
    "editorAutoClosingBrackets": "languageDefined",
    "filesEncoding": "utf8",
    "filesAssociations": {
        "*.h.in": "cpp",
        "*.cmake.in": "cmake"
    },
    "filesExclude": {
        "**/.git": true,
        "**/.svn": true,
        "**/.hg": true,
        "**/CVS": true,
        "**/.DS_Store": true,
        "**/Thumbs.db": true
    },
    "filesAutoSaveAfterDelay": false,
    "editorInlayHintsEnabled": true,
    "editorParameterHintsEnabled": true,
    "searchExclude": {
        "**/node_modules": true,
        "**/bower_components": true,
        "**/*.code-search": true
    },
    "workbenchSettingsEditor": "ui"
}
cpptools version (native): 1.22.11.0
Current database path: /Users/marpaia/Library/Caches/vscode-cpptools/527954c535fb49717f7dab8f4b3b48c9/.browse.VC.db
Translation Unit Mappings:
[ /Users/marpaia/git/cimlr/cimlr/cimlr/cli/CommandLine.cpp - source TU]:
Translation Unit Configurations:
[ /Users/marpaia/git/cimlr/cimlr/cimlr/cli/CommandLine.cpp ]
    Process ID: 51969
    Memory Usage: 541 MB
    Compiler Path: /usr/bin/clang++
    Includes:
        /opt/homebrew/include
        /opt/homebrew/Cellar/libomp/19.1.6/include
        /Users/marpaia/git/cimlr/cimlr
    System Includes:
        /Library/Developer/CommandLineTools/SDKs/MacOSX15.2.sdk/usr/include/c++/v1
        /Library/Developer/CommandLineTools/usr/lib/clang/16/include
        /Library/Developer/CommandLineTools/SDKs/MacOSX15.2.sdk/usr/include
        /Library/Developer/CommandLineTools/usr/include
    Frameworks:
        /Library/Developer/CommandLineTools/SDKs/MacOSX15.2.sdk/System/Library/Frameworks
    Defines:
        _LIBCPP_ENABLE_EXPERIMENTAL
        _LIBCPP_STD_VER=23
        __has_feature(experimental_library)=1
    Standard Version: c++23
    IntelliSense Mode: macos-clang-arm64
    Other Flags:
        --clang
        --clang_version=170006
Total Memory Usage: 541 MB

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 14024
Number of files parsed: 2141

Other Extensions

No response

Additional context

IntelliSense error message:

    no operator "|" matches these operands
    operand types are: std::__1::ranges::drop_while_view<std::__1::basic_string_view<char, std::__1::char_traits<char>>, int (*)(int _c)> | const std::__1::ranges::views::__reverse::__fn

The code compiles and runs correctly with Clang, suggesting this is an IntelliSense limitation with C++23 ranges features.

[sean-mcmanus]

@marpaia What is the type of flags in your code sample? I'm assuming std::string_view...umm, but that doesn't seem to compile.

[marpaia]

Hey @sean-mcmanus, thanks for taking a look at this. It is indeed a std::string_view. Here is the whole function:

std::vector<std::string> CommandLine::splitFlags(const std::string_view flags) {
  std::vector<std::string> result;

  for (const auto flag : flags | std::views::split(',')) {
    std::string_view flagView(flag.begin(), flag.end());
    auto trimmed = flagView | std::views::drop_while(isspace) | std::views::reverse | std::views::drop_while(isspace) |
                   std::views::reverse;

    if (!trimmed.empty()) {
      result.emplace_back(trimmed.begin(), trimmed.end());
    }
  }
  return result;
}

This is the header for reference:

  /**
   * @brief Splits a comma-separated flag list into individual flags
   *
   * Handles whitespace trimming and empty segments.
   *
   * @param flags Comma-separated flag list
   * @return Vector of individual flags
   */
  [[nodiscard]] static std::vector<std::string> splitFlags(std::string_view flags);

Let me know if you want me to provide the whole header and implementation file and/or any of the rest of my build configurations.