Weird interaction with C++20's abbreviated function template #7446

sam20908 · 2021-04-30T18:17:41Z

Bug type: Language Service

Describe the bug

OS and Version: Windows 10
VS Code Version: 1.55.2
C/C++ Extension Version: 1.3.1
Other extensions you installed (and if the issue persists after disabling them):
If using SSH remote, specify OS of remote machine:
A clear and concise description of what the bug is, including information about the workspace (i.e. is the workspace a single project or multiple projects, size of the project, etc).

The language service compiler EDG fails to compile a valid C++20 code when using abbreviated function templates.

There are precisely two problems here: the two occurrences of abbreviated function template parameters

constexpr bind_back_wrap(const Fn &fn, auto &&...args)

and

constexpr auto operator()(auto &&...args)

They cause problems for EDG, but compiles fine with MSVC with C++20 (I used cl /c /MD /std:c++latest main.cpp)

EDG successfully compiles when you replace the occurrences with:

template <typename... Args>
constexpr bind_back_wrap(const Fn &fn, Args &&...args) : fn(fn), back_args{std::forward<Args>(args)...} {}

and

template <typename... Args>
constexpr auto operator()(Args &&...args) const
{
	return std::apply(fn, std::tuple_cat(std::forward_as_tuple(std::forward<Args>(args)...), back_args));
}

Sorry if this repro is a little complex, as I couldn't repro the issue any other way.

Steps to reproduce

Create a main.cpp
Paste the following code:

#include <utility>
#include <functional>
#include <tuple>

template <typename Fn, typename... BackArgs>
struct bind_back_wrap
{
	const Fn &fn;
	std::tuple<BackArgs...> back_args;

	constexpr bind_back_wrap(const Fn &fn, auto &&...args) : fn(fn),
															 back_args{std::forward<decltype(args)>(args)...} {}

	constexpr auto operator()(auto &&...args) const
	{
		return std::apply(fn, std::tuple_cat(std::forward_as_tuple(std::forward<decltype(args)>(args)...), back_args));
	}
};

template <typename Fn, typename... Args>
constexpr auto bind_back(const Fn &fn, Args &&...args)
{
	return bind_back_wrap<Fn, Args...>(fn, std::forward<Args>(args)...);
}

inline constexpr auto add = [](const auto &a, const auto &b) { return a + b; };

int main()
{
	auto foo = bind_back(add, 2);
	foo(1);
}

See error (or compile with cl /BE /c /MD /std:c++latest main.cpp)

Expected behavior

Code should compile fine and no errors

Code sample and logs

Code sample
Configurations in c_cpp_properties.json

{
    "configurations": [
        {
            "name": "Win32",
            "includePath": [
                "${workspaceFolder}/**"
            ],
            "defines": [
                "_DEBUG",
                "UNICODE",
                "_UNICODE"
            ],
            "windowsSdkVersion": "10.0.19041.0",
            "compilerPath": "C:/Program Files (x86)/Microsoft Visual Studio/2019/Preview/VC/Tools/MSVC/14.29.30031/bin/Hostx64/x64/cl.exe",
            "cStandard": "c17",
            "cppStandard": "c++20",
            "intelliSenseMode": "windows-msvc-x64",
            "configurationProvider": "ms-vscode.cmake-tools"
        }
    ],
    "version": 4
}

Logs from running C/C++: Log Diagnostics from the VS Code command palette

-------- Diagnostics - 2021-04-30, 11:15:59 a.m.
Version: 1.3.1
Current Configuration:
{
    "name": "Win32",
    "includePath": [
        "${workspaceFolder}/**"
    ],
    "defines": [
        "_DEBUG",
        "UNICODE",
        "_UNICODE"
    ],
    "windowsSdkVersion": "10.0.19041.0",
    "compilerPath": "C:/Program Files (x86)/Microsoft Visual Studio/2019/Preview/VC/Tools/MSVC/14.29.30031/bin/Hostx64/x64/cl.exe",
    "cStandard": "c17",
    "cppStandard": "c++20",
    "intelliSenseMode": "windows-msvc-x64",
    "configurationProvider": "ms-vscode.cmake-tools",
    "compilerArgs": [],
    "intelliSenseModeIsExplicit": true,
    "cStandardIsExplicit": true,
    "cppStandardIsExplicit": true,
    "compilerPathIsExplicit": true,
    "browse": {
        "path": [
            "${workspaceFolder}/**"
        ],
        "limitSymbolsToIncludedHeaders": true
    }
}
Translation Unit Mappings:
[ C:\Users\Sam Huang\Projects\cpptools-repro-sandbox\main.cpp ]:
    C:\USERS\SAM HUANG\PROJECTS\CPPTOOLS-REPRO-SANDBOX\MAIN.CPP
Translation Unit Configurations:
[ C:\Users\Sam Huang\Projects\cpptools-repro-sandbox\main.cpp ]:
    Process ID: 3964
    Memory Usage: 34 MB
    Compiler Path: C:/Program Files (x86)/Microsoft Visual Studio/2019/Preview/VC/Tools/MSVC/14.29.30031/bin/Hostx64/x64/cl.exe
    Includes:
        C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\2019\PREVIEW\VC\TOOLS\MSVC\14.29.30031\INCLUDE
        C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\UM
        C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\UCRT
        C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\SHARED
        C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\WINRT
        C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\CPPWINRT
    Defines:
        _DEBUG
        UNICODE
        _UNICODE
    Standard Version: ms_c++latest
    IntelliSense Mode: windows-msvc-x64
Total Memory Usage: 34 MB

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 4809

Logs from the language server logging

cpptools/didChangeCppProperties
MSVC intelliSenseMode specified.  Configuring for compiler cl.exe.
Code browsing service initialized
MSVC intelliSenseMode specified.  Configuring for compiler cl.exe.
  Folder: C:/PROGRAM FILES (X86)/MICROSOFT VISUAL STUDIO/2019/PREVIEW/VC/TOOLS/MSVC/14.29.30031/INCLUDE/* will be indexed
  Folder: C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/CPPWINRT/ will be indexed
  Folder: C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/SHARED/ will be indexed
  Folder: C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/UCRT/ will be indexed
  Folder: C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/UM/ will be indexed
  Folder: C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/WINRT/ will be indexed
  Folder: C:/USERS/SAM HUANG/PROJECTS/CPPTOOLS-REPRO-SANDBOX/ will be indexed
cpptools/clearCustomConfigurations
Populate include completion cache.
Discovering files...
  Processing folder (non-recursive): C:/PROGRAM FILES (X86)/MICROSOFT VISUAL STUDIO/2019/PREVIEW/VC/TOOLS/MSVC/14.29.30031/INCLUDE
  Processing folder (recursive): C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/CPPWINRT/
  Processing folder (recursive): C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/SHARED/
  Processing folder (recursive): C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/UCRT/
  Processing folder (recursive): C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/UM/
  Processing folder (recursive): C:/PROGRAM FILES (X86)/WINDOWS KITS/10/INCLUDE/10.0.19041.0/WINRT/
  Processing folder (recursive): C:/USERS/SAM HUANG/PROJECTS/CPPTOOLS-REPRO-SANDBOX/
  Discovering files: 4810 file(s) processed
  1 file(s) removed from database
Done discovering files.
Parsing remaining files...
  Parsing: 0 files(s) processed
Done parsing remaining files.
cpptools/getCodeActions: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 2)
textDocument/didOpen: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp
cpptools/activeDocumentChange: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp
cpptools/textEditorSelectionChange
cpptools/getDocumentSymbols: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 3)
cpptools/textEditorSelectionChange
cpptools/getSemanticTokens: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 4)
cpptools/getDocumentSymbols
  tag parsing file: C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\2019\PREVIEW\VC\TOOLS\MSVC\14.29.30031\INCLUDE\CODEANALYSIS\SOURCEANNOTATIONS.H
idle loop: reparsing the active document
Checking for syntax errors: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp
sending compilation args for C:\USERS\SAM HUANG\PROJECTS\CPPTOOLS-REPRO-SANDBOX\MAIN.CPP
  include: C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\2019\PREVIEW\VC\TOOLS\MSVC\14.29.30031\INCLUDE
  include: C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\UM
  include: C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\UCRT
  include: C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\SHARED
  include: C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\WINRT
  include: C:\PROGRAM FILES (X86)\WINDOWS KITS\10\INCLUDE\10.0.19041.0\CPPWINRT
  define: _DEBUG
  define: UNICODE
  define: _UNICODE
  stdver: ms_c++latest
  intelliSenseMode: windows-msvc-x64
Queueing IntelliSense update for files in translation unit of: C:\USERS\SAM HUANG\PROJECTS\CPPTOOLS-REPRO-SANDBOX\MAIN.CPP
cpptools/finishUpdateSquiggles
Error squiggle count: 2
Update IntelliSense time (sec): 0.633
cpptools/getCodeActions: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 5)
cpptools/getFoldingRanges: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 6)
cpptools/abortRequest
cpptools/getFoldingRanges: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 7)
cpptools/getCodeActions: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 8)
cpptools/textEditorSelectionChange
cpptools/getCodeActions: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 9)
cpptools/activeDocumentChange: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp
cpptools/textEditorSelectionChange
idle loop: reparsing the active document
Checking for syntax errors: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp
Queueing IntelliSense update for files in translation unit of: C:\USERS\SAM HUANG\PROJECTS\CPPTOOLS-REPRO-SANDBOX\MAIN.CPP
cpptools/finishUpdateSquiggles
Error squiggle count: 1
Update IntelliSense time (sec): 0.267
cpptools/getSemanticTokens: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 10)
Database safe to open
cpptools/getFoldingRanges: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 11)
cpptools/getCodeActions: file:///c%3A/Users/Sam%20Huang/Projects/cpptools-repro-sandbox/main.cpp (id: 12)

Screenshots

Additional context

The text was updated successfully, but these errors were encountered:

sean-mcmanus · 2021-05-01T00:06:18Z

Thanks for reporting this. I've filed a bug on our shared VS parser. I'll add the URL once the bug becomes public.

sean-mcmanus · 2021-05-01T00:41:31Z

Filed at https://developercommunity.visualstudio.com/t/C20-IntelliSense-error-function-canno/1411924

sean-mcmanus · 2022-08-16T23:48:31Z

Fixed with https://github.com/microsoft/vscode-cpptools/releases/tag/v1.12.1

sean-mcmanus self-assigned this Apr 30, 2021

sean-mcmanus added bug Language Service Visual Studio Inherited from Visual Studio labels May 1, 2021

sean-mcmanus added this to the Tracking milestone May 1, 2021

sean-mcmanus removed their assignment May 1, 2021

sean-mcmanus modified the milestones: Tracking, 1.12.1 Aug 2, 2022

sean-mcmanus added the fixed Check the Milestone for the release in which the fix is or will be available. label Aug 2, 2022

sean-mcmanus closed this as completed Aug 31, 2022

github-actions bot locked and limited conversation to collaborators Oct 15, 2022

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Weird interaction with C++20's abbreviated function template #7446

Weird interaction with C++20's abbreviated function template #7446

sam20908 commented Apr 30, 2021 •

edited

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sean-mcmanus commented May 1, 2021

sean-mcmanus commented May 1, 2021

sean-mcmanus commented Aug 16, 2022

Weird interaction with C++20's abbreviated function template #7446

Weird interaction with C++20's abbreviated function template #7446

Comments

sam20908 commented Apr 30, 2021 • edited Loading

sean-mcmanus commented May 1, 2021

sean-mcmanus commented May 1, 2021

sean-mcmanus commented Aug 16, 2022

sam20908 commented Apr 30, 2021 •

edited

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