Template Variable Specialization Error: "variable xx has already been initialized"

[Zehua-Chen]

Type: LanguageService

Describe the bug

• OS and Version: macOS 10.14.12
• VS Code Version: 1.30.2
• C/C++ Extension Version: 0.21.0
• Other extensions you installed (and if the issue persists after disabling them):
  • C#
  • C# XML Documentation
  • CMake
  • Debugger for Unity
  • LaTeX Workshop
  • One Dark Pro
  • Pola Code
  • Verilog HDL/SystemVerilog
  • vscode-icons
  • x86 and x86_64 Assembly
• A clear and concise description of what the bug is.

In the json parser that I am working on, I am using template variables as a part of my parser so that my parser would work with all types of chars in C++. The file that's causing the problem looks like the following snippet, but with a lot more template variables.

template<typename CharT>
inline constexpr CharT beginObject{};

template<>
inline constexpr char beginObject<char>{ '{' };

The clang++ compiler that I have on my mac (Apple LLVM version 10.0.0 (clang-1000.11.45.5)) compiles the code just fine, but vs code produces the following error:

variable "beginObject [with CharT=char]" has already been initialized

To Reproduce

0. Set settings.json as follows

{
    "C_Cpp.default.cppStandard": "c++17"
}

1. Create a main.cpp file;
2. Copy and paste the following into the main file

// #include "gtest/gtest.h"
#include <iostream>

template<typename CharT>
CharT letter{};

template<>
char letter<char>{ 'a' };

int main(int argc, char **argv)
{
    std::cout << letter<char> << std::endl;
    // testing::InitGoogleTest(&argc, argv);
    // return RUN_ALL_TESTS();
    return 0;
}

3. After the red flame goes off, the error should occur;
4. To compile, use the following compiler flags (clang)

-std=c++17

(The actual project file that's causing the error looks very similar to this, but with a lot more template variables used in the json parser and does not have the main function. I am happy to provide the source code if needed.)

Expected behavior

There should be no errors from the plugin, as the compiler compiles the code just fine.

Screenshots

Additional context

[YassinMahmoudEl-Zouhery]

is there any issue

[Zehua-Chen]

Yes, the plugin is throwing a syntax error when the compiler does not.

[bobbrow]

@sean-mcmanus this looks like a bug we had in the past. Did we get a fix for it yet?

[sean-mcmanus]

It got resolved as Won't Fix by the VS team -- we'll try to get it re-opened.

https://developercommunity.visualstudio.com/content/problem/281377/intellisense-problem-1.html
https://developercommunity.visualstudio.com/content/problem/368977/intellisence-error-when-using-variable-template-sp.html
https://developercommunity.visualstudio.com/content/problem/398349/intellisense-error-when-using-variable-template-sp.html

[sean-mcmanus]

They re-opened https://developercommunity.visualstudio.com/content/problem/281377/intellisense-problem-1.html so you can upvote that.

[sean-mcmanus]

The fix for this incorrect IntelliSense error is in the latest Insiders version of the extension: https://github.com/Microsoft/vscode-cpptools/releases/tag/0.22.2-insiders

[Zehua-Chen]

Thanks!