IntelliSense false error: compound requirement in hidden friend of a class template

[Li-Xiang-Ideal]

Environment

• OS and Version: Windows 10 Pro 22H2, x64
• VS Code Version: 1.134.0
• C/C++ Extension Version: 1.33.8 (cpptools native version 1.33.7.0)
• Compiler: MSYS2 MinGW-w64 GCC 16.1.0

Bug Summary and Steps to Reproduce

Bug Summary:

IntelliSense incorrectly rejects a constrained hidden-friend function template declared inside a class template.

Sample code:

#include <concepts>

template <typename>
struct Box {
    template <typename T>
    requires requires(T value) {
        { value } -> std::same_as<T&>;
    }
    friend Box operator+(const T&, Box box) {
        return box;
    }
};

Box<int> box;
auto result = 0 + box;

IntelliSense reports:

no operator "+" matches these operands C/C++(349)
minimal_repro.cpp(15, 17): operand types are: int + Box<int>
minimal_repro.cpp(15, 17): substituting "<int>" for function template "operator+" failed constraints
minimal_repro.cpp(15, 17): atomic constraint evaluates to false
minimal_repro.cpp(15, 17): built-in operator+(<promoted arithmetic>, <promoted arithmetic>) does not match because argument #2 does not match parameter
minimal_repro.cpp(15, 17): built-in operator+(<pointer to object>, <ptrdiff_t>) does not match because argument #1 does not match parameter
minimal_repro.cpp(15, 17): built-in operator+(<ptrdiff_t>, <pointer to object>) does not match because argument #2 does not match parameter

Expected behavior:

There should be no error. value is an lvalue expression, so decltype((value)) is T& and the compound requirement is satisfied.

GCC 16.1 accepts the file with no output:

g++ -std=c++23 -fsyntax-only -Wall -Wextra -Wpedantic minimal_repro.cpp

It also accepts the file with -std=c++20.

Configuration and Logs

No c_cpp_properties.json is used; the configuration comes from C_Cpp.default.* settings.
Workspace-specific paths have been replaced with _, and unrelated entries have been omitted.

-------- Diagnostics
Version: 1.33.8
Current Configuration:
{
    "name": "Win32",
    "includePath": [
        "D:/_/**",
        "C:/msys64/mingw64/include"
    ],
    "windowsSdkVersion": "10.0.22621.0",
    "defines": [
        "_DEBUG",
        "UNICODE",
        "_UNICODE"
    ],
    "cStandard": "c23",
    "cppStandard": "c++23",
    "intelliSenseMode": "windows-gcc-x64",
    "intelliSenseModeIsExplicit": true,
    "cStandardIsExplicit": true,
    "cppStandardIsExplicit": true,
    "mergeConfigurations": false,
    "compilerPath": "C:/msys64/mingw64/bin/g++.exe",
    "compilerPathIsExplicit": true,
    "browse": {
        "limitSymbolsToIncludedHeaders": true
    }
}
cpptools version (native): 1.33.7.0
Translation Unit Mappings:
[ D:\_\minimal_repro.cpp - source TU]:
Translation Unit Configurations:
[ D:\_\minimal_repro.cpp ]
    Compiler Path: C:\msys64\mingw64\bin\g++.exe
    Language: C++
    Include Paths:
        system include: C:\msys64\mingw64\include\c++\16.1.0
        system include: C:\msys64\mingw64\include\c++\16.1.0\x86_64-w64-mingw32
        system include: C:\msys64\mingw64\include\c++\16.1.0\backward
        system include: C:\msys64\mingw64\lib\gcc\x86_64-w64-mingw32\16.1.0\include
        system include: C:\msys64\mingw64\include
        system include: C:\msys64\mingw64\lib\gcc\x86_64-w64-mingw32\16.1.0\include-fixed
        include (recursive): D:\_
    Defines:
        _DEBUG
        UNICODE
        _UNICODE
    Standard Version: c++23
    IntelliSense Mode: windows-gcc-x64
    Other Flags:
        --g++
        --gnu_version=160100

Other Extensions

No response

Additional context

• Changing template <typename> struct Box to struct Box removes the IntelliSense error.

• Replacing { value } -> std::same_as<T&>; with the simple requirement value; removes the IntelliSense error.

• The following self-type variant is still incorrectly evaluated as false:

  { value } -> std::same_as<decltype((value))>;

This may be related to the general class of GCC 16 IntelliSense errors tracked in #14464, but it is different from the cases listed there. That issue was assigned to the 1.33.5 milestone, while this reproduction still occurs with C/C++ extension 1.33.8.