Coroutines: error when non-copyable/non-movable returned from `await_resume`

Comienza reproduciendo el informe en main.cpp con C++20 y la configuración de Windows MSVC IntelliSense descrita. Rastrea el diagnóstico en la expresión co_await cuando await_resume devuelve el foo no copiable; se considera terminado cuando IntelliSense no muestra ningún subrayado ondulado de error mientras los compiladores indicados siguen aceptando el código.

Environment

• OS and Version: Windows 11 25H2
• VS Code Version: 1.110.0
• C/C++ Extension Version: 1.30.5
• If using SSH remote, specify OS of remote machine: None

When returning a non-copyable and non-movable value from await_resume of an awaiter, intellisense reports this error at the co_await point (using MSVC as compiler): function "foo::foo(foo &&)" cannot be referenced -- it is a deleted function.

Nevertheless, MSVC, GCC and Clang accept the code and the program behaves as expected.

Bug Summary and Steps to Reproduce

Bug Summary:

Steps to reproduce: Paste the following snippet:

#include <coroutine>
#include <exception>

struct fire_and_forget final
{
    struct promise_type;
};

struct fire_and_forget::promise_type final
{
    static constexpr fire_and_forget get_return_object() noexcept { return {}; }
    static constexpr std::suspend_never initial_suspend() noexcept { return {}; }
    static constexpr std::suspend_never final_suspend() noexcept { return {}; }

    static constexpr void return_void() noexcept {}
    inline static void unhandled_exception() noexcept { std::terminate(); }
};


struct foo final
{
    foo() = default;

    foo(foo const &) = delete;
    foo &operator=(foo const &) = delete;

    foo(foo &&) = delete;
    foo &operator=(foo &&) = delete;
};

struct my_awaiter final
{
    bool await_ready() { return false; }
    void await_suspend(auto) {}
    foo await_resume() { return foo{}; }
};

fire_and_forget test()
{
    auto x = co_await my_awaiter{}; // error here
}

Expected behavior: No error squiggles

Configuration and Logs

// c_cpp_properties.json

{
    "configurations": [
        {
            "name": "Win32",
            "includePath": [
                "${workspaceFolder}/**",
                "${workspaceFolder}/src"
            ],
            "defines": [
                "_DEBUG",
                "UNICODE",
                "_UNICODE"
            ],
            "windowsSdkVersion": "10.0.26100.0",
            "intelliSenseMode": "windows-msvc-x64"
        }
    ],
    "version": 4
}

C/C++: Log Diagnostics

-------- Diagnostics - 3/5/2026, 12:04:00 PM
Version: 1.30.5
Current Configuration:
{
    "name": "Win32",
    "includePath": [
        "<User>/thing/cpp/entt_scheduler_demo/**",
        "<User>/thing/cpp/entt_scheduler_demo/src"
    ],
    "defines": [
        "_DEBUG",
        "UNICODE",
        "_UNICODE"
    ],
    "windowsSdkVersion": "10.0.26100.0",
    "intelliSenseMode": "windows-msvc-x64",
    "compilerPathIsExplicit": true,
    "cStandardIsExplicit": true,
    "cppStandardIsExplicit": true,
    "intelliSenseModeIsExplicit": true,
    "recursiveIncludesReduceIsExplicit": false,
    "recursiveIncludesPriorityIsExplicit": false,
    "recursiveIncludesOrderIsExplicit": false,
    "cStandard": "c17",
    "cppStandard": "c++20",
    "mergeConfigurations": false,
    "recursiveIncludes": {},
    "compilerPath": "${env:CXX}",
    "browse": {
        "limitSymbolsToIncludedHeaders": true
    }
}
Modified Settings:
{
    "C_Cpp.inlayHints.autoDeclarationTypes.enabled": true,
    "C_Cpp.inlayHints.parameterNames.enabled": true,
    "C_Cpp.autocompleteAddParentheses": true,
    "C_Cpp.errorSquiggles": "enabled",
    "C_Cpp.default.compilerPath": "${env:CXX}",
    "C_Cpp.default.cStandard": "c17",
    "C_Cpp.default.cppStandard": "c++20",
    "C_Cpp.commentContinuationPatterns": [
        "/*"
    ],
    "C_Cpp.codeAnalysis.clangTidy.enabled": true,
    "C_Cpp.codeAnalysis.clangTidy.args": [
        "-isystem=CMakeLists.txt",
        "*"
    ],
    "C_Cpp.codeAnalysis.clangTidy.checks.disabled": [
        "cppcoreguidelines-avoid-magic-numbers",
        "cppcoreguidelines-avoid-c-arrays",
        "fuchsia-default-arguments-calls",
        "fuchsia-default-arguments-declarations",
        "fuchsia-overloaded-operator",
        "hicpp-avoid-c-arrays",
        "llvm-include-order",
        "llvm-header-guard",
        "llvmlibc-*",
        "modernize-avoid-c-arrays",
        "readability-magic-numbers"
    ],
    "C_Cpp.experimentalFeatures": "enabled"
}
Additional Tracked Settings:
{
    "editorTabSize": 4,
    "editorInsertSpaces": true,
    "editorAutoClosingBrackets": "languageDefined",
    "filesEncoding": "utf8",
    "filesAssociations": {},
    "filesExclude": {
        "**/.git": true,
        "**/.svn": true,
        "**/.hg": 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): 1.30.5.0
Current database path: <User>\APPDATA\LOCAL\MICROSOFT\VSCODE-CPPTOOLS\8867B49488CF20A004321616C2AF107D\.BROWSE.VC.DB
Translation Unit Mappings:
[ <User>\thing\cpp\entt_scheduler_demo\main.cpp - source TU]:
Translation Unit Configurations:
[ <User>\thing\cpp\entt_scheduler_demo\main.cpp ]
    Process ID: 25624
    Memory Usage: 85 MB
    Compiler Path: C:\Program Files\Microsoft Visual Studio\18\Community\VC\Tools\MSVC\14.50.35717\bin\Hostx64\x64\cl.exe
    Include paths:
        include: <User>\thing\cpp\entt_scheduler_demo\src
        system include: C:\Program Files\Microsoft Visual Studio\18\Community\VC\Tools\MSVC\14.50.35717\include
        system include: C:\Program Files\Microsoft Visual Studio\18\Community\VC\Tools\MSVC\14.50.35717\atlmfc\include
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\um
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\shared
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\winrt
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\cppwinrt
    Defines:
        _DEBUG
        UNICODE
        _UNICODE
    Standard Version: ms_c++20
    IntelliSense Mode: windows-msvc-x64
Total Memory Usage: 85 MB

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 5892

Other Extensions

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Additional context

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