Qt creator, CMake and c++17 code model.

  • Hi, everybody. I write code in qt-creator 4.8.0 + cmake (on linux). When using the std::get and std::variant functions, if std::visit is called in the same translation unit, the IDE generates many errors.

    class Foo {
        int a{1};
        int b{2};
        void set_a(const int new_a) { a = new_a; }
    class Bat {
        int Arr[200]{};
    int main() {
        int a;
        cin >> a;
        std::variant<Foo, Bat> var_1;
        if (a == 0)
            var_1 = Foo();
            var_1 = Bat();
        std::variant<Foo, Bat> var_2;
            [](auto& arg) {
        std::get<Foo>(var_1).a = 444;
        std::get<Foo>(var_1).set_a(124);        // IDE throws an error (this argument to member function 'set_a' fas type 'const Foo', but function is not marked const)
        cout << std::get<Foo>(var_1).a << endl;
        return 0;

    CMake script:

        cmake_minimum_required(VERSION 3.10)
        set(CMAKE_CXX_STANDARD 17)
        add_executable(${PROJECT_NAME} "main.cpp")

    Despite this, the code is compiled (GCC 7.3). I have a section of code where std::get is actively used, and after adding a call to std::visit, qt-creator has colored the 2к code lines in red. How can I fix this?

  • Lifetime Qt Champion

    Hi and welcome to devnet,

    You may have unearthed a shortcoming from Qt Creator's current code model. You should check the bug report system to see if it's something known.

  • @SGaist I didn't find my issue there. Should I write a bug report?

  • Lifetime Qt Champion

    One thing you can do is test the Qt Creator 4.9 Beta. If you still have the issue with it, then yes, please open a report.

  • Qt Champions 2018

    That's QTCREATORBUG-21873 now.

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