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  1. Qt
  2. QTBUG-104899

QML(_NAMED)_ELEMENT should generate a clear error if the type in not default constructible

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    • 6bdeafcad (dev), 83697e49e (6.5)

    Description

      If a type is marked with QML_ELEMENT, but does not have a default ctor, it becomes uncreatable. Unless the type has been explicitly marked as such, that should create an actionable warning message, or even a compile time error.

       

      We might be able to get a compilation error by having the macro expand to 

      consteval void check() {
    using Self = std::remove_cvref_t<decltype(*this);
    static_assert(!std::is_default_constructible<Self>> || is_uncreatable<Self>);
}

      However, we would need to evaluate the compile time overhead of such a solution, and potentially deal with shadowing warning.

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          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-106093 No specific warning when trying to expose a C++ type to QML which has no default constructor

          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-87834 Provide a more detailed error message when a C++ type that's exposed to QML cannot be created

          • P3: Somewhat important - Should be fixed, but doesn't affect the release in any way.
          • Closed
          For Gerrit Dashboard: QTBUG-104899
          # Subject Branch Project Status CR V
          454308,6 QML: Output a warning for creatable object types without default ctor dev qt/qtdeclarative Status: MERGED +2 0
          455827,2 QML: Output a warning for creatable object types without default ctor 6.5 qt/qtdeclarative Status: MERGED +2 0

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              ulherman Ulf Hermann
              fabiankosmale Fabian Kosmale
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              Dates

                Created:
                Updated:
                Resolved:

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