1. Make a kit using Qt 5.9 your default kit.
2. Create a new Qt Widgets Application project.
3. Close the project.
4. Remove the .pro.user file from the project's source directory.
5. Open the project again but do not configure it.
6. Open Projects view.
   The project did not finish parsing. Only the .pro file is visible.
7. Open the General Messages view.
   You'll see a message like:

   D:/dev/src/qt-5.9.0-beta3/qtbase/mkspecs/features/toolchain.prf(129): Variable QMAKE_CXX.COMPILER_MACROS is not defined.
   Project ERROR: msvc-version.conf loaded but QMAKE_MSC_VER isn't set
   Error while parsing file D:\Testprojekte\untitled876\untitled876.pro. Giving up.
   

Creator should be able to parse the project before configuring it. When a kit using Qt 5.8 is the default kit, this works fine.