qmake is not run automatically after adding class to project

Building/linking with MSVC2017 x64 fails on Windows 10 x64
Steps:
New File or Project > Non---Qt Project -> Plain C++ Application -> ... -> Build system: qmake -> Kits for project: Desktop Qt 5.9.1 MSVC2017 64bit > add a class to the project, include it in the main.cpp, printout a variable from the class -> building error(image)