1. Enable the ClangCodeModel plugin and restart Creator.
2. In "Tools" -> "Options..." -> "C++" -> "Code Model", enable Clang for all file types.
3. Create a new Plain C++ Project.
4. After the first line in main.cpp, add a broken include.
   The first line, which is correct, will be underlined.
5. Hover the first line with the mouse.
   You'll see a tooltip: "'<filename>' file not found":
   
6. Close and reopen main.cpp.
   The underline of the first line and the tooltip are gone.

When there's an error in the code, only the wrong line should be underlined.

When using Creator's built-in code model, these error indicators will only be shown in the right location.