When you reference a symbol that has not yet been imported, CLion helps you to locate the file (header, as a rule) which contains declaration (definition) of that symbol and adds it to the list of includes.
The import statement is added to the imports section, but the cursor does not move from the current position, and your current editing session does not suspend. This feature is known as the Import Assistant.
The same possibility applies to the XML files. When you type a tag with an unbound namespace, the import assistant suggests to create a namespace and offers a list of appropriate choices.
Importing missing header files
If you know that a class or function exists in your project or in a standard C/C++ library, use it in your code.
To import a header file, follow these steps:
Type a reference to a non-imported class or function.
Press Alt+Enter. If there are multiple choices, select the desired import from the list.