When I have a Class name in red, I used to be able to mouse-over it (or something -- I never could figure out the logic definitively) and see a guess or several offered for adding an import to the right class automatically. ALT+enter (or CMD+enter... I have no idea) used to select this suggestion. Now, however, the same key stroke simply dismisses the suggestion and no import suggestions are ever offered again for the class.
What is/was this function I used to invoke by ALT+enter or CMD+enter, and how can I restore its working order?