When typing a function, code completion doesn't seem to switch contexts like it has in the past. Steps to replicate:
1. Create a new Qt Widgets application
2. In the constructor for MainWindow.cpp, start typing the following line of code:
connect(this,&MainWindow::destroyed, this,&MainWindow::deleteLater);
3. Upon typing the first '&' the tooltip is still showing the function prototype for the connect() function (see autocomplete1.png). With previous versions of Qt Creator, autocomplete would popup suggestion you want to type "MainWindow" (see old_autocomplete.png).

Qt versions I've tested:
3.2.2 doesn't work
3.4.1 works correctly
3.4.2 works correctly
3.6.1 works correctly
4.0.0 doesn't work
4.0.1 (18-May-2016 snapshot) doesn't work