When you use the locate widget to search for symbol declarations or implementations, it should display the file name it's found the result in. At the very least, it should do that if more than one result is found.

Very often when searching for functions in QtCore, they may exist in multiple files (often _unix.cpp and _win.cpp), and it's somewhat random in which order they show up. I tried to check today if they appear sorted by filename alphabetical order, but the _win.cpp entry was the second (middle) one.

Side-suggestion: when searching for things in the current file (Ctrl+k .), it should display the line number.