I found issue about not colorizing class name placed in global function. The example you can find in KDevelop project (master and 5.0 branches) in file: "kdevelopsessions.cpp". Properly code is placed on the top of this file and looks like below:
bool kdevelopsessions_runner_compare_sessions(const Session &s1, const Session &s2) {
  QCollator c;
  return c.compare(s1.name, s2.name) < 0;
}
Having bright (white) background in editor one can easily notice then QCollator name is not colorized. To be sure one can move mouse cursor over this class name expecting tool tip helper, whilst nothing will happen. I mean nothing is shown, and should.
When I put there, for example, following declaration: "QWidget w;" then it is properly colorized and helper tool tip is showing after mouse cursor will be over "QWidget".

Reproducible: Always

Steps to Reproduce:
1. Run KDevelop
2. Open KDevelop project (branch master or 5.0)
3. Open kdevelopsessions.cpp file
4. Go on the top to get see function: "kdevelopsessions_runner_compare_sessions"
5. Move mouse cursor over QCollator name

Actual Results:  
Helper tool tip is not shown. Additionally QCollator is not colorized.

Expected Results:  
Should be shown Helper tool tip and name QCollator colorized.

KDevelop and KDevplatform cloned at 28.10.2015