I'm no sure if "autohinting" is correct word but I can explain
for example when I write
std::
I want to see the list of available things there, and same for "." and "->" , I hope that is possible.
You can bind . and > with semantic-complete-self-insert command, that will try to show list of possible completions. Although I don't know, is it possible out of box to bind it to :: sequence (although, it should be possible with some amount of emacs lisp code)