F12::scaHELLOWORLD() ; no function defined with this name
In the thread forum user Helgef identified the problem as the line being interpreted as a remapping
scais the 9-key in the top row of the keyboard.
This is in contradiction to the documentation: https://autohotkey.com/docs/Hotkeys.htm#Intro
Hotkeys wrote:However, if a hotkey needs to execute only a single line, that line can be listed to the right of the double-colon.
After about two days no more responses were posted in the thread, so I think this might be an unknown bug.
I tested on Win10 64-bit with AHK v1.1.26.01 64-bit.