Things that would be useful to see in a language.
A common idiom is looping "forever" (well, practically you need to exit that loop at some time).
forever { ... }
instead of
while (true) { ... }
The idea is that the keyword forever stands out more obviously to the reader, making it clearer what's going on. In a language like C, you could define a macro forever to be replaced by while (1). Either way, the compiler should be on the lookout for perpetual loops, and check that there is a path out of it (some sort of accessible break; somewhere). Not finding a way out should be a warning, not an error, as there is GUI code which loops forever (?).