You can read the julia-dev
thread here. Basically, it's simply changing to respect the rule described in the arrays documentation:
The last function, fill!, is different in that it modifies an existing array instead of constructing a new one. As a convention, functions with this property have names ending with an exclamation point. These functions are sometimes called "mutating" functions, or "in-place" functions.
FWIW I think this is a good idea, at least for Base
.