There was a recent thread about how someone executed

$ git add foo().bar

and was surprised to end up with three functions named "git", "add", and
"foo". So I decided to add

unsetopt multifuncdef

to my ~/.zshrc as one person who replied suggested to avoid that surprising
behavior. Imagine my surprise when a few days later I rebooted my computer
and found that any attempt to perform tab-completion resulted in this error:

_main_complete:143: parse error near `()'

I'm sorry but that's the final straw to break this camel's back. I've
either personally experienced, or read about others experiencing,  too many
problems of that nature. I'm going to switch to a shell whose behavior is
not impossible to understand or predict.

http://www.skepticism.us/2015/10/its-time-to-replace-zsh-with-a-saner-shell-because-unsetopt-multifuncdef-breaks-tab-completion/

P.S., Yes, I understand I could simply file a bug report to make the
standard completion code robust in the face of a user unsetting that
option. The point is that this is not an isolated incident. It reflects a
fundamental problem with zsh trying to be all things to all people.

-- 
Kurtis Rader
Caretaker of the exceptional canines Junior and Hank