I tried zsh -n to see how good a tool it might be for lint checking. Overall
it works very well.

However I ran into a problem when using a string associative array index.
Here's a sample run:

$ cat /tmp/zsh-bug.sh
> typeset -A hash
> hash['display']=5
> echo ${hash['display']}
> $ zsh /tmp/zsh-bug.sh
> 5
> $ zsh -n /tmp/zsh-bug.sh
> /tmp/zsh-bug.sh:2: bad math expression: operand expected at `'display''
> /tmp/zsh-bug.sh:3: bad math expression: operand expected at `'display''
> $ zsh --version
> zsh 4.3.10 (i686-pc-linux-gnu)
> $


By the way, I also tried ksh -n from version 93u- 2010-09-22. It also
catches basic syntax errors such as with
complex statements (if, while, case, for) but offers a number of lint- like
suggestions such as to improve speed and and allow for better
ksh conformance. Out of 57 or so files I tried in the zshdb
distribution, there were about 5 errors which I don't think anythingn could
be done about, i.e. legitimate differences between zsh and ksh. However
there were many  warnings for performance improvements, removing deprecated
constructs and better ksh conformance.