Avoid warning under setopt warn_nested_var

[rwe]

Previously in a shell running with setopt warn_nested_var, the
following warning would be produced:

_zsh_highlight_main__precmd_hook:1: array parameter _zsh_highlight_main__command_type_cache set in enclosing scope in function _zsh_highlight_main__precmd_hook

The documentation for WARN_NESTED_VAR is:

Print a warning message when an existing parameter from an enclosing function scope, or global, is set in a function by an assignment or in math context. […] Where possible, use of typeset -g to set the parameter suppresses the error, but note that this needs to be used every time the parameter is set.

[rwe]

The CI failure appears unrelated to this PR's changes:

/work/highlighters/main/main-highlighter.zsh:1680: parse error near `}'

[danielshahaf]

No, it's a genuine failure. (Note it's on the correct line number and didn't happen on master.) Older zsh's don't support the reserved word version of typeset, only the builtin version, so they take the empty parentheses as an empty set of glob qualifiers. Does it work as two lines? — typeset -gA _zsh_highlight_main__command_type_cache; _zsh_highlight_main__command_type_cache=()

Once redrawhook is merged we should also merge #688 to put an end to this class of problem.

[rwe]

Blast, you're right! Unfortunately it does not suppress the warning if done as two lines. I figured this was a quick fix but it looks like this would be a problem for zsh < 5.1. There are probably workarounds but I am not very familiar with the older versions. Should I close this PR and just leave an issue about the warning?

[danielshahaf]

Unfortunately it does not suppress the warning if done as two lines.

Ah, my bad. I missed that the documentation actually warns about this.

There are probably workarounds but I am not very familiar with the older versions.

The main thing is that you can't use foo=(…) in the same line as typeset (or one of its aliases, e.g., local). We also avoid relying on special parameters provided by the zsh/parameter module: for example, we do use ${options}, but we have a fallback codepath for when zsh/parameter isn't available.

Anyway, I just pushed a different fix. Thanks for the report.