#compdef which whence where type

local expl

_description expl 'external command'
compadd "$expl[@]" "$@" - "${(k@)commands}" && ret=0
_description expl 'builtin command'
compadd "$expl[@]" "$@" - "${(k@)builtins}" && ret=0
_description expl 'shell function'
compadd "$expl[@]" "$@" - "${(k@)functions}" && ret=0
_description expl 'alias'
compadd "$expl[@]" "$@" - "${(k@)raliases}" && ret=0
_description expl 'reserved word'
compadd "$expl[@]" "$@" - "${(k@)reswords}" && ret=0