What is the use of zap trash in Homebrew formulae?

[ok-coder1]

Output of brew config

Not needed

Output of brew doctor

Not needed

Description of issue

I didn't understand the purpose of zap trash in formulae.

[p-linnane]

zap only works in casks, not formulae.

From the Cask Cookbook:

The zap stanza describes a more complete uninstallation of files associated with a cask.

zap stanzas may remove:
Preference files and caches stored within the user’s ~/Library directory.
Shared resources such as application updaters. Since shared resources may be removed, other applications may be affected by brew uninstall --zap. Understanding that is the responsibility of the end user.