&optionalpackage → t
use-package checks for name conflicts between the newly imported symbols and those already accessible in package.
A name conflict in use-package between two external symbols inherited by package from packages-to-use may be resolved in favor of either symbol by importing one of them into package and making it a shadowing symbol.
(use-package 'trash 'temp)
(#<PACKAGE "TEMP"> #<PACKAGE "TRASH">)
(find-symbol "LAND-FILL" 'temp)
The use list of package may be modified.