follow the pattern more closely

Library/Homebrew/extend/os/dependency_collector.rb

+require "dependency_collector"
+
 if OS.mac?
   require "extend/os/mac/dependency_collector"
 elsif OS.linux?

Library/Homebrew/extend/os/linux/dependency_collector.rb

-def ant_dep(spec, tags)
-  Dependency.new(spec.to_s, tags)
+class DependencyCollector
+  def ant_dep(spec, tags)
+    Dependency.new(spec.to_s, tags)
+  end
 end

Library/Homebrew/extend/os/mac/dependency_collector.rb

-def ant_dep(spec, tags)
-  if MacOS.version >= :mavericks
-    Dependency.new(spec.to_s, tags)
+class DependencyCollector
+  def ant_dep(spec, tags)
+    if MacOS.version >= :mavericks
+      Dependency.new(spec.to_s, tags)
+    end
   end
 end