feat: add os_version for casks

Library/Homebrew/cask/dsl.rb

@@ -452,6 +452,7 @@ module Cask
       @artifacts ||= ArtifactSet.new
     end
 
+    sig { returns(Pathname) }
     def caskroom_path
       cask.caskroom_path
     end
@@ -459,6 +460,7 @@ module Cask
     # The staged location for this cask, including version number.
     #
     # @api public
+    sig { returns(Pathname) }
     def staged_path
       return @staged_path if @staged_path
 
@@ -590,9 +592,15 @@ module Cask
       true
     end
 
+    sig { returns(T.nilable(MacOSVersion)) }
+    def os_version
+      nil
+    end
+
     # The directory `app`s are installed into.
     #
     # @api public
+    sig { returns(T.any(Pathname, String)) }
     def appdir
       return HOMEBREW_CASK_APPDIR_PLACEHOLDER if Cask.generating_hash?
 

Library/Homebrew/extend/os/cask/dsl.rb

@@ -0,0 +1,4 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "extend/os/mac/cask/dsl" if OS.mac?

Library/Homebrew/extend/os/mac/cask/dsl.rb

@@ -0,0 +1,23 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "cask/macos"
+
+module OS
+  module Mac
+    module Cask
+      module DSL
+        extend T::Helpers
+
+        requires_ancestor { ::Cask::DSL }
+
+        sig { returns(T.nilable(MacOSVersion)) }
+        def os_version
+          MacOS.full_version
+        end
+      end
+    end
+  end
+end
+
+Cask::DSL.prepend(OS::Mac::Cask::DSL)