Remove MacOS definition from generic OS

We don't want to define `MacOS` in the generic OS, so let's make sure we
refer to it as `OS::Mac` in the places we need it.

This reverts commit 575cb0263cb1428c63b9428bbd913ffde83bd317.

Library/Homebrew/dev-cmd/determine-test-runners.rb

@@ -46,7 +46,7 @@ class TestRunnerFormula
     formula.requirements.find { |r| r.is_a?(MacOSRequirement) && r.version_specified? }
   end
 
-  sig { params(macos_version: MacOS::Version).returns(T::Boolean) }
+  sig { params(macos_version: OS::Mac::Version).returns(T::Boolean) }
   def compatible_with?(macos_version)
     # Assign to a variable to assist type-checking.
     requirement = versioned_macos_requirement
@@ -93,7 +93,7 @@ module Homebrew
       testing_formulae:     T::Array[TestRunnerFormula],
       reject_platform:      T.nilable(Symbol),
       reject_arch:          T.nilable(Symbol),
-      select_macos_version: T.nilable(MacOS::Version),
+      select_macos_version: T.nilable(OS::Mac::Version),
     ).returns(T::Boolean)
   }
   def self.formulae_have_untested_dependents?(testing_formulae, reject_platform:, reject_arch:, select_macos_version:)
@@ -123,7 +123,7 @@ module Homebrew
       deleted_formulae:     T.nilable(T::Array[String]),
       reject_platform:      T.nilable(Symbol),
       reject_arch:          T.nilable(Symbol),
-      select_macos_version: T.nilable(MacOS::Version),
+      select_macos_version: T.nilable(OS::Mac::Version),
     ).returns(T::Boolean)
   }
   def self.add_runner?(formulae,
@@ -200,7 +200,7 @@ module Homebrew
     ephemeral_suffix = "-#{github_run_id}-#{github_run_attempt}"
 
     MacOSVersions::SYMBOLS.each do |symbol, version|
-      macos_version = MacOS::Version.new(version)
+      macos_version = OS::Mac::Version.new(version)
       next if macos_version.outdated_release? || macos_version.prerelease?
 
       if args.dependents?

Library/Homebrew/extend/on_system.rb

@@ -28,13 +28,13 @@ module OnSystem
 
     return false if Homebrew::SimulateSystem.simulating_or_running_on_linux?
 
-    base_os = MacOS::Version.from_symbol(os_name)
+    base_os = OS::Mac::Version.from_symbol(os_name)
     current_os = if Homebrew::SimulateSystem.current_os == :macos
       # Assume the oldest macOS version when simulating a generic macOS version
       # Version::NULL is always treated as less than any other version.
       Version::NULL
     else
-      MacOS::Version.from_symbol(Homebrew::SimulateSystem.current_os)
+      OS::Mac::Version.from_symbol(Homebrew::SimulateSystem.current_os)
     end
 
     return current_os >= base_os if or_condition == :or_newer

Library/Homebrew/os.rb

@@ -55,7 +55,6 @@ module OS
   LINUX_PREFERRED_GCC_COMPILER_FORMULA = "gcc@11" # https://packages.ubuntu.com/jammy/gcc
   LINUX_PREFERRED_GCC_RUNTIME_FORMULA = "gcc"
 
-  require "os/generic"
   if OS.mac?
     require "os/mac"
     # Don't tell people to report issues on unsupported configurations.

Library/Homebrew/os/generic.rb

@@ -1,8 +0,0 @@
-# typed: strict
-# frozen_string_literal: true
-
-module OS
-  module Mac
-    ::MacOS = OS::Mac
-  end
-end

Library/Homebrew/os/linux.rb

@@ -54,6 +54,8 @@ module OS
   module Mac
     module_function
 
+    ::MacOS = OS::Mac
+
     raise "Loaded OS::Linux on generic OS!" if ENV["HOMEBREW_TEST_GENERIC_OS"]
 
     def version

Library/Homebrew/os/mac.rb

@@ -13,6 +13,8 @@ module OS
 
     module_function
 
+    ::MacOS = OS::Mac
+
     raise "Loaded OS::Mac on generic OS!" if ENV["HOMEBREW_TEST_GENERIC_OS"]
 
     VERSION = ENV.fetch("HOMEBREW_MACOS_VERSION").chomp.freeze

Library/Homebrew/requirements/macos_requirement.rb

@@ -23,9 +23,9 @@ class MacOSRequirement < Requirement
   def initialize(tags = [], comparator: ">=")
     @version = begin
       if comparator == "==" && tags.first.respond_to?(:map)
-        tags.first.map { |s| MacOS::Version.from_symbol(s) }
+        tags.first.map { |s| OS::Mac::Version.from_symbol(s) }
       else
-        MacOS::Version.from_symbol(tags.first) unless tags.empty?
+        OS::Mac::Version.from_symbol(tags.first) unless tags.empty?
       end
     rescue MacOSVersionError => e
       if DISABLED_MACOS_VERSIONS.include?(e.version)
@@ -43,7 +43,7 @@ class MacOSRequirement < Requirement
       end
 
       # Otherwise fallback to the oldest allowed if comparator is >=.
-      MacOS::Version.new(HOMEBREW_MACOS_OLDEST_ALLOWED) if comparator == ">="
+      OS::Mac::Version.new(HOMEBREW_MACOS_OLDEST_ALLOWED) if comparator == ">="
     end
 
     @comparator = comparator
@@ -56,7 +56,7 @@ class MacOSRequirement < Requirement
 
   satisfy(build_env: false) do
     T.bind(self, MacOSRequirement)
-    next Array(@version).any? { |v| MacOS.version.public_send(@comparator, v) } if OS.mac? && version_specified?
+    next Array(@version).any? { |v| OS::Mac.version.public_send(@comparator, v) } if OS.mac? && version_specified?
     next true if OS.mac?
     next true if @version