Only use MachOShim/ELFShim when required

Not including this globally in `Pathname` speeds up the creation of
other `Pathname` objects by ~200x making all of Homebrew faster.

Author: MikeMcQuaid

Library/Homebrew/build.rb

@@ -198,7 +198,7 @@ def install
             (formula.logs/"00.options.out").write \
               "#{formula.full_name} #{formula.build.used_options.sort.join(" ")}".strip
 
-            Pathname.prepend WriteMkpathExtension
+            Pathname.activate_extensions!
             formula.install
 
             stdlibs = detect_stdlibs

Library/Homebrew/cask/artifact/abstract_uninstall.rb

@@ -541,7 +541,10 @@ def uninstall_rmdir(*directories, **kwargs)
         end
       end
 
-      def undeletable?(target); end
+      sig { params(target: Pathname).returns(T::Boolean) }
+      def undeletable?(target)
+        !target.parent.writable?
+      end
     end
   end
 end

Library/Homebrew/cask/artifact/moved.rb

@@ -197,7 +197,10 @@ def delete(target, force: false, successor: nil, command: nil, **_)
         end
       end
 
-      def undeletable?(target); end
+      sig { params(target: Pathname).returns(T::Boolean) }
+      def undeletable?(target)
+        !target.parent.writable?
+      end
     end
   end
 end

Library/Homebrew/cask/artifact/symlinked.rb

@@ -82,7 +82,12 @@ def unlink(command: nil, **)
       end
 
       sig { params(command: T.class_of(SystemCommand)).void }
-      def create_filesystem_link(command); end
+      def create_filesystem_link(command)
+        Utils.gain_permissions_mkpath(target.dirname, command:)
+
+        command.run! "/bin/ln", args: ["--no-dereference", "--force", "--symbolic", source, target],
+                                sudo: !target.dirname.writable?
+      end
 
       # Check if the target file is a symlink that originates from a formula
       # with the same name as this cask, indicating a potential conflict

Library/Homebrew/cask/macos.rb

@@ -232,8 +232,8 @@ module Mac
       "/var/spool/mail",
       "/var/tmp",
     ]
-                  .to_set { |path| Pathname(path) }
-                  .freeze, T::Set[Pathname])
+                  .to_set { |path| ::Pathname.new(path) }
+                  .freeze, T::Set[::Pathname])
     private_constant :SYSTEM_DIRS
 
     # TODO: There should be a way to specify a containing
@@ -373,19 +373,19 @@ module Mac
       "~/Library/Widgets",
       "~/Library/Workflows",
     ]
-                        .to_set { |path| Pathname(path.sub(%r{^~(?=(/|$))}, Dir.home)).expand_path }
+                        .to_set { |path| ::Pathname.new(path.sub(%r{^~(?=(/|$))}, Dir.home)).expand_path }
                         .union(SYSTEM_DIRS)
-                        .freeze, T::Set[Pathname])
+                        .freeze, T::Set[::Pathname])
     private_constant :UNDELETABLE_PATHS
 
-    sig { params(dir: T.any(Pathname, String)).returns(T::Boolean) }
+    sig { params(dir: T.any(::Pathname, String)).returns(T::Boolean) }
     def self.system_dir?(dir)
-      SYSTEM_DIRS.include?(Pathname.new(dir).expand_path)
+      SYSTEM_DIRS.include?(::Pathname.new(dir).expand_path)
     end
 
-    sig { params(path: T.any(Pathname, String)).returns(T::Boolean) }
+    sig { params(path: T.any(::Pathname, String)).returns(T::Boolean) }
     def self.undeletable?(path)
-      UNDELETABLE_PATHS.include?(Pathname.new(path).expand_path)
+      UNDELETABLE_PATHS.include?(::Pathname.new(path).expand_path)
     end
   end
 end

Library/Homebrew/extend/module.rb

@@ -3,4 +3,9 @@
 
 class Module
   include T::Sig
+
+  # The inverse of <tt>Module#include?</tt>. Returns true if the module
+  # does not include the other module.
+  sig { params(mod: T::Module[T.anything]).returns(T::Boolean) }
+  def exclude?(mod) = !include?(mod)
 end

Library/Homebrew/extend/os/cask/artifact/abstract_uninstall.rb

@@ -2,4 +2,3 @@
 # frozen_string_literal: true
 
 require "extend/os/mac/cask/artifact/abstract_uninstall" if OS.mac?
-require "extend/os/linux/cask/artifact/abstract_uninstall" if OS.linux?

Library/Homebrew/extend/os/cask/artifact/moved.rb

@@ -2,4 +2,3 @@
 # frozen_string_literal: true
 
 require "extend/os/mac/cask/artifact/moved" if OS.mac?
-require "extend/os/linux/cask/artifact/moved" if OS.linux?

Library/Homebrew/extend/os/cask/artifact/symlinked.rb

@@ -2,4 +2,3 @@
 # frozen_string_literal: true
 
 require "extend/os/mac/cask/artifact/symlinked" if OS.mac?
-require "extend/os/linux/cask/artifact/symlinked" if OS.linux?