Pass around only pathname objects

Library/Homebrew/extend/pathname.rb

@@ -37,9 +37,8 @@ class Pathname
   def install_p(src, new_basename)
     raise Errno::ENOENT, src.to_s unless File.symlink?(src) || File.exist?(src)
 
-    src = src.to_s
-    dst = join(new_basename).to_s
-
+    src = Pathname(src)
+    dst = join(new_basename)
     dst = yield(src, dst) if block_given?
 
     mkpath
@@ -48,7 +47,7 @@ class Pathname
     # is a symlink, and its target is moved first, FileUtils.mv will fail:
     #   https://bugs.ruby-lang.org/issues/7707
     # In that case, use the system "mv" command.
-    if File.symlink? src
+    if src.symlink?
       raise unless Kernel.system 'mv', src, dst
     else
       FileUtils.mv src, dst

Library/Homebrew/install_renamed.rb

@@ -1,7 +1,7 @@
 module InstallRenamed
   def install_p(_, new_basename)
     super do |src, dst|
-      if File.directory?(src)
+      if src.directory?
         dst
       else
         append_default_if_different(src, dst)
@@ -25,10 +25,11 @@ module InstallRenamed
 
   private
 
-  def append_default_if_different src, dst
-    if File.file? dst and !FileUtils.identical?(src, dst)
-      dst += ".default"
+  def append_default_if_different(src, dst)
+    if dst.file? && !FileUtils.identical?(src, dst)
+      Pathname.new("#{dst}.default")
+    else
+      dst
     end
-    dst
   end
 end