X11Dependency: use Version objects

Library/Homebrew/requirements/x11_dependency.rb

@@ -11,12 +11,16 @@ class X11Dependency < Requirement
 
   def initialize(name="x11", tags=[])
     @name = name
-    @min_version = tags.shift if /(\d\.)+\d/ === tags.first
+    if /(\d\.)+\d/ === tags.first
+      @min_version = Version.new(tags.shift)
+    else
+      @min_version = Version.new("0.0.0")
+    end
     super(tags)
   end
 
   satisfy :build_env => false do
-    MacOS::XQuartz.installed? && (@min_version.nil? || @min_version <= MacOS::XQuartz.version)
+    MacOS::XQuartz.installed? && min_version <= Version.new(MacOS::Quartz.version)
   end
 
   def message; <<-EOS.undent
@@ -27,16 +31,7 @@ class X11Dependency < Requirement
   end
 
   def <=> other
-    return nil unless X11Dependency === other
+    return unless X11Dependency === other
-
+    min_version <=> other.min_version
-    if min_version.nil? && other.min_version.nil?
-      0
-    elsif other.min_version.nil?
-      1
-    elsif min_version.nil?
-      -1
-    else
-      min_version <=> other.min_version
-    end
   end
 end

Library/Homebrew/test/test_dependency_collector.rb

@@ -69,7 +69,7 @@ class DependencyCollectorTests < Homebrew::TestCase
 
   def test_x11_min_version
     @d.add :x11 => '2.5.1'
-    assert_equal "2.5.1", find_requirement(X11Dependency).min_version
+    assert_equal "2.5.1", find_requirement(X11Dependency).min_version.to_s
   end
 
   def test_x11_tag
@@ -80,7 +80,7 @@ class DependencyCollectorTests < Homebrew::TestCase
   def test_x11_min_version_and_tag
     @d.add :x11 => ['2.5.1', :optional]
     dep = find_requirement(X11Dependency)
-    assert_equal '2.5.1', dep.min_version
+    assert_equal '2.5.1', dep.min_version.to_s
     assert_predicate dep, :optional?
   end