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diff --git a/trunk/lib/rubygems/dependency.rb b/trunk/lib/rubygems/dependency.rb
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+++ b/trunk/lib/rubygems/dependency.rb
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+#--
+# Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
+# All rights reserved.
+# See LICENSE.txt for permissions.
+#++
+
+require 'rubygems'
+
+##
+# The Dependency class holds a Gem name and a Gem::Requirement
+
+class Gem::Dependency
+
+  ##
+  # Valid dependency types.
+  #--
+  # When this list is updated, be sure to change
+  # Gem::Specification::CURRENT_SPECIFICATION_VERSION as well.
+
+  TYPES = [
+    :development,
+    :runtime,
+  ]
+
+  ##
+  # Dependency name or regular expression.
+
+  attr_accessor :name
+
+  ##
+  # Dependency type.
+
+  attr_reader :type
+
+  ##
+  # Dependent versions.
+
+  attr_writer :version_requirements
+
+  ##
+  # Orders dependencies by name only.
+
+  def <=>(other)
+    [@name] <=> [other.name]
+  end
+
+  ##
+  # Constructs a dependency with +name+ and +requirements+.
+
+  def initialize(name, version_requirements, type=:runtime)
+    @name = name
+
+    unless TYPES.include? type
+      raise ArgumentError, "Valid types are #{TYPES.inspect}, not #{@type.inspect}"
+    end
+
+    @type = type
+
+    @version_requirements = Gem::Requirement.create version_requirements
+    @version_requirement = nil   # Avoid warnings.
+  end
+
+  def version_requirements
+    normalize if defined? @version_requirement and @version_requirement
+    @version_requirements
+  end
+
+  def requirement_list
+    version_requirements.as_list
+  end
+
+  alias requirements_list requirement_list
+
+  def normalize
+    ver = @version_requirement.instance_eval { @version }
+    @version_requirements = Gem::Requirement.new([ver])
+    @version_requirement = nil
+  end
+
+  def to_s # :nodoc:
+    "#{name} (#{version_requirements}, #{@type || :runtime})"
+  end
+
+  def ==(other) # :nodoc:
+    self.class === other &&
+      self.name == other.name &&
+      self.type == other.type &&
+      self.version_requirements == other.version_requirements
+  end
+
+  ##
+  # Uses this dependency as a pattern to compare to the dependency +other+.
+  # This dependency will match if the name matches the other's name, and other
+  # has only an equal version requirement that satisfies this dependency.
+
+  def =~(other)
+    return false unless self.class === other
+
+    pattern = @name
+    pattern = /\A#{@name}\Z/ unless Regexp === pattern
+
+    return false unless pattern =~ other.name
+
+    reqs = other.version_requirements.requirements
+
+    return false unless reqs.length == 1
+    return false unless reqs.first.first == '='
+
+    version = reqs.first.last
+
+    version_requirements.satisfied_by? version
+  end
+
+  def hash # :nodoc:
+    name.hash + type.hash + version_requirements.hash
+  end
+
+end
+