1 files changed, 39 insertions, 0 deletions
diff --git a/lib/rubygems/source/installed.rb b/lib/rubygems/source/installed.rb
new file mode 100644
index 0000000000..f5c96fee51
--- /dev/null
+++ b/lib/rubygems/source/installed.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+##
+# Represents an installed gem.  This is used for dependency resolution.
+
+class Gem::Source::Installed < Gem::Source
+  def initialize # :nodoc:
+    @uri = nil
+  end
+
+  ##
+  # Installed sources sort before all other sources
+
+  def <=>(other)
+    case other
+    when Gem::Source::Git,
+         Gem::Source::Lock,
+         Gem::Source::Vendor then
+      -1
+    when Gem::Source::Installed then
+      0
+    when Gem::Source then
+      1
+    end
+  end
+
+  ##
+  # We don't need to download an installed gem
+
+  def download(spec, path)
+    nil
+  end
+
+  def pretty_print(q) # :nodoc:
+    q.object_group(self) do
+      q.text "[Installed]"
+    end
+  end
+end