Fix error when Bundler installation is corrupted

bundler/lib/bundler/errors.rb

@@ -230,4 +230,18 @@ def message
 
     status_code(38)
   end
+
+  class CorruptBundlerInstallError < BundlerError
+    def initialize(loaded_spec)
+      @loaded_spec = loaded_spec
+    end
+
+    def message
+      "The running version of Bundler (#{Bundler::VERSION}) does not match the version of the specification installed for it (#{@loaded_spec.version}). " \
+      "This can be caused by reinstalling Ruby without removing previous installation, leaving around an upgraded default version of Bundler. " \
+      "Reinstalling Ruby from scratch should fix the problem."
+    end
+
+    status_code(39)
+  end
 end

bundler/lib/bundler/source/metadata.rb

@@ -11,6 +11,8 @@ def specs
           end
 
           if local_spec = Gem.loaded_specs["bundler"]
+            raise CorruptBundlerInstallError.new(local_spec) if local_spec.version.to_s != Bundler::VERSION
+
             idx << local_spec
           else
             idx << Gem::Specification.new do |s|

bundler/spec/commands/install_spec.rb

@@ -1407,4 +1407,33 @@ def run
       expect(bundled_app(".bundle/config")).not_to exist
     end
   end
+
+  context "when bundler installation is corrupt" do
+    before do
+      system_gems "bundler-9.99.8"
+
+      replace_version_file("9.99.9", dir: system_gem_path("gems/bundler-9.99.8"))
+    end
+
+    it "shows a proper error" do
+      lockfile <<~L
+        GEM
+          remote: #{file_uri_for(gem_repo1)}/
+          specs:
+
+        PLATFORMS
+          #{lockfile_platforms}
+
+        DEPENDENCIES
+
+        BUNDLED WITH
+           9.99.8
+      L
+
+      install_gemfile "source \"#{file_uri_for(gem_repo1)}\"", env: { "BUNDLER_VERSION" => "9.99.8" }, raise_on_error: false
+
+      expect(err).not_to include("ERROR REPORT TEMPLATE")
+      expect(err).to include("The running version of Bundler (9.99.9) does not match the version of the specification installed for it (9.99.8)")
+    end
+  end
 end