railties: Move the definition of PluginGenerator#app_path to railties…

….rbs

As a preparation of ruby#693, this moves the definition of
`Rails::Generator::PluginGenerator#app_path` to railties.rbs

gems/railties/6.0/patch.rbs

@@ -1,19 +1,26 @@
-module Rails
-  module Generators
-    class PluginGenerator < AppBase
-      # It is necessary to satisfy alias target.
-      # TODO: Define this method to correct place.
-      def app_path: () -> untyped
-    end
-  end
-end
-
 # rbs gem has erb library but it doesn't have ERB::Compiler definition.
 class ERB
   class Compiler
   end
 end
 
+# Remove the fake Minitest type
+# if the real type of Minitest is available
+module Minitest
+  class SummaryReporter
+  end
+
+  class StatisticsReporter
+  end
+end
+
+# Remove the fake Rack type
+# if the real type of Minitest is available
+module Rack
+  class Server
+  end
+end
+
 # Remove the fake RDoc type
 # if the real type of Minitest is available
 module RDoc
@@ -25,3 +32,15 @@ module RDoc
   class Task
   end
 end
+
+# Remove the fake types for Gem::Version
+# if the real types are available.
+module Gem
+  class Version
+  end
+end
+
+# Remove the fake types for FileUtils
+# if the real types are available.
+module FileUtils
+end

gems/railties/6.0/railties.rbs

@@ -0,0 +1,9 @@
+module Rails
+  module Generators
+    class PluginGenerator < AppBase
+      # It is necessary to satisfy alias target.
+      # TODO: Define this method to correct place.
+      def app_path: () -> untyped
+    end
+  end
+end