3 files changed, 18 insertions, 4 deletions
diff --git a/actionpack/lib/action_dispatch/routing/inspector.rb b/actionpack/lib/action_dispatch/routing/inspector.rb
index 6f651a5689..5d30a545a2 100644
--- a/actionpack/lib/action_dispatch/routing/inspector.rb
+++ b/actionpack/lib/action_dispatch/routing/inspector.rb
@@ -51,7 +51,7 @@ module ActionDispatch
 
     ##
     # This class is just used for displaying route information when someone
-    # executes `rake routes` or looks at the RoutingError page.
+    # executes `rails routes` or looks at the RoutingError page.
     # People should not use this class.
     class RoutesInspector # :nodoc:
       def initialize(routes)
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 16b430c36e..ffd5b83ad3 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -1,4 +1,3 @@
-require 'active_support/core_ext/hash/reverse_merge'
 require 'active_support/core_ext/hash/slice'
 require 'active_support/core_ext/enumerable'
 require 'active_support/core_ext/array/extract_options'
@@ -824,7 +823,7 @@ module ActionDispatch
               URL_OPTIONS.include?(k) && (v.is_a?(String) || v.is_a?(Fixnum))
             end
 
-            (options[:defaults] ||= {}).reverse_merge!(defaults)
+            options[:defaults] = defaults.merge(options[:defaults] || {})
           else
             block, options[:constraints] = options[:constraints], {}
           end
@@ -1598,7 +1597,7 @@ module ActionDispatch
             route_options = options.dup
             if _path && option_path
               ActiveSupport::Deprecation.warn <<-eowarn
-Specifying strings for both :path and the route path is deprecated.  Change things like this:
+Specifying strings for both :path and the route path is deprecated. Change things like this:
 
   match #{_path.inspect}, :path => #{option_path.inspect}
 
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 310e98f584..16237bd564 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -513,6 +513,21 @@ module ActionDispatch
 
         route = @set.add_route(name, mapping)
         named_routes[name] = route if name
+
+        if route.segment_keys.include?(:controller)
+          ActiveSupport::Deprecation.warn(<<-MSG.squish)
+            Using a dynamic :controller segment in a route is deprecated and
+            will be removed in Rails 5.1.
+          MSG
+        end
+
+        if route.segment_keys.include?(:action)
+          ActiveSupport::Deprecation.warn(<<-MSG.squish)
+            Using a dynamic :action segment in a route is deprecated and
+            will be removed in Rails 5.1.
+          MSG
+        end
+
         route
       end