do a hash lookup for collision detection

hash lookup should be faster than searching an array.

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -1765,7 +1765,7 @@ def name_for_action(as, action) #:nodoc:
               # and return nil in case it isn't. Otherwise, we pass the invalid name
               # forward so the underlying router engine treats it and raises an exception.
               if as.nil?
-                candidate unless @set.routes.find { |r| r.name == candidate } || candidate !~ /\A[_a-z]/i
+                candidate unless @set.named_routes.key?(candidate) || candidate !~ /\A[_a-z]/i
               else
                 candidate
               end

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -140,6 +140,10 @@ def get(name)
           routes[name.to_sym]
         end
 
+        def key?(name)
+          routes.key? name.to_sym
+        end
+
         alias []=   add
         alias []    get
         alias clear clear!