1 files changed, 23 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/type/hash_lookup_type_map.rb b/activemodel/lib/active_model/type/hash_lookup_type_map.rb
new file mode 100644
index 0000000000..45d3515aad
--- /dev/null
+++ b/activemodel/lib/active_model/type/hash_lookup_type_map.rb
@@ -0,0 +1,23 @@
+module ActiveModel
+  module Type
+    class HashLookupTypeMap < TypeMap # :nodoc:
+      def alias_type(type, alias_type)
+        register_type(type) { |_, *args| lookup(alias_type, *args) }
+      end
+
+      def key?(key)
+        @mapping.key?(key)
+      end
+
+      def keys
+        @mapping.keys
+      end
+
+      private
+
+      def perform_fetch(type, *args, &block)
+        @mapping.fetch(type, block).call(type, *args)
+      end
+    end
+  end
+end