check both HashNode and KeywordHashNode

lib/prism_ext.rb

@@ -104,7 +104,7 @@ def to_value
 
     # Respond key value and source for hash node
     def method_missing(method_name, *args, &block)
-      return super unless is_a?(HashNode)
+      return super unless respond_to_elements?
 
       if method_name.to_s.end_with?('_element')
         key = method_name.to_s[0..-9]
@@ -121,7 +121,7 @@ def method_missing(method_name, *args, &block)
     end
 
     def respond_to_missing?(method_name, *args)
-      return super unless is_a?(HashNode)
+      return super unless respond_to_elements?
 
       if method_name.to_s.end_with?('_element')
         key = method_name.to_s[0..-9]
@@ -136,5 +136,11 @@ def respond_to_missing?(method_name, *args)
 
       super
     end
+
+    private
+
+    def respond_to_elements?
+      is_a?(HashNode) || is_a?(KeywordHashNode)
+    end
   end
 end