Use inherited documentation when checking alias parameter coverage

lib/rdoc/stats.rb

@@ -468,7 +468,16 @@ def undoc_params(method)
 
     return 0, [] if params.empty?
 
-    document = parse method.comment
+    comment = method.comment
+
+    if comment.empty?
+      # An alias, or a method with a #see target, carries no comment of its
+      # own but inherits the documentation RDoc::MethodAttr#documented? uses.
+      inherited = method.is_alias_for || method.see
+      comment = inherited.comment if inherited
+    end
+
+    document = parse comment
 
     tts = document.accept @formatter
 

test/rdoc/rdoc_stats_test.rb

@@ -664,6 +664,21 @@ def test_undoc_params
     assert_equal %w[a], undoc
   end
 
+  def test_undoc_params_alias
+    method = RDoc::AnyMethod.new 'm'
+    method.params = '(a)'
+    method.comment = comment '+a+'
+
+    aliased = RDoc::AnyMethod.new 'n'
+    aliased.params = '(a)'
+    aliased.is_alias_for = method
+
+    total, undoc = @s.undoc_params aliased
+
+    assert_equal 1, total
+    assert_empty    undoc
+  end
+
   def test_undoc_params_block
     method = RDoc::AnyMethod.new 'm'
     method.params = '(&a)'