wmllint: warn about [filter] in [kill] tags

changelog.md

@@ -13,6 +13,7 @@
  ### User interface
  ### WML Engine
  ### Miscellaneous and Bug Fixes
+   * wmllint now warns about `[kill]` tags containing `[filter]` tags
 
 ## Version 1.17.24
  ### Campaigns

data/tools/wmllint

@@ -1393,6 +1393,9 @@ def validate_on_pop(tagstack, closer, filename, lineno):
     if closer == "variation" and "variation_id" not in attributes:
         print('"%s", line %d: [variation] is missing required variation_id attribute' % \
               (filename, lineno))
+    if closer == "filter" and "kill" in ancestors:
+        print('"%s", line %d: [kill] should have an inline StandardUnitFilter instead of using [filter]' % \
+              (filename, lineno))
 
 def within(tag):
     "Did the specified tag lead one of our enclosing contexts?"