RewriteFilterBehavior::rewriteCondition() Argument and return type do not match

[lippserd]

RewriteFilterBehavior::rewriteCondition() expects Filter\Condition but allows Filter\Rule to be returned. This can also return Chain, such as in FlattenedObjectVars. This breaks any behavior that follows a behavior that returns something other than Filter\Condition, as behaviors are processed sequentially, using the previous behavior's result for the current one.