That works fine.  The ReturnTypeAsserter I'm using to just process a single function.  I don't want it to walk into nested functions and modify their return expressions with the enclosing function's return type.  The nested function gets handled when TypeTransformer visits the nested.  I was modeling it after like the AlphaRenamer.  Would a different name make it more clear that it's not a normal transformer added to FromOptionsTransformer?