Warned about passing -allinst

changelog.dd

@@ -559,7 +559,7 @@ The class could also be implemented in another library for which you do not have
 which means you wouldn't be able to edit the inheritance list of that class.)
 
 $(P The new $(D wrap) function allows you to perform a $(I structural cast), allowing a class object to
-act as if it were an object of another type. For example:)
+act as if it were an object of another type. For example (note: for now please pass the -allinst flag to dmd when compiling):)
 
 ---------
 import std.typecons;