Index: doc/working/resolver_design.md
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--- doc/working/resolver_design.md	(revision 88e0080b90dabaf4c321cedeaab29b07bb4972a2)
+++ doc/working/resolver_design.md	(revision 4163409822a316e6963e427468b710d68b0213cb)
@@ -41,4 +41,13 @@
 ensure that they are two-arg functions (this restriction may be valuable 
 regardless).
+
+Regardless of syntax, there should be a type assertion that expresses `From` 
+is convertable to `To`. 
+If user-defined conversions are not added to the language, 
+`void ?{} ( To*, From )` may be a suitable representation, relying on 
+conversions on the argument types to account for transitivity. 
+On the other hand, `To*` should perhaps match its target type exactly, so 
+another assertion syntax specific to conversions may be required, e.g. 
+`From -> To`.
 
 ### Constructor Idiom ###