thread optimisation obligations through rewrite passes

test/invariants.ml

@@ -18,6 +18,9 @@ let find_case name =
   | Some case -> case
   | None -> failwith ("missing case " ^ name)
 
+let has_obligation kind obligations =
+  List.exists (fun (o : Pipeline.obligation) -> o.kind = kind) obligations
+
 let () =
   List.iter
     (fun (case : Corpus.case) ->
@@ -33,6 +36,16 @@ let () =
   assert_true
     "expected representation exposure witness"
     (repr.failure_mode = Audit.Representation_exposure);
+  assert_true
+    "expected unsafe inlining to emit representation exposure obligation"
+    (has_obligation Pipeline.Exposed_representation repr.compiled.obligations);
+  let safe = Audit.audit_case (find_case "safe-polymorphic-instantiation") in
+  assert_true
+    "safe instantiation should not emit representation exposure obligation"
+    (not (has_obligation Pipeline.Exposed_representation safe.compiled.obligations));
+  assert_true
+    "safe instantiation should emit preserve relation obligations at rewrite sites"
+    (has_obligation Pipeline.Preserve_relation safe.compiled.obligations);
   let strict = Audit.audit_case (find_case "strictness-induced-termination-change") in
   assert_true
     "expected strictness shift witness"