RequirementMachine: Stub out logic for property map to record rewrite loops

For homotopy reduction to properly deal with new rules introduced
while bulding the property map, rewrite loops must be recorded
relating these to existing rules.

lib/AST/RequirementMachine/PropertyMap.cpp

@@ -311,7 +311,7 @@ void PropertyMap::clear() {
 /// key. Must be called in monotonically non-decreasing key order.
 void PropertyMap::addProperty(
     Term key, Symbol property, unsigned ruleID,
-    SmallVectorImpl<std::pair<MutableTerm, MutableTerm>> &inducedRules) {
+    SmallVectorImpl<InducedRule> &inducedRules) {
   assert(property.isProperty());
   assert(*System.getRule(ruleID).isPropertyRule() == property);
   auto *props = getOrCreateProperties(key);
@@ -371,7 +371,7 @@ PropertyMap::buildPropertyMap(unsigned maxIterations,
 
   // Merging multiple superclass or concrete type rules can induce new rules
   // to unify concrete type constructor arguments.
-  SmallVector<std::pair<MutableTerm, MutableTerm>, 3> inducedRules;
+  SmallVector<InducedRule, 3> inducedRules;
 
   for (const auto &bucket : properties) {
     for (auto property : bucket) {
@@ -392,7 +392,9 @@ PropertyMap::buildPropertyMap(unsigned maxIterations,
   // where the left hand side is not already equivalent to the right hand side.
   unsigned addedNewRules = 0;
   for (auto pair : inducedRules) {
-    if (System.addRule(pair.first, pair.second)) {
+    // FIXME: Eventually, all induced rules will have a rewrite path.
+    if (System.addRule(pair.LHS, pair.RHS,
+                       pair.Path.empty() ? nullptr : &pair.Path)) {
       ++addedNewRules;
 
       const auto &newRule = System.getRules().back();