RequirementMachine: Factor out Rule::isPropertyRule() from the property map

Author: slavapestov

lib/AST/RequirementMachine/PropertyMap.cpp

@@ -1043,23 +1043,16 @@ RewriteSystem::buildPropertyMap(PropertyMap &map,
     if (rule.isDeleted())
       continue;
 
-    auto lhs = rule.getLHS();
-    auto rhs = rule.getRHS();
-
     // Collect all rules of the form T.[p] => T where T is canonical.
-    auto property = lhs.back();
-    if (!property.isProperty())
-      continue;
-
-    if (lhs.size() - 1 != rhs.size())
+    auto property = rule.isPropertyRule();
+    if (!property)
       continue;
 
-    if (!std::equal(rhs.begin(), rhs.end(), lhs.begin()))
-      continue;
-
-    if (rhs.size() >= properties.size())
-      properties.resize(rhs.size() + 1);
-    properties[rhs.size()].emplace_back(rhs, property);
+    auto rhs = rule.getRHS();
+    unsigned length = rhs.size();
+    if (length >= properties.size())
+      properties.resize(length + 1);
+    properties[length].emplace_back(rhs, *property);
   }
 
   // Merging multiple superclass or concrete type rules can induce new rules

lib/AST/RequirementMachine/RewriteSystem.cpp

@@ -23,6 +23,28 @@
 using namespace swift;
 using namespace rewriting;
 
+Optional<Symbol> Rule::isPropertyRule() const {
+  auto property = LHS.back();
+
+  if (!property.isProperty())
+    return None;
+
+  if (LHS.size() - 1 != RHS.size())
+    return None;
+
+  if (!std::equal(RHS.begin(), RHS.end(), LHS.begin()))
+    return None;
+
+  return property;
+}
+
+bool Rule::isProtocolConformanceRule() const {
+  if (auto property = isPropertyRule())
+    return property->getKind() == Symbol::Kind::Protocol;
+
+  return false;
+}
+
 void Rule::dump(llvm::raw_ostream &out) const {
   out << LHS << " => " << RHS;
   if (deleted)

lib/AST/RequirementMachine/RewriteSystem.h

@@ -50,6 +50,10 @@ class Rule final {
   const Term &getLHS() const { return LHS; }
   const Term &getRHS() const { return RHS; }
 
+  Optional<Symbol> isPropertyRule() const;
+
+  bool isProtocolConformanceRule() const;
+
   /// Returns if the rule was deleted.
   bool isDeleted() const {
     return deleted;