[NFC][RequirementMachine] Stylistic changes for computing confict

diagnostics.

Move computing requirements from rules into a static function, make
a few variables const, etc.

Author: hborla

lib/AST/RequirementMachine/RewriteSystem.cpp

@@ -753,20 +753,44 @@ void RewriteSystem::freeze() {
   ConflictingRules.clear();
 }
 
+static Optional<Requirement>
+getRequirementForDiagnostics(Type subject, Symbol property) {
+  switch (property.getKind()) {
+  case Symbol::Kind::ConcreteType:
+    return Requirement(RequirementKind::SameType, subject,
+                       property.getConcreteType());
+
+  case Symbol::Kind::Superclass:
+    return Requirement(RequirementKind::Superclass, subject,
+                       property.getConcreteType());
+
+  case Symbol::Kind::Protocol:
+    return Requirement(RequirementKind::Conformance, subject,
+                       property.getProtocol()->getDeclaredInterfaceType());
+
+  case Symbol::Kind::Layout:
+    return Requirement(RequirementKind::Layout, subject,
+                       property.getLayoutConstraint());
+
+  default:
+    return None;
+  }
+}
+
 void RewriteSystem::computeConflictDiagnostics(
     SmallVectorImpl<RequirementError> &errors, SourceLoc signatureLoc,
     const PropertyMap &propertyMap,
     TypeArrayView<GenericTypeParamType> genericParams) {
   for (auto pair : ConflictingRules) {
-    auto *firstRule = &getRule(pair.first);
-    auto *secondRule = &getRule(pair.second);
+    const auto &firstRule = getRule(pair.first);
+    const auto &secondRule = getRule(pair.second);
 
-    auto firstProperty = firstRule->isPropertyRule();
-    auto secondProperty = secondRule->isPropertyRule();
+    auto firstProperty = firstRule.isPropertyRule();
+    auto secondProperty = secondRule.isPropertyRule();
     assert(firstProperty && secondProperty);
 
-    auto firstTerm = firstRule->getRHS();
-    auto secondTerm = secondRule->getRHS();
+    auto firstTerm = firstRule.getRHS();
+    auto secondTerm = secondRule.getRHS();
     auto subjectTerm =
         firstTerm.size() > secondTerm.size() ? firstTerm : secondTerm;
 
@@ -777,8 +801,8 @@ void RewriteSystem::computeConflictDiagnostics(
 
     Type subject = propertyMap.getTypeForTerm(subjectTerm, genericParams);
     errors.push_back(RequirementError::forConflictingRequirement(
-        *firstRule->getPropertyRequirement(subject),
-        *secondRule->getPropertyRequirement(subject),
+        *getRequirementForDiagnostics(subject, *firstProperty),
+        *getRequirementForDiagnostics(subject, *secondProperty),
         signatureLoc));
   }
 }

lib/AST/RequirementMachine/Rule.cpp

@@ -43,33 +43,6 @@ Optional<Symbol> Rule::isPropertyRule() const {
   return property;
 }
 
-Optional<Requirement> Rule::getPropertyRequirement(Type subject) const {
-  auto property = isPropertyRule();
-  if (!property)
-    return None;
-
-  switch (property->getKind()) {
-  case Symbol::Kind::ConcreteType:
-    return Requirement(RequirementKind::SameType, subject,
-                       property->getConcreteType());
-
-  case Symbol::Kind::Superclass:
-    return Requirement(RequirementKind::Superclass, subject,
-                       property->getConcreteType());
-
-  case Symbol::Kind::Protocol:
-    return Requirement(RequirementKind::Conformance, subject,
-                       property->getProtocol()->getDeclaredInterfaceType());
-
-  case Symbol::Kind::Layout:
-    return Requirement(RequirementKind::Layout, subject,
-                       property->getLayoutConstraint());
-
-  default:
-    return None;
-  }
-}
-
 /// If this is a rule of the form T.[P] => T where [P] is a protocol symbol,
 /// return the protocol P, otherwise return nullptr.
 const ProtocolDecl *Rule::isProtocolConformanceRule() const {

lib/AST/RequirementMachine/Rule.h

@@ -13,8 +13,6 @@
 #ifndef SWIFT_RULE_H
 #define SWIFT_RULE_H
 
-#include "swift/AST/Requirement.h"
-
 #include "Symbol.h"
 #include "Term.h"
 
@@ -109,8 +107,6 @@ class Rule final {
 
   Optional<Symbol> isPropertyRule() const;
 
-  Optional<Requirement> getPropertyRequirement(Type subject) const;
-
   const ProtocolDecl *isProtocolConformanceRule() const;
 
   const ProtocolDecl *isAnyConformanceRule() const;