[AST] NFC: Fold PackConformance::isInvalid into ProtocolConformanceRef::isInvalid

Instead of making callers responsible for that (like in other cases),
let's fold the code check `isInvalid` to make mistakes less likely.

Author: xedin

include/swift/AST/ProtocolConformanceRef.h

@@ -89,9 +89,7 @@ class ProtocolConformanceRef {
   static ProtocolConformanceRef forMissingOrInvalid(
       Type type, ProtocolDecl *proto);
 
-  bool isInvalid() const {
-    return !Union;
-  }
+  bool isInvalid() const;
 
   explicit operator bool() const { return !isInvalid(); }
 

lib/AST/Module.cpp

@@ -1827,11 +1827,8 @@ static ProtocolConformanceRef getPackTypeConformance(
     patternConformances.push_back(patternConformance);
   }
 
-  auto *conformance = PackConformance::get(type, protocol, patternConformances);
-  if (conformance->isInvalid())
-    return ProtocolConformanceRef::forInvalid();
-
-  return ProtocolConformanceRef(conformance);
+  return ProtocolConformanceRef(
+      PackConformance::get(type, protocol, patternConformances));
 }
 
 ProtocolConformanceRef

lib/AST/PackConformance.cpp

@@ -249,9 +249,6 @@ PackConformance::subst(InFlightSubstitution &IFS) const {
 
   auto substConformance = PackConformance::get(substConformingType, Protocol,
                                                expander.substConformances);
-  if (substConformance->isInvalid())
-    return ProtocolConformanceRef::forInvalid();
-
   return ProtocolConformanceRef(substConformance);
 }
 

lib/AST/ProtocolConformanceRef.cpp

@@ -42,6 +42,16 @@ ProtocolConformanceRef::ProtocolConformanceRef(ProtocolDecl *protocol,
   }
 }
 
+bool ProtocolConformanceRef::isInvalid() const {
+  if (!Union)
+    return true;
+
+  if (auto pack = Union.dyn_cast<PackConformance *>())
+    return pack->isInvalid();
+
+  return false;
+}
+
 ProtocolDecl *ProtocolConformanceRef::getRequirement() const {
   assert(!isInvalid());