Address review feedback

Rename getDefaultArgumentInitContextCached,
and have it return an Optional<Initializer *>.

Author: hamishknight

include/swift/AST/Decl.h

@@ -5198,7 +5198,7 @@ class ParamDecl : public VarDecl {
 
   /// Retrieve the cached initializer context for the parameter's default
   /// argument without triggering a request.
-  Initializer *getDefaultArgumentInitContextCached() const;
+  Optional<Initializer *> getCachedDefaultArgumentInitContext() const;
 
   enum class Flags : uint8_t {
     /// Whether or not this parameter is vargs.

lib/AST/Decl.cpp

@@ -6046,11 +6046,12 @@ AnyFunctionType::Param ParamDecl::toFunctionParam(Type type) const {
   return AnyFunctionType::Param(type, label, flags);
 }
 
-Initializer *ParamDecl::getDefaultArgumentInitContextCached() const {
+Optional<Initializer *> ParamDecl::getCachedDefaultArgumentInitContext() const {
   if (auto *defaultInfo = DefaultValueAndFlags.getPointer())
-      return defaultInfo->InitContextAndIsTypeChecked.getPointer();
+    if (auto *init = defaultInfo->InitContextAndIsTypeChecked.getPointer())
+      return init;
 
-  return nullptr;
+  return None;
 }
 
 Initializer *ParamDecl::getDefaultArgumentInitContext() const {
@@ -6160,7 +6161,7 @@ CustomAttr *ValueDecl::getAttachedFunctionBuilder() const {
 }
 
 void ParamDecl::setDefaultArgumentInitContext(Initializer *initContext) {
-  auto *oldContext = getDefaultArgumentInitContextCached();
+  auto oldContext = getCachedDefaultArgumentInitContext();
   assert((!oldContext || oldContext == initContext) &&
          "Cannot change init context after setting");
 

lib/AST/TypeCheckRequests.cpp

@@ -1190,10 +1190,7 @@ void HasCircularRawValueRequest::noteCycleStep(DiagnosticEngine &diags) const {
 Optional<Initializer *>
 DefaultArgumentInitContextRequest::getCachedResult() const {
   auto *param = std::get<0>(getStorage());
-  if (auto *init = param->getDefaultArgumentInitContextCached())
-    return init;
-
-  return None;
+  return param->getCachedDefaultArgumentInitContext();
 }
 
 void DefaultArgumentInitContextRequest::cacheResult(Initializer *init) const {

lib/Sema/TypeCheckDecl.cpp

@@ -2066,7 +2066,7 @@ DefaultArgumentInitContextRequest::evaluate(Evaluator &eval,
       continue;
 
     // If this param already has a context, continue using it.
-    if (otherParam->getDefaultArgumentInitContextCached())
+    if (otherParam->getCachedDefaultArgumentInitContext())
       continue;
 
     // Create a new initializer context. If this is for the parameter that