AST: Introduce SemanticAvailableAttr::isSPI().

Author: tshortli

include/swift/AST/Attr.h

@@ -3313,6 +3313,9 @@ class SemanticAvailableAttr final {
   /// compilation context.
   bool isActive(ASTContext &ctx) const;
 
+  /// Whether this attribute was spelled `@_spi_available`.
+  bool isSPI() const { return attr->isSPI(); }
+
   bool operator==(const SemanticAvailableAttr &other) const {
     return other.attr == attr;
   }

lib/AST/Attr.cpp

@@ -421,7 +421,7 @@ void DeclAttributes::dump(const Decl *D) const {
 LLVM_READONLY
 static bool isShortAvailable(const SemanticAvailableAttr &attr) {
   auto parsedAttr = attr.getParsedAttr();
-  if (parsedAttr->isSPI())
+  if (attr.isSPI())
     return false;
 
   if (!attr.getIntroduced().has_value())

lib/AST/Availability.cpp

@@ -156,7 +156,7 @@ static void mergeWithInferredAvailability(SemanticAvailableAttr Attr,
   // The merge of two introduction versions is the maximum of the two versions.
   if (mergeIntoInferredVersion(Attr.getIntroduced(), Inferred.Introduced,
                                std::max)) {
-    Inferred.IsSPI = ParsedAttr->isSPI();
+    Inferred.IsSPI = Attr.isSPI();
   }
 
   // The merge of deprecated and obsoleted versions takes the minimum.
@@ -821,7 +821,7 @@ AvailabilityRange AvailabilityInference::availableRange(const Decl *D) {
 
 bool AvailabilityInference::isAvailableAsSPI(const Decl *D) {
   if (auto attr = D->getAvailableAttrForPlatformIntroduction())
-    return attr->getParsedAttr()->isSPI();
+    return attr->isSPI();
 
   return false;
 }