Add AvailableAttr::isLanguageVersionSpecific

Author: graydon

include/swift/AST/Attr.h

@@ -625,6 +625,9 @@ class AvailableAttr : public DeclAttribute {
   /// The platform of the availability.
   const PlatformKind Platform;
 
+  /// Whether this is a language-version-specific entity.
+  bool isLanguageVersionSpecific() const;
+
   /// Whether this is an unconditionally unavailable entity.
   bool isUnconditionallyUnavailable() const;
 

lib/AST/Attr.cpp

@@ -667,6 +667,19 @@ bool AvailableAttr::isActivePlatform(const ASTContext &ctx) const {
   return isPlatformActive(Platform, ctx.LangOpts);
 }
 
+bool AvailableAttr::isLanguageVersionSpecific() const {
+  if (PlatformAgnostic ==
+      PlatformAgnosticAvailabilityKind::SwiftVersionSpecific)
+    {
+      assert(Platform == PlatformKind::none &&
+             (Introduced.hasValue() ||
+              Deprecated.hasValue() ||
+              Obsoleted.hasValue()));
+      return true;
+    }
+  return false;
+}
+
 bool AvailableAttr::isUnconditionallyUnavailable() const {
   switch (PlatformAgnostic) {
   case PlatformAgnosticAvailabilityKind::None: