[metadata prespecialization] Available in 5.3.

Author: nate-chandler

include/swift/AST/ASTContext.h

@@ -631,6 +631,10 @@ class ASTContext final {
   /// compiler for the target platform.
   AvailabilityContext getSwift52Availability();
 
+  /// Get the runtime availability of features introduced in the Swift 5.3
+  /// compiler for the target platform.
+  AvailabilityContext getSwift53Availability();
+
   /// Get the runtime availability of features that have been introduced in the
   /// Swift compiler for future versions of the target platform.
   AvailabilityContext getSwiftFutureAvailability();

lib/AST/Availability.cpp

@@ -243,7 +243,7 @@ AvailabilityContext ASTContext::getTypesInAbstractMetadataStateAvailability() {
 }
 
 AvailabilityContext ASTContext::getPrespecializedGenericMetadataAvailability() {
-  return getSwiftFutureAvailability();
+  return getSwift53Availability();
 }
 
 AvailabilityContext ASTContext::getSwift52Availability() {
@@ -263,6 +263,23 @@ AvailabilityContext ASTContext::getSwift52Availability() {
   }
 }
 
+AvailabilityContext ASTContext::getSwift53Availability() {
+  auto target = LangOpts.Target;
+
+  if (target.isMacOSX() ) {
+    return AvailabilityContext(
+        VersionRange::allGTE(llvm::VersionTuple(10, 99, 0)));
+  } else if (target.isiOS()) {
+    return AvailabilityContext(
+        VersionRange::allGTE(llvm::VersionTuple(99, 0, 0)));
+  } else if (target.isWatchOS()) {
+    return AvailabilityContext(
+        VersionRange::allGTE(llvm::VersionTuple(9, 99, 0)));
+  } else {
+    return AvailabilityContext::alwaysAvailable();
+  }
+}
+
 AvailabilityContext ASTContext::getSwiftFutureAvailability() {
   auto target = LangOpts.Target;