Merge pull request swiftlang#71225 from tshortli/back-deployed-attr-refactor

AST/Sema: Adjust `@backDeployed` attribute diagnostics for unavailable decls

Author: tshortli

include/swift/AST/PlatformKind.h

@@ -51,6 +51,12 @@ llvm::Optional<StringRef> closestCorrectedPlatformString(StringRef candidate);
 /// for emission in diagnostics (e.g., "macOS").
 StringRef prettyPlatformString(PlatformKind platform);
 
+/// Returns the base platform for an application-extension platform. For example
+/// `iOS` would be returned for `iOSApplicationExtension`. Returns `None` for
+/// platforms which are not application extension platforms.
+llvm::Optional<PlatformKind>
+basePlatformForExtensionPlatform(PlatformKind Platform);
+
 /// Returns whether the passed-in platform is active, given the language
 /// options. A platform is active if either it is the target platform or its
 /// AppExtension variant is the target platform. For example, OS X is

lib/AST/Decl.cpp

@@ -551,8 +551,10 @@ Decl::getIntroducedOSVersion(PlatformKind Kind) const {
 
 llvm::Optional<llvm::VersionTuple>
 Decl::getBackDeployedBeforeOSVersion(ASTContext &Ctx) const {
-  if (auto *attr = getAttrs().getBackDeployed(Ctx))
-    return attr->Version;
+  if (auto *attr = getAttrs().getBackDeployed(Ctx)) {
+    auto version = attr->Version;
+    return version;
+  }
 
   // Accessors may inherit `@backDeployed`.
   if (auto *AD = dyn_cast<AccessorDecl>(this))

lib/AST/PlatformKind.cpp

@@ -83,14 +83,19 @@ swift::closestCorrectedPlatformString(StringRef candidate) {
   return (minDistance < distanceThreshold) ? result : llvm::None;
 }
 
-static bool isApplicationExtensionPlatform(PlatformKind Platform) {
+llvm::Optional<PlatformKind>
+swift::basePlatformForExtensionPlatform(PlatformKind Platform) {
   switch (Platform) {
   case PlatformKind::macOSApplicationExtension:
+    return PlatformKind::macOS;
   case PlatformKind::iOSApplicationExtension:
+    return PlatformKind::iOS;
   case PlatformKind::macCatalystApplicationExtension:
+    return PlatformKind::macCatalyst;
   case PlatformKind::tvOSApplicationExtension:
+    return PlatformKind::tvOS;
   case PlatformKind::watchOSApplicationExtension:
-    return true;
+    return PlatformKind::watchOS;
   case PlatformKind::macOS:
   case PlatformKind::iOS:
   case PlatformKind::macCatalyst:
@@ -99,11 +104,15 @@ static bool isApplicationExtensionPlatform(PlatformKind Platform) {
   case PlatformKind::OpenBSD:
   case PlatformKind::Windows:
   case PlatformKind::none:
-    return false;
+    return llvm::None;
   }
   llvm_unreachable("bad PlatformKind");
 }
 
+static bool isApplicationExtensionPlatform(PlatformKind Platform) {
+  return basePlatformForExtensionPlatform(Platform).has_value();
+}
+
 static bool isPlatformActiveForTarget(PlatformKind Platform,
                                       const llvm::Triple &Target,
                                       bool EnableAppExtensionRestrictions) {
@@ -187,20 +196,21 @@ PlatformKind swift::targetPlatform(const LangOptions &LangOpts) {
 
 bool swift::inheritsAvailabilityFromPlatform(PlatformKind Child,
                                              PlatformKind Parent) {
+  if (auto ChildPlatformBase = basePlatformForExtensionPlatform(Child)) {
+    if (Parent == ChildPlatformBase)
+      return true;
+  }
+
   if (Child == PlatformKind::macCatalyst && Parent == PlatformKind::iOS)
     return true;
 
   if (Child == PlatformKind::macCatalystApplicationExtension) {
     if (Parent == PlatformKind::iOS ||
-        Parent == PlatformKind::iOSApplicationExtension ||
-        Parent == PlatformKind::macCatalyst) {
+        Parent == PlatformKind::iOSApplicationExtension) {
       return true;
     }
   }
 
-  // Ideally we would have all ApplicationExtension platforms
-  // inherit from their non-extension platform.
-
   return false;
 }
 

lib/Sema/TypeCheckAttr.cpp

@@ -4547,11 +4547,12 @@ void AttributeChecker::checkBackDeployedAttrs(
     // Unavailable decls cannot be back deployed.
     if (auto unavailableAttrPair = VD->getSemanticUnavailableAttr()) {
       auto unavailableAttr = unavailableAttrPair.value().first;
+      if (!inheritsAvailabilityFromPlatform(unavailableAttr->Platform,
+                                            Attr->Platform)) {
+        auto platformString = prettyPlatformString(Attr->Platform);
 
-      if (unavailableAttr->Platform == PlatformKind::none ||
-          unavailableAttr->Platform == Attr->Platform) {
-        diagnose(AtLoc, diag::attr_has_no_effect_on_unavailable_decl, Attr,
-                 VD, prettyPlatformString(Platform));
+        diagnose(AtLoc, diag::attr_has_no_effect_on_unavailable_decl, Attr, VD,
+                 platformString);
         diagnose(unavailableAttr->AtLoc, diag::availability_marked_unavailable,
                  VD)
             .highlight(unavailableAttr->getRange());
@@ -4563,14 +4564,17 @@ void AttributeChecker::checkBackDeployedAttrs(
     // If it's not, the attribute doesn't make sense since the back deployment
     // fallback could never be executed at runtime.
     if (auto availableRangeAttrPair = VD->getSemanticAvailableRangeAttr()) {
+      auto beforePlatformString = prettyPlatformString(Attr->Platform);
+      auto beforeVersion = Attr->Version;
       auto availableAttr = availableRangeAttrPair.value().first;
-      if (Attr->Version <= availableAttr->Introduced.value()) {
+      auto introVersion = availableAttr->Introduced.value();
+      StringRef introPlatformString = availableAttr->prettyPlatformString();
+
+      if (Attr->Version <= introVersion) {
         diagnose(AtLoc, diag::attr_has_no_effect_decl_not_available_before,
-                 Attr, VD, prettyPlatformString(Platform),
-                 Attr->Version);
+                 Attr, VD, beforePlatformString, beforeVersion);
         diagnose(availableAttr->AtLoc, diag::availability_introduced_in_version,
-                 VD, prettyPlatformString(availableAttr->Platform),
-                 *availableAttr->Introduced)
+                 VD, introPlatformString, introVersion)
             .highlight(availableAttr->getRange());
         continue;
       }

test/attr/attr_availability_transitive_ios_appext.swift

@@ -8,7 +8,7 @@
 func ios() {} // expected-note 2{{'ios()' has been explicitly marked unavailable here}}
 
 @available(iOSApplicationExtension, unavailable)
-func ios_extension() {} // expected-note 2{{'ios_extension()' has been explicitly marked unavailable here}}
+func ios_extension() {} // expected-note {{'ios_extension()' has been explicitly marked unavailable here}}
 
 func call_ios_extension() {
     ios_extension() // expected-error {{'ios_extension()' is unavailable}}
@@ -19,7 +19,7 @@ func call_ios() {
 
 @available(iOS, unavailable)
 func ios_call_ios_extension() {
-    ios_extension() // expected-error {{'ios_extension()' is unavailable}}
+    ios_extension()
 }
 
 @available(iOS, unavailable)

test/attr/attr_availability_transitive_osx_appext.swift

@@ -7,7 +7,7 @@
 func osx() {} // expected-note 3{{'osx()' has been explicitly marked unavailable here}}
 
 @available(OSXApplicationExtension, unavailable)
-func osx_extension() {} // expected-note 3{{'osx_extension()' has been explicitly marked unavailable here}}
+func osx_extension() {} // expected-note {{'osx_extension()' has been explicitly marked unavailable here}}
 
 func call_osx_extension() {
     osx_extension() // expected-error {{'osx_extension()' is unavailable}}
@@ -18,7 +18,7 @@ func call_osx() {
 
 @available(OSX, unavailable)
 func osx_call_osx_extension() {
-    osx_extension() // expected-error {{'osx_extension()' is unavailable}}
+    osx_extension()
 }
 
 @available(OSX, unavailable)
@@ -46,7 +46,7 @@ extension NotOnOSX {
   }
 
   func osx_call_osx_extension() {
-    osx_extension() // expected-error {{'osx_extension()' is unavailable in application extensions for macOS}}
+    osx_extension()
   }
 }