AST: Canonicalize platform versions for @backDeployed attrs.

Also, diagnose invalid platform versions.

Part of rdar://155558161.

Author: tshortli

include/swift/AST/Attr.h

@@ -2939,17 +2939,25 @@ class UnavailableFromAsyncAttr : public DeclAttribute {
 /// available for back deployment to older OSes via emission into the client
 /// binary.
 class BackDeployedAttr : public DeclAttribute {
+  const PlatformKind Platform;
+  const llvm::VersionTuple Version;
+
 public:
   BackDeployedAttr(SourceLoc AtLoc, SourceRange Range, PlatformKind Platform,
                    const llvm::VersionTuple &Version, bool Implicit)
       : DeclAttribute(DeclAttrKind::BackDeployed, AtLoc, Range, Implicit),
         Platform(Platform), Version(Version) {}
 
   /// The platform the decl is available for back deployment in.
-  const PlatformKind Platform;
+  PlatformKind getPlatform() const { return Platform; }
 
-  /// The earliest platform version that may use the back deployed implementation.
-  const llvm::VersionTuple Version;
+  /// The `before:` version tuple that was written in source.
+  llvm::VersionTuple getParsedVersion() const { return Version; }
+
+  /// The `before:` version, which is the earliest platform version that may use
+  /// the back deployed implementation. This may be different from the version
+  /// that was written in source due to canonicalization.
+  llvm::VersionTuple getVersion() const;
 
   /// Returns true if this attribute is active given the current platform.
   bool isActivePlatform(const ASTContext &ctx, bool forTargetVariant) const;

lib/AST/ASTDumper.cpp

@@ -5121,9 +5121,10 @@ class PrintAttribute : public AttributeVisitor<PrintAttribute, void, Label>,
   }
   void visitBackDeployedAttr(BackDeployedAttr *Attr, Label label) {
     printCommon(Attr, "back_deployed_attr", label);
-    printField(Attr->Platform, Label::always("platform"));
-    printFieldRaw([&](auto &out) { out << Attr->Version.getAsString(); },
-                  Label::always("version"));
+    printField(Attr->getPlatform(), Label::always("platform"));
+    printFieldRaw(
+        [&](auto &out) { out << Attr->getParsedVersion().getAsString(); },
+        Label::always("version"));
     printFoot();
   }
   void visitCDeclAttr(CDeclAttr *Attr, Label label) {

lib/AST/Attr.cpp

@@ -421,8 +421,9 @@ DeclAttributes::getBackDeployed(const ASTContext &ctx,
 
     // We have an attribute that is active for the platform, but
     // is it more specific than our current best?
-    if (!bestAttr || inheritsAvailabilityFromPlatform(
-                         backDeployedAttr->Platform, bestAttr->Platform)) {
+    if (!bestAttr ||
+        inheritsAvailabilityFromPlatform(backDeployedAttr->getPlatform(),
+                                         bestAttr->getPlatform())) {
       bestAttr = backDeployedAttr;
     }
   }
@@ -557,8 +558,8 @@ static void printShortFormBackDeployed(ArrayRef<const DeclAttribute *> Attrs,
     if (!isFirst)
       Printer << ", ";
     auto *attr = cast<BackDeployedAttr>(DA);
-    Printer << platformString(attr->Platform) << " "
-            << attr->Version.getAsString();
+    Printer << platformString(attr->getPlatform()) << " "
+            << attr->getVersion().getAsString();
     isFirst = false;
   }
   Printer << ")";
@@ -771,7 +772,7 @@ static std::optional<PlatformKind> referencedPlatform(const DeclAttribute *attr,
     }
     return std::nullopt;
   case DeclAttrKind::BackDeployed:
-    return static_cast<const BackDeployedAttr *>(attr)->Platform;
+    return static_cast<const BackDeployedAttr *>(attr)->getPlatform();
   case DeclAttrKind::OriginallyDefinedIn:
     return static_cast<const OriginallyDefinedInAttr *>(attr)->getPlatform();
   default:
@@ -1519,8 +1520,8 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
     Printer.printAttrName("@backDeployed");
     Printer << "(before: ";
     auto Attr = cast<BackDeployedAttr>(this);
-    Printer << platformString(Attr->Platform) << " " <<
-      Attr->Version.getAsString();
+    Printer << platformString(Attr->getPlatform()) << " "
+            << Attr->getVersion().getAsString();
     Printer << ")";
     break;
   }
@@ -2350,6 +2351,10 @@ AvailableAttr *AvailableAttr::createUnavailableInEmbedded(ASTContext &C,
       /*Implicit=*/false, /*IsSPI=*/false);
 }
 
+llvm::VersionTuple BackDeployedAttr::getVersion() const {
+  return canonicalizePlatformVersion(getPlatform(), getParsedVersion());
+}
+
 bool BackDeployedAttr::isActivePlatform(const ASTContext &ctx,
                                         bool forTargetVariant) const {
   return isPlatformActive(Platform, ctx.LangOpts, forTargetVariant);

lib/AST/Availability.cpp

@@ -370,7 +370,7 @@ bool AvailabilityInference::updateBeforeAvailabilityDomainForFallback(
   if (!hasRemap)
     return false;
 
-  auto beforeVersion = attr->Version;
+  auto beforeVersion = attr->getVersion();
   auto potentiallyRemappedIntroducedVersion =
       getRemappedIntroducedVersionForFallbackPlatform(ctx, beforeVersion);
   if (potentiallyRemappedIntroducedVersion.has_value()) {

lib/AST/Decl.cpp

@@ -611,7 +611,7 @@ std::optional<std::pair<const BackDeployedAttr *, AvailabilityRange>>
 Decl::getBackDeployedAttrAndRange(ASTContext &Ctx,
                                   bool forTargetVariant) const {
   if (auto *attr = getAttrs().getBackDeployed(Ctx, forTargetVariant)) {
-    auto version = attr->Version;
+    auto version = attr->getVersion();
     AvailabilityDomain ignoredDomain;
     AvailabilityInference::updateBeforeAvailabilityDomainForFallback(
         attr, getASTContext(), ignoredDomain, version);

lib/Sema/TypeCheckAttr.cpp

@@ -5122,6 +5122,13 @@ void AttributeChecker::checkBackDeployedAttrs(
     ActiveAttr = AttrAndRange->first;
 
   for (auto *Attr : Attrs) {
+    auto Domain = Attr->getAvailabilityDomain();
+    if (!Domain.isVersionValid(Attr->getParsedVersion())) {
+      diagnose(Attr->getLocation(),
+               diag::availability_invalid_version_number_for_domain,
+               Attr->getParsedVersion(), Domain);
+    }
+
     // Back deployment only makes sense for public declarations.
     if (diagnoseAndRemoveAttrIfDeclIsNonPublic(Attr, /*isError=*/true))
       continue;
@@ -5169,7 +5176,7 @@ void AttributeChecker::checkBackDeployedAttrs(
     }
 
     auto AtLoc = Attr->AtLoc;
-    auto Platform = Attr->Platform;
+    auto Platform = Attr->getPlatform();
 
     if (!seenPlatforms.insert({Platform, AtLoc}).second) {
       // We've seen the platform before, emit error to the previous one which
@@ -5210,9 +5217,8 @@ void AttributeChecker::checkBackDeployedAttrs(
         D->getLoc(), D->getInnermostDeclContext());
 
     // Unavailable decls cannot be back deployed.
-    auto backDeployedDomain = Attr->getAvailabilityDomain();
-    if (availability.containsUnavailableDomain(backDeployedDomain)) {
-      auto domainForDiagnostics = backDeployedDomain;
+    if (availability.containsUnavailableDomain(Domain)) {
+      auto domainForDiagnostics = Domain;
       llvm::VersionTuple ignoredVersion;
 
       AvailabilityInference::updateBeforeAvailabilityDomainForFallback(
@@ -5244,7 +5250,7 @@ void AttributeChecker::checkBackDeployedAttrs(
     if (auto availableRangeAttrPair =
             getSemanticAvailableRangeDeclAndAttr(VD)) {
       auto beforeDomain = Attr->getAvailabilityDomain();
-      auto beforeVersion = Attr->Version;
+      auto beforeVersion = Attr->getVersion();
       auto availableAttr = availableRangeAttrPair.value().first;
       auto introVersion = availableAttr.getIntroduced().value();
       AvailabilityDomain introDomain = availableAttr.getDomain();
@@ -5254,7 +5260,7 @@ void AttributeChecker::checkBackDeployedAttrs(
       AvailabilityInference::updateIntroducedAvailabilityDomainForFallback(
           availableAttr, Ctx, introDomain, introVersion);
 
-      if (Attr->Version <= introVersion) {
+      if (beforeVersion <= introVersion) {
         diagnose(AtLoc, diag::attr_has_no_effect_decl_not_available_before,
                  Attr, VD, beforeDomain, AvailabilityRange(beforeVersion));
         diagnose(availableAttr.getParsedAttr()->AtLoc,

lib/Serialization/Serialization.cpp

@@ -3164,14 +3164,14 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
 
     case DeclAttrKind::BackDeployed: {
       auto *theAttr = cast<BackDeployedAttr>(DA);
-      ENCODE_VER_TUPLE(Version,
-                       std::optional<llvm::VersionTuple>(theAttr->Version));
+      ENCODE_VER_TUPLE(
+          Version, std::optional<llvm::VersionTuple>(theAttr->getVersion()));
       auto abbrCode = S.DeclTypeAbbrCodes[BackDeployedDeclAttrLayout::Code];
       BackDeployedDeclAttrLayout::emitRecord(
           S.Out, S.ScratchRecord, abbrCode,
           theAttr->isImplicit(),
           LIST_VER_TUPLE_PIECES(Version),
-          static_cast<unsigned>(theAttr->Platform));
+          static_cast<unsigned>(theAttr->getPlatform()));
       return;
     }
 

test/ModuleInterface/back-deployed-attr.swift

@@ -72,6 +72,21 @@ public func backDeployTopLevelFunc_macOS() -> Int {
 #endif
 }
 
+// CHECK: @backDeployed(before: macOS 26.0, iOS 26.0, tvOS 26.0, watchOS 26.0, visionOS 26.0)
+// CHECK: public func backDeployedBeforeVersionsMappingTo26() -> Swift.Int { return 26 }
+@backDeployed(before: macOS 16.0, iOS 19.0, tvOS 19.0, watchOS 12.0, visionOS 3.0)
+public func backDeployedBeforeVersionsMappingTo26() -> Int { return 26 }
+
+// CHECK: @backDeployed(before: macOS 27.0, iOS 27.0, tvOS 27.0, watchOS 27.0, visionOS 27.0)
+// CHECK: public func backDeployedBeforeVersionsMappingTo27() -> Swift.Int { return 27 }
+@backDeployed(before: macOS 17.0, iOS 20.0, tvOS 20.0, watchOS 13.0, visionOS 4.0)
+public func backDeployedBeforeVersionsMappingTo27() -> Int { return 27 }
+
+// CHECK: @backDeployed(before: macOS 26.0, iOS 26.0, tvOS 26.0, watchOS 26.0, visionOS 26.0)
+// CHECK: public func backDeployedBefore26() -> Swift.Int { return 26 }
+@backDeployed(before: macOS 26.0, iOS 26.0, tvOS 26.0, watchOS 26.0, visionOS 26.0)
+public func backDeployedBefore26() -> Int { return 26 }
+
 // MARK: - Availability macros
 
 // CHECK: @backDeployed(before: macOS 12.1)

test/SILGen/back_deployed_attr.swift

@@ -100,3 +100,15 @@ public func backDeployedNonisolatedNonsending() async -> Int {
   // CHECK:   apply [[SHIPPING_FN]](%0)
   return 0
 }
+
+// CHECK-LABEL: sil non_abi [serialized] [back_deployed_thunk] [ossa] @$s11back_deploy0A32DeployedBeforeVersionMappingTo26SiyFTwb :
+@backDeployed(before: macOS 16)
+public func backDeployedBeforeVersionMappingTo26() -> Int {
+  // CHECK: [[MAJOR:%.*]] = integer_literal $Builtin.Word, 26
+  // CHECK: [[MINOR:%.*]] = integer_literal $Builtin.Word, 0
+  // CHECK: [[PATCH:%.*]] = integer_literal $Builtin.Word, 0
+  // CHECK: [[OSVFN:%.*]] = function_ref @$ss26_stdlib_isOSVersionAtLeastyBi1_Bw_BwBwtF : $@convention(thin) (Builtin.Word, Builtin.Word, Builtin.Word) -> Builtin.Int1
+  // CHECK: [[AVAIL:%.*]] = apply [[OSVFN]]([[MAJOR]], [[MINOR]], [[PATCH]]) : $@convention(thin) (Builtin.Word, Builtin.Word, Builtin.Word) -> Builtin.Int1
+  // CHECK: cond_br [[AVAIL]]
+  return 0
+}

test/attr/attr_backDeployed.swift

@@ -205,6 +205,19 @@ extension TopLevelProtocol {
   public func backDeployedExtensionMethod() {}
 }
 
+@backDeployed(before: macOS 16.0, iOS 19.0, tvOS 19.0, watchOS 12.0, visionOS 3.0)
+public func backDeployedBeforeVersionsMappingTo26() -> Int { 26 }
+
+@backDeployed(before: macOS 17.0, iOS 20.0, tvOS 20.0, watchOS 13.0, visionOS 4.0)
+// expected-warning@-1 {{'17.0' is not a valid version number for macOS}}
+// expected-warning@-2 {{'20.0' is not a valid version number for iOS}}
+// expected-warning@-3 {{'20.0' is not a valid version number for tvOS}}
+// expected-warning@-4 {{'13.0' is not a valid version number for watchOS}}
+// expected-warning@-5 {{'4.0' is not a valid version number for visionOS}}
+public func backDeployedBeforeVersionsMappingTo27() -> Int { 27 }
+
+@backDeployed(before: macOS 26.0, iOS 26.0, tvOS 26.0, watchOS 26.0, visionOS 26.0)
+public func backDeployedBefore26() -> Int { 26 }
 
 // MARK: - Unsupported declaration kinds