Support __available__((swift_attr("@Sendable")))

include/swift/AST/Attr.def

@@ -605,7 +605,7 @@ CONTEXTUAL_SIMPLE_DECL_ATTR(async, Async,
   106)
 
 SIMPLE_DECL_ATTR(Sendable, Sendable,
-  OnFunc | OnConstructor | OnAccessor |
+  OnFunc | OnConstructor | OnAccessor | OnAnyClangDecl |
   ABIBreakingToAdd | ABIBreakingToRemove |
   APIBreakingToAdd | APIBreakingToRemove,
   107)

include/swift/AST/Attr.h

@@ -168,8 +168,9 @@ class DeclAttribute : public AttributeBase {
     );
 
     SWIFT_INLINE_BITFIELD(SynthesizedProtocolAttr, DeclAttribute,
-                          NumKnownProtocolKindBits,
-      kind : NumKnownProtocolKindBits
+                          NumKnownProtocolKindBits+1,
+      kind : NumKnownProtocolKindBits,
+      isUnchecked : 1
     );
   } Bits;
 
@@ -288,6 +289,9 @@ class DeclAttribute : public AttributeBase {
 
     /// Whether this attribute is only valid when distributed is enabled.
     DistributedOnly = 1ull << (unsigned(DeclKindIndex::Last_Decl) + 17),
+
+    /// Whether this attribute is valid on additional decls in ClangImporter.
+    OnAnyClangDecl = 1ull << (unsigned(DeclKindIndex::Last_Decl) + 18),
   };
 
   LLVM_READNONE
@@ -1276,11 +1280,13 @@ class SynthesizedProtocolAttr : public DeclAttribute {
 
 public:
   SynthesizedProtocolAttr(KnownProtocolKind protocolKind,
-                          LazyConformanceLoader *Loader)
+                          LazyConformanceLoader *Loader,
+                          bool isUnchecked)
     : DeclAttribute(DAK_SynthesizedProtocol, SourceLoc(), SourceRange(),
                     /*Implicit=*/true), Loader(Loader)
   {
     Bits.SynthesizedProtocolAttr.kind = unsigned(protocolKind);
+    Bits.SynthesizedProtocolAttr.isUnchecked = unsigned(isUnchecked);
   }
 
   /// Retrieve the known protocol kind naming the protocol to be
@@ -1289,6 +1295,10 @@ class SynthesizedProtocolAttr : public DeclAttribute {
     return KnownProtocolKind(Bits.SynthesizedProtocolAttr.kind);
   }
 
+  bool isUnchecked() const {
+    return bool(Bits.SynthesizedProtocolAttr.isUnchecked);
+  }
+
   /// Retrieve the lazy loader that will be used to populate the
   /// synthesized conformance.
   LazyConformanceLoader *getLazyLoader() const { return Loader; }
@@ -2217,6 +2227,15 @@ class DeclAttributes {
     return nullptr;
   }
 
+  /// Returns the "winning" \c NonSendableAttr or \c SendableAttr in this
+  /// attribute list, or \c nullptr if there are none.
+  const DeclAttribute *getEffectiveSendableAttr() const;
+
+  DeclAttribute *getEffectiveSendableAttr() {
+    return const_cast<DeclAttribute *>(
+         const_cast<const DeclAttributes *>(this)->getEffectiveSendableAttr());
+  }
+
 private:
   /// Predicate used to filter MatchingAttributeRange.
   template <typename ATTR, bool AllowInvalid> struct ToAttributeKind {

include/swift/AST/DiagnosticsClangImporter.def

@@ -85,6 +85,10 @@ NOTE(unresolvable_clang_decl_is_a_framework_bug,none,
 WARNING(clang_swift_attr_unhandled,none,
         "Ignoring unknown Swift attribute or modifier '%0'", (StringRef))
 
+WARNING(clang_error_code_must_be_sendable,none,
+        "cannot make error code type '%0' non-sendable because Swift errors "
+        "are always sendable", (StringRef))
+
 WARNING(implicit_bridging_header_imported_from_module,none,
         "implicit import of bridging header '%0' via module %1 "
         "is deprecated and will be removed in a later version of Swift",

include/swift/AST/FileUnit.h

@@ -17,7 +17,11 @@
 #include "swift/AST/RawComment.h"
 #include "swift/Basic/BasicSourceInfo.h"
 
+#include "llvm/ADT/PointerIntPair.h"
+
 namespace swift {
+class SynthesizedFileUnit;
+
 /// A container for module-scope declarations that itself provides a scope; the
 /// smallest unit of code organization.
 ///
@@ -33,19 +37,25 @@ class FileUnit : public DeclContext, public ASTAllocated<FileUnit> {
   friend class DirectOperatorLookupRequest;
   friend class DirectPrecedenceGroupLookupRequest;
 
-  // FIXME: Stick this in a PointerIntPair.
-  const FileUnitKind Kind;
+  // The pointer is FileUnit insted of SynthesizedFileUnit to break circularity.
+  llvm::PointerIntPair<FileUnit *, 3, FileUnitKind> SynthesizedFileAndKind;
 
 protected:
   FileUnit(FileUnitKind kind, ModuleDecl &M)
-    : DeclContext(DeclContextKind::FileUnit, &M), Kind(kind) {
+    : DeclContext(DeclContextKind::FileUnit, &M),
+      SynthesizedFileAndKind(nullptr, kind) {
   }
 
 public:
   FileUnitKind getKind() const {
-    return Kind;
+    return SynthesizedFileAndKind.getInt();
   }
 
+  /// Returns the synthesized file for this source file, if it exists.
+  SynthesizedFileUnit *getSynthesizedFile() const;
+
+  SynthesizedFileUnit &getOrCreateSynthesizedFile();
+
   /// Look up a (possibly overloaded) value set at top-level scope
   /// (but with the specified access path, which may come from an import decl)
   /// within this file.

include/swift/AST/PrintOptions.h

@@ -235,6 +235,10 @@ struct PrintOptions {
   /// Whether to print unavailable parts of the AST.
   bool SkipUnavailable = false;
 
+  /// Whether to print synthesized extensions created by '@_nonSendable', even
+  /// if SkipImplicit or SkipUnavailable is set.
+  bool AlwaysPrintNonSendableExtensions = true;
+
   bool SkipSwiftPrivateClangDecls = false;
 
   /// Whether to skip internal stdlib declarations.
@@ -667,6 +671,7 @@ struct PrintOptions {
     PO.ShouldQualifyNestedDeclarations = QualifyNestedDeclarations::TypesOnly;
     PO.PrintParameterSpecifiers = true;
     PO.SkipImplicit = true;
+    PO.AlwaysPrintNonSendableExtensions = false;
     PO.AlwaysTryPrintParameterLabels = true;
     return PO;
   }

include/swift/AST/ProtocolConformance.h

@@ -514,6 +514,13 @@ class NormalProtocolConformance : public RootProtocolConformance,
     return ContextAndBits.getInt() & UncheckedFlag;
   }
 
+  /// Mark the conformance as unchecked (equivalent to the @unchecked
+  /// conformance attribute).
+  void setUnchecked() {
+    // OK to mutate because the flags are not part of the folding set node ID.
+    ContextAndBits.setInt(ContextAndBits.getInt() | UncheckedFlag);
+  }
+
   /// Get the kind of source from which this conformance comes.
   ConformanceEntryKind getSourceKind() const {
     return SourceKindAndImplyingConformance.getInt();

include/swift/AST/SourceFile.h

@@ -89,9 +89,6 @@ class SourceFile final : public FileUnit {
   /// same module.
   mutable Identifier PrivateDiscriminator;
 
-  /// A synthesized file corresponding to this file, created on-demand.
-  SynthesizedFileUnit *SynthesizedFile = nullptr;
-
   /// The root TypeRefinementContext for this SourceFile.
   ///
   /// This is set during type checking.
@@ -409,11 +406,6 @@ class SourceFile final : public FileUnit {
   Optional<ExternalSourceLocs::RawLocs>
   getExternalRawLocsForDecl(const Decl *D) const override;
 
-  /// Returns the synthesized file for this source file, if it exists.
-  SynthesizedFileUnit *getSynthesizedFile() const { return SynthesizedFile; };
-
-  SynthesizedFileUnit &getOrCreateSynthesizedFile();
-
   virtual bool walk(ASTWalker &walker) override;
 
   /// The buffer ID for the file that was imported, or None if there

include/swift/AST/SynthesizedFileUnit.h

@@ -18,14 +18,12 @@
 
 namespace swift {
 
-class SourceFile;
-
 /// A container for synthesized declarations, attached to a `SourceFile`.
 ///
 /// Currently, only module-level synthesized declarations are supported.
 class SynthesizedFileUnit final : public FileUnit {
   /// The parent source file.
-  SourceFile &SF;
+  FileUnit &FU;
 
   /// Synthesized top level declarations.
   TinyPtrVector<Decl *> TopLevelDecls;
@@ -36,11 +34,11 @@ class SynthesizedFileUnit final : public FileUnit {
   mutable Identifier PrivateDiscriminator;
 
 public:
-  SynthesizedFileUnit(SourceFile &SF);
+  SynthesizedFileUnit(FileUnit &FU);
   ~SynthesizedFileUnit() = default;
 
   /// Returns the parent source file.
-  SourceFile &getSourceFile() const { return SF; }
+  FileUnit &getFileUnit() const { return FU; }
 
   /// Add a synthesized top-level declaration.
   void addTopLevelDecl(Decl *D) { TopLevelDecls.push_back(D); }

lib/AST/ASTPrinter.cpp

@@ -1769,6 +1769,24 @@ bool ShouldPrintChecker::shouldPrint(const Pattern *P,
   return ShouldPrint;
 }
 
+bool isNonSendableExtension(const Decl *D) {
+  ASTContext &ctx = D->getASTContext();
+
+  const ExtensionDecl *ED = dyn_cast<ExtensionDecl>(D);
+  if (!ED || !ED->getAttrs().isUnavailable(ctx))
+    return false;
+
+  auto nonSendable =
+      ED->getExtendedNominal()->getAttrs().getEffectiveSendableAttr();
+  if (!isa_and_nonnull<NonSendableAttr>(nonSendable))
+    return false;
+
+  // GetImplicitSendableRequest::evaluate() creates its extension with the
+  // attribute's AtLoc, so this is a good way to quickly check if the extension
+  // was synthesized for an '@_nonSendable' attribute.
+  return ED->getLocFromSource() == nonSendable->AtLoc;
+}
+
 bool ShouldPrintChecker::shouldPrint(const Decl *D,
                                      const PrintOptions &Options) {
   #if SWIFT_BUILD_ONLY_SYNTAXPARSERLIB
@@ -1791,15 +1809,18 @@ bool ShouldPrintChecker::shouldPrint(const Decl *D,
     return false;
   }
 
-  if (Options.SkipImplicit && D->isImplicit()) {
-    const auto &IgnoreList = Options.TreatAsExplicitDeclList;
-    if (std::find(IgnoreList.begin(), IgnoreList.end(), D) == IgnoreList.end())
+  // Optionally skip these checks for extensions synthesized for '@_nonSendable'
+  if (!Options.AlwaysPrintNonSendableExtensions || !isNonSendableExtension(D)) {
+    if (Options.SkipImplicit && D->isImplicit()) {
+      const auto &IgnoreList = Options.TreatAsExplicitDeclList;
+      if (!llvm::is_contained(IgnoreList, D))
         return false;
-  }
+    }
 
-  if (Options.SkipUnavailable &&
-      D->getAttrs().isUnavailable(D->getASTContext()))
-    return false;
+    if (Options.SkipUnavailable &&
+        D->getAttrs().isUnavailable(D->getASTContext()))
+      return false;
+  }
 
   if (Options.ExplodeEnumCaseDecls) {
     if (isa<EnumElementDecl>(D))
@@ -5901,6 +5922,7 @@ swift::getInheritedForPrinting(
   // Collect synthesized conformances.
   auto &ctx = decl->getASTContext();
   llvm::SetVector<ProtocolDecl *> protocols;
+  llvm::TinyPtrVector<ProtocolDecl *> uncheckedProtocols;
   for (auto attr : decl->getAttrs().getAttributes<SynthesizedProtocolAttr>()) {
     if (auto *proto = ctx.getProtocol(attr->getProtocolKind())) {
       // The SerialExecutor conformance is only synthesized on the root
@@ -5913,11 +5935,14 @@ swift::getInheritedForPrinting(
           cast<EnumDecl>(decl)->hasRawType())
         continue;
       protocols.insert(proto);
+      if (attr->isUnchecked())
+        uncheckedProtocols.push_back(proto);
     }
   }
 
   for (size_t i = 0; i < protocols.size(); i++) {
     auto proto = protocols[i];
+    bool isUnchecked = llvm::is_contained(uncheckedProtocols, proto);
 
     if (!options.shouldPrint(proto)) {
       // If private stdlib protocols are skipped and this is a private stdlib
@@ -5928,12 +5953,14 @@ swift::getInheritedForPrinting(
           proto->isPrivateStdlibDecl(!options.SkipUnderscoredStdlibProtocols)) {
         auto inheritedProtocols = proto->getInheritedProtocols();
         protocols.insert(inheritedProtocols.begin(), inheritedProtocols.end());
+        if (isUnchecked)
+          copy(inheritedProtocols, std::back_inserter(uncheckedProtocols));
       }
       continue;
     }
 
     Results.push_back({TypeLoc::withoutLoc(proto->getDeclaredInterfaceType()),
-                       /*isUnchecked=*/false});
+                       isUnchecked});
   }
 }
 

lib/AST/Attr.cpp

@@ -131,6 +131,8 @@ DeclAttrKind DeclAttribute::getAttrKindFromString(StringRef Str) {
 
 /// Returns true if this attribute can appear on the specified decl.
 bool DeclAttribute::canAttributeAppearOnDecl(DeclAttrKind DK, const Decl *D) {
+  if ((getOptions(DK) & OnAnyClangDecl) && D->hasClangNode())
+    return true;
   return canAttributeAppearOnDeclKind(DK, D->getKind());
 }
 
@@ -699,6 +701,13 @@ void DeclAttributes::print(ASTPrinter &Printer, const PrintOptions &Options,
     if (Options.excludeAttrKind(DA->getKind()))
       continue;
 
+    // If this attribute is only allowed because this is a Clang decl, don't
+    // print it.
+    if (D && D->hasClangNode()
+        && !DeclAttribute::canAttributeAppearOnDeclKind(
+                               DA->getKind(), D->getKind()))
+      continue;
+
     // Be careful not to coalesce `@available(swift 5)` with other short
     // `available' attributes.
     if (auto *availableAttr = dyn_cast<AvailableAttr>(DA)) {
@@ -2102,6 +2111,23 @@ TypeSequenceAttr *TypeSequenceAttr::create(ASTContext &Ctx, SourceLoc atLoc,
   return new (mem) TypeSequenceAttr(atLoc, range);
 }
 
+const DeclAttribute *
+DeclAttributes::getEffectiveSendableAttr() const {
+  const NonSendableAttr *assumedAttr = nullptr;
+
+  for (auto attr : getAttributes<NonSendableAttr>()) {
+    if (attr->Specificity == NonSendableKind::Specific)
+      return attr;
+    if (!assumedAttr)
+      assumedAttr = attr;
+  }
+
+  if (auto sendableAttr = getAttribute<SendableAttr>())
+    return sendableAttr;
+
+  return assumedAttr;
+}
+
 void swift::simple_display(llvm::raw_ostream &out, const DeclAttribute *attr) {
   if (attr)
     attr->print(out);

lib/AST/ConformanceLookupTable.cpp

@@ -904,6 +904,8 @@ ConformanceLookupTable::getConformance(NominalTypeDecl *nominal,
           // Set the conformance loader to the loader stashed inside
           // the attribute.
           normalConf->setLazyLoader(attr->getLazyLoader(), /*context=*/0);
+          if (attr->isUnchecked())
+            normalConf->setUnchecked();
           break;
         }
       }