Merge pull request swiftlang#39530 from beccadax/return-to-sender

Author: swift-ci

docs/ReferenceGuides/UnderscoredAttributes.md

@@ -376,6 +376,22 @@ override.
 This attribute and the corresponding `-warn-implicit-overrides` flag are
 used when compiling the standard library and overlays.
 
+## `@_nonSendable`
+
+There is no clang attribute to add a Swift conformance to an imported type, but
+there *is* a clang attribute to add a Swift attribute to an imported type. So
+`@Sendable` (which is not normally allowed on types) is used from clang headers
+to indicate that an unconstrained, fully available `Sendable` conformance should
+be added to a given type, while `@_nonSendable` indicates that an unavailable
+`Sendable` conformance should be added to it.
+
+`@_nonSendable` can have no options after it, in which case it "beats"
+`@Sendable` if both are applied to the same declaration, or it can have
+`(_assumed)` after it, in which case `@Sendable` "beats" it.
+`@_nonSendable(_assumed)` is intended to be used when mass-marking whole regions
+of a header as non-`Sendable` so that you can make spot exceptions with
+`@Sendable`.   
+
 ## `@_objc_non_lazy_realization`
 
 Marks a class as being non-lazily (i.e. eagerly) [realized](/docs/Lexicon.md#realization).

include/swift/AST/Attr.def

@@ -665,6 +665,13 @@ SIMPLE_DECL_ATTR(_assemblyVision, EmitAssemblyVisionRemarks,
   ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIStableToRemove,
   120)
 
+DECL_ATTR(_nonSendable, NonSendable,
+  OnNominalType |
+  UserInaccessible | AllowMultipleAttributes |
+  ABIStableToAdd | ABIBreakingToRemove |
+  APIStableToAdd | APIBreakingToRemove,
+  121)
+
 // If you're adding a new underscored attribute here, please document it in
 // docs/ReferenceGuides/UnderscoredAttributes.md.
 

include/swift/AST/Attr.h

@@ -2030,6 +2030,37 @@ class TransposeAttr final
   }
 };
 
+enum class NonSendableKind : uint8_t {
+  /// A plain '@_nonSendable' attribute. Should be applied directly to
+  /// particular declarations; overrides even an explicit 'Sendable'
+  /// conformance.
+  Specific,
+
+  /// A '@_nonSendable(_assumed)' attribute. Should be applied to large swaths
+  /// of declarations; does not override explicit 'Sendable' conformances.
+  Assumed
+};
+
+/// Marks a declaration as explicitly non-Sendable.
+class NonSendableAttr : public DeclAttribute {
+public:
+  NonSendableAttr(SourceLoc AtLoc, SourceRange Range,
+                  NonSendableKind Specificity, bool Implicit = false)
+    : DeclAttribute(DAK_NonSendable, AtLoc, Range, Implicit),
+      Specificity(Specificity)
+  {}
+
+  NonSendableAttr(NonSendableKind Specificity, bool Implicit = false)
+    : NonSendableAttr(SourceLoc(), SourceRange(), Specificity, Implicit) {}
+
+  /// Was this '@_nonSendable(_assumed)'?
+  const NonSendableKind Specificity;
+
+  static bool classof(const DeclAttribute *DA) {
+    return DA->getKind() == DAK_NonSendable;
+  }
+};
+
 /// Attributes that may be applied to declarations.
 class DeclAttributes {
   /// Linked list of declaration attributes.

include/swift/AST/Decl.h

@@ -1284,6 +1284,8 @@ class ExtensionDecl final : public GenericContext, public Decl,
   SourceLoc getStartLoc() const { return ExtensionLoc; }
   SourceLoc getLocFromSource() const { return ExtensionLoc; }
   SourceRange getSourceRange() const {
+    if (!Braces.isValid())
+      return SourceRange(ExtensionLoc);
     return { ExtensionLoc, Braces.End };
   }
 

include/swift/AST/DiagnosticsParse.def

@@ -1604,10 +1604,6 @@ ERROR(opened_attribute_id_value,none,
 ERROR(opened_attribute_expected_rparen,none,
       "expected ')' after id value for 'opened' attribute", ())
 
-// effects
-ERROR(effects_attribute_expect_option,none,
-      "expected '%0' option (readnone, readonly, readwrite)", (StringRef))
-
 // unowned
 ERROR(attr_unowned_invalid_specifier,none,
       "expected 'safe' or 'unsafe'", ())

include/swift/AST/SynthesizedFileUnit.h

@@ -28,7 +28,7 @@ class SynthesizedFileUnit final : public FileUnit {
   SourceFile &SF;
 
   /// Synthesized top level declarations.
-  TinyPtrVector<ValueDecl *> TopLevelDecls;
+  TinyPtrVector<Decl *> TopLevelDecls;
 
   /// A unique identifier representing this file; used to mark private decls
   /// within the file to keep them from conflicting with other files in the
@@ -43,7 +43,7 @@ class SynthesizedFileUnit final : public FileUnit {
   SourceFile &getSourceFile() const { return SF; }
 
   /// Add a synthesized top-level declaration.
-  void addTopLevelDecl(ValueDecl *D) { TopLevelDecls.push_back(D); }
+  void addTopLevelDecl(Decl *D) { TopLevelDecls.push_back(D); }
 
   virtual void lookupValue(DeclName name, NLKind lookupKind,
                            SmallVectorImpl<ValueDecl *> &result) const override;
@@ -56,7 +56,7 @@ class SynthesizedFileUnit final : public FileUnit {
 
   void getTopLevelDecls(SmallVectorImpl<Decl*> &results) const override;
 
-  ArrayRef<ValueDecl *> getTopLevelDecls() const {
+  ArrayRef<Decl *> getTopLevelDecls() const {
     return TopLevelDecls;
   };
 

lib/AST/ASTPrinter.cpp

@@ -263,7 +263,8 @@ PrintOptions PrintOptions::printSwiftInterfaceFile(ModuleDecl *ModuleToPrint,
     DAK_SetterAccess,
     DAK_Lazy,
     DAK_StaticInitializeObjCMetadata,
-    DAK_RestatedObjCConformance
+    DAK_RestatedObjCConformance,
+    DAK_NonSendable,
   };
 
   return result;

lib/AST/Attr.cpp

@@ -874,6 +874,7 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
   case DAK_ReferenceOwnership:
   case DAK_Effects:
   case DAK_Optimize:
+  case DAK_NonSendable:
     if (DeclAttribute::isDeclModifier(getKind())) {
       Printer.printKeyword(getAttrName(), Options);
     } else if (Options.IsForSwiftInterface && getKind() == DAK_ResultBuilder) {
@@ -1226,6 +1227,15 @@ StringRef DeclAttribute::getAttrName() const {
     }
     llvm_unreachable("Invalid inline kind");
   }
+  case DAK_NonSendable: {
+    switch (cast<NonSendableAttr>(this)->Specificity) {
+    case NonSendableKind::Specific:
+      return "_nonSendable";
+    case NonSendableKind::Assumed:
+      return "_nonSendable(_assumed)";
+    }
+    llvm_unreachable("Invalid nonSendable kind");
+  }
   case DAK_Optimize: {
     switch (cast<OptimizeAttr>(this)->getMode()) {
     case OptimizationMode::NoOptimization:

lib/AST/Module.cpp

@@ -2996,8 +2996,11 @@ void SynthesizedFileUnit::lookupValue(
     DeclName name, NLKind lookupKind,
     SmallVectorImpl<ValueDecl *> &result) const {
   for (auto *decl : TopLevelDecls) {
-    if (decl->getName().matchesRef(name))
-      result.push_back(decl);
+    if (auto VD = dyn_cast<ValueDecl>(decl)) {
+      if (VD->getName().matchesRef(name)) {
+        result.push_back(VD);
+      }
+    }
   }
 }