[SE-0302] Implement '@unchecked Sendable' syntax.

include/swift/AST/ASTContext.h

@@ -1019,7 +1019,8 @@ class ASTContext final {
                  ProtocolDecl *protocol,
                  SourceLoc loc,
                  DeclContext *dc,
-                 ProtocolConformanceState state);
+                 ProtocolConformanceState state,
+                 bool isUnchecked);
 
   /// Produce a self-conformance for the given protocol.
   SelfProtocolConformance *

include/swift/AST/ASTPrinter.h

@@ -17,6 +17,7 @@
 #include "swift/Basic/QuotedString.h"
 #include "swift/Basic/UUID.h"
 #include "swift/AST/Identifier.h"
+#include "swift/AST/Decl.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/DenseSet.h"
@@ -351,8 +352,9 @@ void printEnumElementsAsCases(
     llvm::DenseSet<EnumElementDecl *> &UnhandledElements,
     llvm::raw_ostream &OS);
 
-void getInheritedForPrinting(const Decl *decl, const PrintOptions &options,
-                             llvm::SmallVectorImpl<TypeLoc> &Results);
+void getInheritedForPrinting(
+  const Decl *decl, const PrintOptions &options,
+  llvm::SmallVectorImpl<InheritedEntry> &Results);
 
 StringRef getAccessorKindString(AccessorKind value);
 

include/swift/AST/Attr.def

@@ -55,6 +55,7 @@ TYPE_ATTR(differentiable)
 TYPE_ATTR(noDerivative)
 TYPE_ATTR(async)
 TYPE_ATTR(Sendable)
+TYPE_ATTR(unchecked)
 
 // SIL-specific attributes
 TYPE_ATTR(block_storage)

include/swift/AST/Decl.h

@@ -1209,6 +1209,17 @@ class ImportDecl final : public Decl,
   }
 };
 
+/// An entry in the "inherited" list of a type or extension.
+struct InheritedEntry : public TypeLoc {
+  /// Whether there was an @unchecked attribute.
+  bool isUnchecked = false;
+
+  InheritedEntry(const TypeLoc &typeLoc);
+
+  InheritedEntry(const TypeLoc &typeLoc, bool isUnchecked)
+    : TypeLoc(typeLoc), isUnchecked(isUnchecked) { }
+};
+
 /// ExtensionDecl - This represents a type extension containing methods
 /// associated with the type.  This is not a ValueDecl and has no Type because
 /// there are no runtime values of the Extension's type.  
@@ -1227,7 +1238,7 @@ class ExtensionDecl final : public GenericContext, public Decl,
   /// extended nominal.
   llvm::PointerIntPair<NominalTypeDecl *, 1, bool> ExtendedNominal;
 
-  ArrayRef<TypeLoc> Inherited;
+  ArrayRef<InheritedEntry> Inherited;
 
   /// The next extension in the linked list of extensions.
   ///
@@ -1246,7 +1257,7 @@ class ExtensionDecl final : public GenericContext, public Decl,
   friend class IterableDeclContext;
 
   ExtensionDecl(SourceLoc extensionLoc, TypeRepr *extendedType,
-                ArrayRef<TypeLoc> inherited,
+                ArrayRef<InheritedEntry> inherited,
                 DeclContext *parent,
                 TrailingWhereClause *trailingWhereClause);
 
@@ -1271,7 +1282,7 @@ class ExtensionDecl final : public GenericContext, public Decl,
   /// Create a new extension declaration.
   static ExtensionDecl *create(ASTContext &ctx, SourceLoc extensionLoc,
                                TypeRepr *extendedType,
-                               ArrayRef<TypeLoc> inherited,
+                               ArrayRef<InheritedEntry> inherited,
                                DeclContext *parent,
                                TrailingWhereClause *trailingWhereClause,
                                ClangNode clangNode = ClangNode());
@@ -1326,9 +1337,9 @@ class ExtensionDecl final : public GenericContext, public Decl,
 
   /// Retrieve the set of protocols that this type inherits (i.e,
   /// explicitly conforms to).
-  ArrayRef<TypeLoc> getInherited() const { return Inherited; }
+  ArrayRef<InheritedEntry> getInherited() const { return Inherited; }
 
-  void setInherited(ArrayRef<TypeLoc> i) { Inherited = i; }
+  void setInherited(ArrayRef<InheritedEntry> i) { Inherited = i; }
 
   bool hasDefaultAccessLevel() const {
     return Bits.ExtensionDecl.DefaultAndMaxAccessLevel != 0;
@@ -2538,12 +2549,12 @@ class ValueDecl : public Decl {
 
 /// This is a common base class for declarations which declare a type.
 class TypeDecl : public ValueDecl {
-  ArrayRef<TypeLoc> Inherited;
+  ArrayRef<InheritedEntry> Inherited;
 
 protected:
   TypeDecl(DeclKind K, llvm::PointerUnion<DeclContext *, ASTContext *> context,
            Identifier name, SourceLoc NameLoc,
-           ArrayRef<TypeLoc> inherited) :
+           ArrayRef<InheritedEntry> inherited) :
     ValueDecl(K, context, name, NameLoc), Inherited(inherited) {}
 
 public:
@@ -2561,9 +2572,9 @@ class TypeDecl : public ValueDecl {
 
   /// Retrieve the set of protocols that this type inherits (i.e,
   /// explicitly conforms to).
-  ArrayRef<TypeLoc> getInherited() const { return Inherited; }
+  ArrayRef<InheritedEntry> getInherited() const { return Inherited; }
 
-  void setInherited(ArrayRef<TypeLoc> i) { Inherited = i; }
+  void setInherited(ArrayRef<InheritedEntry> i) { Inherited = i; }
 
   static bool classof(const Decl *D) {
     return D->getKind() >= DeclKind::First_TypeDecl &&
@@ -2588,7 +2599,7 @@ class GenericTypeDecl : public GenericContext, public TypeDecl {
 public:
   GenericTypeDecl(DeclKind K, DeclContext *DC,
                   Identifier name, SourceLoc nameLoc,
-                  ArrayRef<TypeLoc> inherited,
+                  ArrayRef<InheritedEntry> inherited,
                   GenericParamList *GenericParams);
 
   // Resolve ambiguity due to multiple base classes.
@@ -3115,7 +3126,7 @@ class NominalTypeDecl : public GenericTypeDecl, public IterableDeclContext {
 
   NominalTypeDecl(DeclKind K, DeclContext *DC, Identifier name,
                   SourceLoc NameLoc,
-                  ArrayRef<TypeLoc> inherited,
+                  ArrayRef<InheritedEntry> inherited,
                   GenericParamList *GenericParams) :
     GenericTypeDecl(K, DC, name, NameLoc, inherited, GenericParams),
     IterableDeclContext(IterableDeclContextKind::NominalTypeDecl)
@@ -3411,7 +3422,7 @@ class EnumDecl final : public NominalTypeDecl {
 
 public:
   EnumDecl(SourceLoc EnumLoc, Identifier Name, SourceLoc NameLoc,
-            ArrayRef<TypeLoc> Inherited,
+            ArrayRef<InheritedEntry> Inherited,
             GenericParamList *GenericParams, DeclContext *DC);
 
   SourceLoc getStartLoc() const { return EnumLoc; }
@@ -3579,7 +3590,7 @@ class StructDecl final : public NominalTypeDecl {
 
 public:
   StructDecl(SourceLoc StructLoc, Identifier Name, SourceLoc NameLoc,
-             ArrayRef<TypeLoc> Inherited,
+             ArrayRef<InheritedEntry> Inherited,
              GenericParamList *GenericParams, DeclContext *DC);
 
   SourceLoc getStartLoc() const { return StructLoc; }
@@ -3725,7 +3736,7 @@ class ClassDecl final : public NominalTypeDecl {
 
 public:
   ClassDecl(SourceLoc ClassLoc, Identifier Name, SourceLoc NameLoc,
-            ArrayRef<TypeLoc> Inherited,
+            ArrayRef<InheritedEntry> Inherited,
             GenericParamList *GenericParams, DeclContext *DC,
             bool isActor);
 
@@ -4160,7 +4171,7 @@ class ProtocolDecl final : public NominalTypeDecl {
 
 public:
   ProtocolDecl(DeclContext *DC, SourceLoc ProtocolLoc, SourceLoc NameLoc,
-               Identifier Name, ArrayRef<TypeLoc> Inherited,
+               Identifier Name, ArrayRef<InheritedEntry> Inherited,
                TrailingWhereClause *TrailingWhere);
 
   using Decl::getASTContext;

include/swift/AST/DiagnosticsSema.def

@@ -4516,16 +4516,23 @@ ERROR(concurrent_value_class_mutable_property,none,
       (DeclName, DescriptiveDeclKind, DeclName))
 ERROR(concurrent_value_outside_source_file,none,
       "conformance to 'Sendable' must occur in the same source file as "
-      "%0 %1; use 'UnsafeSendable' for retroactive conformance",
+      "%0 %1; use '@unchecked Sendable' for retroactive conformance",
       (DescriptiveDeclKind, DeclName))
 ERROR(concurrent_value_nonfinal_class,none,
       "non-final class %0 cannot conform to `Sendable`; "
-      "use `UnsafeSendable`", (DeclName))
+      "use `@unchecked Sendable`", (DeclName))
 ERROR(concurrent_value_inherit,none,
       "`Sendable` class %1 cannot inherit from another class"
       "%select{| other than 'NSObject'}0",
       (bool, DeclName))
 
+WARNING(unchecked_conformance_not_special,none,
+      "@unchecked conformance to %0 has no meaning", (Type))
+ERROR(unchecked_not_inheritance_clause,none,
+      "'unchecked' attribute only applies in inheritance clauses", ())
+ERROR(unchecked_not_existential,none,
+      "'unchecked' attribute cannot apply to non-protocol type %0", (Type))
+
 ERROR(nonisolated_let,none,
       "'nonisolated' is meaningless on 'let' declarations because "
       "they are immutable",

include/swift/AST/NameLookup.h

@@ -503,6 +503,19 @@ void filterForDiscriminator(SmallVectorImpl<Result> &results,
 
 } // end namespace namelookup
 
+/// Describes an inherited nominal entry.
+struct InheritedNominalEntry : Located<NominalTypeDecl *> {
+  /// The location of the "unchecked" attribute, if present.
+  SourceLoc uncheckedLoc;
+
+  InheritedNominalEntry() { }
+
+  InheritedNominalEntry(
+    NominalTypeDecl *item, SourceLoc loc,
+    SourceLoc uncheckedLoc
+  ) : Located(item, loc), uncheckedLoc(uncheckedLoc) { }
+};
+
 /// Retrieve the set of nominal type declarations that are directly
 /// "inherited" by the given declaration at a particular position in the
 /// list of "inherited" types.
@@ -511,15 +524,15 @@ void filterForDiscriminator(SmallVectorImpl<Result> &results,
 /// AnyObject type, set \c anyObject true.
 void getDirectlyInheritedNominalTypeDecls(
     llvm::PointerUnion<const TypeDecl *, const ExtensionDecl *> decl,
-    unsigned i, llvm::SmallVectorImpl<Located<NominalTypeDecl *>> &result,
+    unsigned i, llvm::SmallVectorImpl<InheritedNominalEntry> &result,
     bool &anyObject);
 
 /// Retrieve the set of nominal type declarations that are directly
 /// "inherited" by the given declaration, looking through typealiases
 /// and splitting out the components of compositions.
 ///
 /// If we come across the AnyObject type, set \c anyObject true.
-SmallVector<Located<NominalTypeDecl *>, 4> getDirectlyInheritedNominalTypeDecls(
+SmallVector<InheritedNominalEntry, 4> getDirectlyInheritedNominalTypeDecls(
     llvm::PointerUnion<const TypeDecl *, const ExtensionDecl *> decl,
     bool &anyObject);
 

include/swift/AST/ProtocolConformance.h

@@ -412,11 +412,20 @@ class NormalProtocolConformance : public RootProtocolConformance,
   /// The location of this protocol conformance in the source.
   SourceLoc Loc;
 
+  // Flag bits used in ContextAndBits.
+  enum {
+    /// The conformance is invalid.
+    InvalidFlag = 0x01,
+
+    /// The conformance was labeled with @unchecked.
+    UncheckedFlag = 0x02,
+  };
+
   /// The declaration context containing the ExtensionDecl or
   /// NominalTypeDecl that declared the conformance.
   ///
-  /// Also stores the "invalid" bit.
-  llvm::PointerIntPair<DeclContext *, 1, bool> ContextAndInvalid;
+  /// Also stores the "invalid" and "unchecked" bits.
+  llvm::PointerIntPair<DeclContext *, 2, unsigned> ContextAndBits;
 
   /// The reason that this conformance exists.
   ///
@@ -457,11 +466,12 @@ class NormalProtocolConformance : public RootProtocolConformance,
 public:
   NormalProtocolConformance(Type conformingType, ProtocolDecl *protocol,
                             SourceLoc loc, DeclContext *dc,
-                            ProtocolConformanceState state)
+                            ProtocolConformanceState state,
+                            bool isUnchecked)
       : RootProtocolConformance(ProtocolConformanceKind::Normal,
                                 conformingType),
         ProtocolAndState(protocol, state), Loc(loc),
-        ContextAndInvalid(dc, false) {
+        ContextAndBits(dc, isUnchecked ? UncheckedFlag : 0) {
     assert(!conformingType->hasArchetype() &&
            "ProtocolConformances should store interface types");
   }
@@ -475,7 +485,7 @@ class NormalProtocolConformance : public RootProtocolConformance,
   /// Get the declaration context that contains the conforming extension or
   /// nominal type declaration.
   DeclContext *getDeclContext() const {
-    return ContextAndInvalid.getPointer();
+    return ContextAndBits.getPointer();
   }
 
   /// Get any additional requirements that are required for this conformance to
@@ -497,15 +507,20 @@ class NormalProtocolConformance : public RootProtocolConformance,
 
   /// Determine whether this conformance is invalid.
   bool isInvalid() const {
-    return ContextAndInvalid.getInt();
+    return ContextAndBits.getInt() & InvalidFlag;
   }
 
   /// Mark this conformance as invalid.
   void setInvalid() {
-    ContextAndInvalid.setInt(true);
+    ContextAndBits.setInt(ContextAndBits.getInt() | InvalidFlag);
     SignatureConformances = {};
   }
 
+  /// Whether this is an "unchecked" conformance.
+  bool isUnchecked() const {
+    return ContextAndBits.getInt() & UncheckedFlag;
+  }
+
   /// Get the kind of source from which this conformance comes.
   ConformanceEntryKind getSourceKind() const {
     return SourceKindAndImplyingConformance.getInt();

include/swift/AST/TypeLoc.h

@@ -29,7 +29,7 @@ class TypeRepr;
 
 /// TypeLoc - Provides source location information for a parsed type.
 /// A TypeLoc is stored in AST nodes which use an explicitly written type.
-class alignas(1 << TypeReprAlignInBits) TypeLoc final {
+class alignas(1 << TypeReprAlignInBits) TypeLoc {
   Type Ty;
   TypeRepr *TyR = nullptr;
 

include/swift/AST/TypeRepr.h

@@ -135,6 +135,10 @@ class alignas(1 << TypeReprAlignInBits) TypeRepr {
   SourceLoc getEndLoc() const;
   SourceRange getSourceRange() const;
 
+  /// Find an @unchecked attribute and return its source location, or return
+  /// an invalid source location if there is no such attribute.
+  SourceLoc findUncheckedAttrLoc() const;
+
   /// Is this type grammatically a type-simple?
   inline bool isSimple() const; // bottom of this file
 

include/swift/Parse/Parser.h

@@ -1127,7 +1127,7 @@ class Parser {
 
   ParserResult<ImportDecl> parseDeclImport(ParseDeclOptions Flags,
                                            DeclAttributes &Attributes);
-  ParserStatus parseInheritance(SmallVectorImpl<TypeLoc> &Inherited,
+  ParserStatus parseInheritance(SmallVectorImpl<InheritedEntry> &Inherited,
                                 bool allowClassRequirement,
                                 bool allowAnyObject);
   ParserStatus parseDeclItem(bool &PreviousHadSemi,

lib/AST/ASTContext.cpp

@@ -2188,7 +2188,8 @@ ASTContext::getConformance(Type conformingType,
                            ProtocolDecl *protocol,
                            SourceLoc loc,
                            DeclContext *dc,
-                           ProtocolConformanceState state) {
+                           ProtocolConformanceState state,
+                           bool isUnchecked) {
   assert(dc->isTypeContext());
 
   llvm::FoldingSetNodeID id;
@@ -2204,7 +2205,8 @@ ASTContext::getConformance(Type conformingType,
   // Build a new normal protocol conformance.
   auto result
     = new (*this, AllocationArena::Permanent)
-      NormalProtocolConformance(conformingType, protocol, loc, dc, state);
+        NormalProtocolConformance(
+          conformingType, protocol, loc, dc, state,isUnchecked);
   normalConformances.InsertNode(result, insertPos);
 
   return result;

lib/AST/ASTDumper.cpp

@@ -499,11 +499,12 @@ namespace {
         PrintWithColorRAII(OS, DeclModifierColor) << " trailing_semi";
     }
 
-    void printInherited(ArrayRef<TypeLoc> Inherited) {
+    void printInherited(ArrayRef<InheritedEntry> Inherited) {
       if (Inherited.empty())
         return;
       OS << " inherits: ";
-      interleave(Inherited, [&](TypeLoc Super) { Super.getType().print(OS); },
+      interleave(Inherited,
+                 [&](InheritedEntry Super) { Super.getType().print(OS); },
                  [&] { OS << ", "; });
     }