[SE-0302] Implement structural conformances to Sendable.

include/swift/AST/ASTContext.h

@@ -105,6 +105,7 @@ namespace swift {
   class InheritedProtocolConformance;
   class SelfProtocolConformance;
   class SpecializedProtocolConformance;
+  class BuiltinProtocolConformance;
   enum class ProtocolConformanceState;
   class Pattern;
   enum PointerTypeKind : unsigned;
@@ -1029,6 +1030,12 @@ class ASTContext final {
   SelfProtocolConformance *
   getSelfConformance(ProtocolDecl *protocol);
 
+  /// Produce the builtin conformance for some structural type to some protocol.
+  BuiltinProtocolConformance *
+  getBuiltinConformance(Type type, ProtocolDecl *protocol,
+                        GenericSignature genericSig,
+                        ArrayRef<Requirement> conditionalRequirements);
+
   /// A callback used to produce a diagnostic for an ill-formed protocol
   /// conformance that was type-checked before we're actually walking the
   /// conformance itself, along with a bit indicating whether this diagnostic

include/swift/AST/DiagnosticsSema.def

@@ -1923,6 +1923,12 @@ ERROR(type_cannot_conform, none,
 NOTE(only_concrete_types_conform_to_protocols,none,
      "only concrete types such as structs, enums and classes can conform to protocols",
      ())
+NOTE(nonsendable_function_type,none,
+     "a function type must be marked '@Sendable' to conform to 'Sendable'", ())
+NOTE(nonsendable_tuple_type,none,
+     "a tuple type must be composed of 'Sendable' elements to conform to "
+     "'Sendable'", ())
+
 NOTE(required_by_opaque_return,none,
     "required by opaque return type of %0 %1", (DescriptiveDeclKind, DeclName))
 NOTE(required_by_decl,none,

include/swift/AST/ProtocolConformance.h

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -66,7 +66,10 @@ enum class ProtocolConformanceKind {
   Specialized,
   /// Conformance of a generic class type projected through one of its
   /// superclass's conformances.
-  Inherited
+  Inherited,
+  /// Builtin conformances are special conformaces that the runtime handles
+  /// and isn't implemented directly in Swift.
+  Builtin
 };
 
 /// Describes the state of a protocol conformance, which may be complete,
@@ -329,7 +332,9 @@ class alignas(1 << DeclAlignInBits) ProtocolConformance {
 /// - the type is directly declared to conform to the protocol (a
 ///   normal conformance) or
 /// - the protocol's existential type is known to conform to itself (a
-///   self-conformance).
+///   self-conformance) or
+/// - the type's conformance is declared within the runtime (a builtin
+///   conformance).
 class RootProtocolConformance : public ProtocolConformance {
 protected:
   RootProtocolConformance(ProtocolConformanceKind kind, Type conformingType)
@@ -380,7 +385,8 @@ class RootProtocolConformance : public ProtocolConformance {
 
   static bool classof(const ProtocolConformance *conformance) {
     return conformance->getKind() == ProtocolConformanceKind::Normal ||
-           conformance->getKind() == ProtocolConformanceKind::Self;
+           conformance->getKind() == ProtocolConformanceKind::Self ||
+           conformance->getKind() == ProtocolConformanceKind::Builtin;
   }
 };
 
@@ -987,6 +993,103 @@ class InheritedProtocolConformance : public ProtocolConformance,
   }
 };
 
+/// A builtin conformance appears when a non-nominal type has a
+/// conformance that is synthesized by the implementation.
+class BuiltinProtocolConformance final : public RootProtocolConformance,
+      private llvm::TrailingObjects<BuiltinProtocolConformance, Requirement> {
+  friend ASTContext;
+  friend TrailingObjects;
+
+  ProtocolDecl *protocol;
+  GenericSignature genericSig;
+  size_t numConditionalRequirements;
+
+  size_t numTrailingObjects(OverloadToken<Requirement>) const {
+    return numConditionalRequirements;
+  }
+
+  BuiltinProtocolConformance(Type conformingType, ProtocolDecl *protocol,
+                             GenericSignature genericSig,
+                             ArrayRef<Requirement> conditionalRequirements);
+
+public:
+  /// Get the protocol being conformed to.
+  ProtocolDecl *getProtocol() const {
+    return protocol;
+  }
+
+  /// Retrieve the generic signature that describes the type parameters used
+  /// within the conforming type.
+  GenericSignature getGenericSignature() const {
+    return genericSig;
+  }
+
+  /// Get any requirements that must be satisfied for this conformance to apply.
+  Optional<ArrayRef<Requirement>>
+  getConditionalRequirementsIfAvailable() const {
+    return getConditionalRequirements();
+  }
+
+  /// Get any requirements that must be satisfied for this conformance to apply.
+  ArrayRef<Requirement> getConditionalRequirements() const {
+    return {getTrailingObjects<Requirement>(), numConditionalRequirements};
+  }
+
+  /// Get the declaration context that contains the nominal type declaration.
+  DeclContext *getDeclContext() const {
+    return getProtocol();
+  }
+
+  /// Retrieve the state of this conformance.
+  ProtocolConformanceState getState() const {
+    return ProtocolConformanceState::Complete;
+  }
+
+  /// Get the kind of source from which this conformance comes.
+  ConformanceEntryKind getSourceKind() const {
+    return ConformanceEntryKind::Synthesized;
+  }
+  /// Get the protocol conformance which implied this implied conformance.
+  NormalProtocolConformance *getImplyingConformance() const {
+    return nullptr;
+  }
+
+  bool hasTypeWitness(AssociatedTypeDecl *assocType) const {
+    llvm_unreachable("builtin-conformances never have associated types");
+  }
+
+  /// Retrieve the type witness and type decl (if one exists)
+  /// for the given associated type.
+  TypeWitnessAndDecl
+  getTypeWitnessAndDecl(AssociatedTypeDecl *assocType,
+                        SubstOptions options=None) const {
+    llvm_unreachable("builtin-conformances never have associated types");
+  }
+
+  /// Given that the requirement signature of the protocol directly states
+  /// that the given dependent type must conform to the given protocol,
+  /// return its associated conformance.
+  ProtocolConformanceRef
+  getAssociatedConformance(Type assocType, ProtocolDecl *protocol) const {
+    llvm_unreachable("builtin-conformances never have associated types");
+  }
+
+  /// Retrieve the witness corresponding to the given value requirement.
+  ConcreteDeclRef getWitnessDeclRef(ValueDecl *requirement) const {
+    return ConcreteDeclRef(requirement);
+  }
+
+  /// Determine whether the witness for the given requirement
+  /// is either the default definition or was otherwise deduced.
+  bool usesDefaultDefinition(AssociatedTypeDecl *requirement) const {
+    llvm_unreachable("builtin-conformances never have associated types");
+  }
+
+  static bool classof(const ProtocolConformance *conformance) {
+    return conformance->getKind() == ProtocolConformanceKind::Builtin;
+  }
+};
+
 inline bool ProtocolConformance::isInvalid() const {
   return getRootConformance()->isInvalid();
 }

lib/AST/ASTContext.cpp

@@ -439,6 +439,10 @@ struct ASTContext::Implementation {
     /// The set of inherited protocol conformances.
     llvm::FoldingSet<InheritedProtocolConformance> InheritedConformances;
 
+    /// The set of builtin protocol conformances.
+    llvm::DenseMap<std::pair<Type, ProtocolDecl *>,
+                   BuiltinProtocolConformance *> BuiltinConformances;
+
     /// The set of substitution maps (uniqued by their storage).
     llvm::FoldingSet<SubstitutionMap::Storage> SubstitutionMaps;
 
@@ -2243,6 +2247,28 @@ ASTContext::getSelfConformance(ProtocolDecl *protocol) {
   return entry;
 }
 
+/// Produce the builtin conformance for some non-nominal to some protocol.
+BuiltinProtocolConformance *
+ASTContext::getBuiltinConformance(
+    Type type, ProtocolDecl *protocol,
+    GenericSignature genericSig,
+    ArrayRef<Requirement> conditionalRequirements
+) {
+  auto key = std::make_pair(type, protocol);
+  AllocationArena arena = getArena(type->getRecursiveProperties());
+  auto &builtinConformances = getImpl().getArena(arena).BuiltinConformances;
+
+  auto &entry = builtinConformances[key];
+  if (!entry) {
+    auto size = BuiltinProtocolConformance::
+        totalSizeToAlloc<Requirement>(conditionalRequirements.size());
+    auto mem = this->Allocate(size, alignof(BuiltinProtocolConformance), arena);
+    entry = new (mem) BuiltinProtocolConformance(
+        type, protocol, genericSig, conditionalRequirements);
+  }
+  return entry;
+}
+
 /// If one of the ancestor conformances already has a matching type, use
 /// that instead.
 static ProtocolConformance *collapseSpecializedConformance(
@@ -2259,6 +2285,7 @@ static ProtocolConformance *collapseSpecializedConformance(
     case ProtocolConformanceKind::Normal:
     case ProtocolConformanceKind::Inherited:
     case ProtocolConformanceKind::Self:
+    case ProtocolConformanceKind::Builtin:
       // If the conformance matches, return it.
       if (conformance->getType()->isEqual(type)) {
         for (auto subConformance : substitutions.getConformances())
@@ -2496,6 +2523,7 @@ size_t ASTContext::Implementation::Arena::getTotalMemory() const {
     // NormalConformances ?
     // SpecializedConformances ?
     // InheritedConformances ?
+    // BuiltinConformances ?
 }
 
 void AbstractFunctionDecl::setForeignErrorConvention(

lib/AST/ASTDumper.cpp

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -3262,6 +3262,10 @@ static void dumpProtocolConformanceRec(
                                visited);
     break;
   }
+
+  case ProtocolConformanceKind::Builtin: {
+    printCommon("builtin");
+  }
   }
 
   PrintWithColorRAII(out, ParenthesisColor) << ')';

lib/AST/ASTMangler.cpp

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -209,9 +209,11 @@ std::string ASTMangler::mangleWitnessTable(const RootProtocolConformance *C) {
   if (isa<NormalProtocolConformance>(C)) {
     appendProtocolConformance(C);
     appendOperator("WP");
-  } else {
+  } else if (isa<SelfProtocolConformance>(C)) {
     appendProtocolName(cast<SelfProtocolConformance>(C)->getProtocol());
     appendOperator("WS");
+  } else {
+    llvm_unreachable("mangling unknown conformance kind");
   }
   return finalize();
 }
@@ -235,7 +237,11 @@ std::string ASTMangler::mangleWitnessThunk(
   }
 
   if (Conformance) {
-    appendOperator(isa<SelfProtocolConformance>(Conformance) ? "TS" : "TW");
+    if (isa<SelfProtocolConformance>(Conformance)) {
+      appendOperator("TS");
+    } else {
+      appendOperator("TW");
+    }
   }
   return finalize();
 }
@@ -1556,7 +1562,8 @@ void ASTMangler::appendBoundGenericArgs(Type type, bool &isFirstArgList) {
 static bool conformanceHasIdentity(const RootProtocolConformance *root) {
   auto conformance = dyn_cast<NormalProtocolConformance>(root);
   if (!conformance) {
-    assert(isa<SelfProtocolConformance>(root));
+    assert(isa<SelfProtocolConformance>(root) ||
+           isa<BuiltinProtocolConformance>(root));
     return true;
   }
 
@@ -1577,8 +1584,9 @@ static bool conformanceHasIdentity(const RootProtocolConformance *root) {
 static bool isRetroactiveConformance(const RootProtocolConformance *root) {
   auto conformance = dyn_cast<NormalProtocolConformance>(root);
   if (!conformance) {
-    assert(isa<SelfProtocolConformance>(root));
-    return false; // self-conformances are never retroactive.
+    assert(isa<SelfProtocolConformance>(root) ||
+           isa<BuiltinProtocolConformance>(root));
+    return false; // self-conformances are never retroactive. nor are builtin.
   }
 
   return conformance->isRetroactive();
@@ -3058,6 +3066,10 @@ ASTMangler::appendProtocolConformance(const ProtocolConformance *conformance) {
     appendModule(Mod, DC->getAsDecl()->getAlternateModuleName());
   }
 
+  // If this is a non-nominal type, we're done.
+  if (!conformingType->getAnyNominal())
+    return;
+
   contextSig =
     conformingType->getAnyNominal()->getGenericSignatureOfContext();
 
@@ -3082,6 +3094,9 @@ void ASTMangler::appendProtocolConformanceRef(
     assert(DC->getAsDecl());
     appendModule(conformance->getDeclContext()->getParentModule(),
                  DC->getAsDecl()->getAlternateModuleName());
+  // Builtin conformances are always from the Swift module.
+  } else if (isa<BuiltinProtocolConformance>(conformance)) {
+    appendOperator("HP");
   } else if (conformance->getDeclContext()->getParentModule() ==
                conformance->getType()->getAnyNominal()->getParentModule()) {
     appendOperator("HP");

lib/AST/ASTPrinter.cpp

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -5699,6 +5699,12 @@ void ProtocolConformance::printName(llvm::raw_ostream &os,
     os << ")";
     break;
   }
+  case ProtocolConformanceKind::Builtin: {
+    auto builtin = cast<BuiltinProtocolConformance>(this);
+    os << builtin->getProtocol()->getName()
+       << " type " << builtin->getType();
+    break;
+  }
   }
 }