[APINotes] Allow annotating a C++ type as non-copyable in Swift

Certain C++ types, such as `std::chrono::tzdb` in libstdc++, are
non-copyable, but don't explicitly delete their copy constructor.
Instead, they trigger template instantiation errors when trying to call
their implicit copy constructor. The Swift compiler inserts implicit
copies of value types in some cases, which trigger compiler errors for
such types.

This adds a Clang API Notes attribute that allows annotating C++ types
as non-copyable in Swift. This lets the Swift compiler know that it
should not try to instantiate the implicit copy constructor for a C++
struct.

rdar://127049438

Author: egorzhdan

clang/include/clang/APINotes/Types.h

@@ -675,14 +675,21 @@ class TagInfo : public CommonTypeInfo {
   LLVM_PREFERRED_TYPE(bool)
   unsigned IsFlagEnum : 1;
 
+  LLVM_PREFERRED_TYPE(bool)
+  unsigned SwiftCopyableSpecified : 1;
+  LLVM_PREFERRED_TYPE(bool)
+  unsigned SwiftCopyable : 1;
+
 public:
   std::optional<std::string> SwiftImportAs;
   std::optional<std::string> SwiftRetainOp;
   std::optional<std::string> SwiftReleaseOp;
 
   std::optional<EnumExtensibilityKind> EnumExtensibility;
 
-  TagInfo() : HasFlagEnum(0), IsFlagEnum(0) {}
+  TagInfo()
+      : HasFlagEnum(0), IsFlagEnum(0), SwiftCopyableSpecified(false),
+        SwiftCopyable(false) {}
 
   std::optional<bool> isFlagEnum() const {
     if (HasFlagEnum)
@@ -694,6 +701,15 @@ class TagInfo : public CommonTypeInfo {
     IsFlagEnum = Value.value_or(false);
   }
 
+  std::optional<bool> isSwiftCopyable() const {
+    return SwiftCopyableSpecified ? std::optional<bool>(SwiftCopyable)
+                                  : std::nullopt;
+  }
+  void setSwiftCopyable(std::optional<bool> Value) {
+    SwiftCopyableSpecified = Value.has_value();
+    SwiftCopyable = Value.value_or(false);
+  }
+
   TagInfo &operator|=(const TagInfo &RHS) {
     static_cast<CommonTypeInfo &>(*this) |= RHS;
 
@@ -710,6 +726,9 @@ class TagInfo : public CommonTypeInfo {
     if (!EnumExtensibility)
       EnumExtensibility = RHS.EnumExtensibility;
 
+    if (!SwiftCopyableSpecified)
+      setSwiftCopyable(RHS.isSwiftCopyable());
+
     return *this;
   }
 
@@ -724,6 +743,7 @@ inline bool operator==(const TagInfo &LHS, const TagInfo &RHS) {
          LHS.SwiftRetainOp == RHS.SwiftRetainOp &&
          LHS.SwiftReleaseOp == RHS.SwiftReleaseOp &&
          LHS.isFlagEnum() == RHS.isFlagEnum() &&
+         LHS.isSwiftCopyable() == RHS.isSwiftCopyable() &&
          LHS.EnumExtensibility == RHS.EnumExtensibility;
 }
 

clang/lib/APINotes/APINotesFormat.h

@@ -24,7 +24,10 @@ const uint16_t VERSION_MAJOR = 0;
 /// API notes file minor version number.
 ///
 /// When the format changes IN ANY WAY, this number should be incremented.
-const uint16_t VERSION_MINOR = 25; // SwiftImportAs
+const uint16_t VERSION_MINOR = 26; // SwiftCopyable
+
+const uint8_t kSwiftCopyable = 1;
+const uint8_t kSwiftNonCopyable = 2;
 
 using IdentifierID = llvm::PointerEmbeddedInt<unsigned, 31>;
 using IdentifierIDField = llvm::BCVBR<16>;

clang/lib/APINotes/APINotesReader.cpp

@@ -527,6 +527,13 @@ class TagTableInfo
       Info.EnumExtensibility =
           static_cast<EnumExtensibilityKind>((Payload & 0x3) - 1);
 
+    uint8_t Copyable =
+        endian::readNext<uint8_t, llvm::endianness::little>(Data);
+    if (Copyable == kSwiftNonCopyable)
+      Info.setSwiftCopyable(std::optional(false));
+    else if (Copyable == kSwiftCopyable)
+      Info.setSwiftCopyable(std::optional(true));
+
     unsigned ImportAsLength =
         endian::readNext<uint16_t, llvm::endianness::little>(Data);
     if (ImportAsLength > 0) {

clang/lib/APINotes/APINotesWriter.cpp

@@ -1128,7 +1128,7 @@ class TagTableInfo : public CommonTypeTableInfo<TagTableInfo, TagInfo> {
     return 2 + (TI.SwiftImportAs ? TI.SwiftImportAs->size() : 0) +
            2 + (TI.SwiftRetainOp ? TI.SwiftRetainOp->size() : 0) +
            2 + (TI.SwiftReleaseOp ? TI.SwiftReleaseOp->size() : 0) +
-           1 + getCommonTypeInfoSize(TI);
+           2 + getCommonTypeInfoSize(TI);
   }
 
   void emitUnversionedInfo(raw_ostream &OS, const TagInfo &TI) {
@@ -1146,6 +1146,11 @@ class TagTableInfo : public CommonTypeTableInfo<TagTableInfo, TagInfo> {
 
     writer.write<uint8_t>(Flags);
 
+    if (auto Copyable = TI.isSwiftCopyable())
+      writer.write<uint8_t>(*Copyable ? kSwiftCopyable : kSwiftNonCopyable);
+    else
+      writer.write<uint8_t>(0);
+
     if (auto ImportAs = TI.SwiftImportAs) {
       writer.write<uint16_t>(ImportAs->size() + 1);
       OS.write(ImportAs->c_str(), ImportAs->size());

clang/lib/APINotes/APINotesYAMLCompiler.cpp

@@ -419,6 +419,7 @@ struct Tag {
   std::optional<EnumExtensibilityKind> EnumExtensibility;
   std::optional<bool> FlagEnum;
   std::optional<EnumConvenienceAliasKind> EnumConvenienceKind;
+  std::optional<bool> SwiftCopyable;
 };
 
 typedef std::vector<Tag> TagsSeq;
@@ -452,6 +453,7 @@ template <> struct MappingTraits<Tag> {
     IO.mapOptional("EnumExtensibility", T.EnumExtensibility);
     IO.mapOptional("FlagEnum", T.FlagEnum);
     IO.mapOptional("EnumKind", T.EnumConvenienceKind);
+    IO.mapOptional("SwiftCopyable", T.SwiftCopyable);
   }
 };
 } // namespace yaml
@@ -1009,6 +1011,9 @@ class YAMLConverter {
       if (Tag.SwiftReleaseOp)
         TI.SwiftReleaseOp = Tag.SwiftReleaseOp;
 
+      if (Tag.SwiftCopyable)
+        TI.setSwiftCopyable(Tag.SwiftCopyable);
+
       if (Tag.EnumConvenienceKind) {
         if (Tag.EnumExtensibility) {
           emitError(

clang/lib/Sema/SemaAPINotes.cpp

@@ -594,6 +594,11 @@ static void ProcessAPINotes(Sema &S, TagDecl *D, const api_notes::TagInfo &Info,
     D->addAttr(
         SwiftAttrAttr::Create(S.Context, "release:" + ReleaseOp.value()));
 
+  if (auto Copyable = Info.isSwiftCopyable()) {
+    if (!*Copyable)
+      D->addAttr(SwiftAttrAttr::Create(S.Context, "~Copyable"));
+  }
+
   if (auto Extensibility = Info.EnumExtensibility) {
     using api_notes::EnumExtensibilityKind;
     bool ShouldAddAttribute = (*Extensibility != EnumExtensibilityKind::None);

clang/test/APINotes/Inputs/Headers/SwiftImportAs.apinotes

@@ -7,3 +7,7 @@ Tags:
   SwiftImportAs: reference
   SwiftReleaseOp: RCRelease
   SwiftRetainOp: RCRetain
+- Name: NonCopyableType
+  SwiftCopyable: false
+- Name: CopyableType
+  SwiftCopyable: true

clang/test/APINotes/Inputs/Headers/SwiftImportAs.h

@@ -4,3 +4,6 @@ struct RefCountedType { int value; };
 
 inline void RCRetain(RefCountedType *x) { x->value++; }
 inline void RCRelease(RefCountedType *x) { x->value--; }
+
+struct NonCopyableType { int value; };
+struct CopyableType { int value; };

clang/test/APINotes/swift-import-as.cpp

@@ -2,6 +2,8 @@
 // RUN: %clang_cc1 -fmodules -fblocks -fimplicit-module-maps -fmodules-cache-path=%t/ModulesCache -fdisable-module-hash -fapinotes-modules -fsyntax-only -I %S/Inputs/Headers %s -x c++
 // RUN: %clang_cc1 -fmodules -fblocks -fimplicit-module-maps -fmodules-cache-path=%t/ModulesCache -fdisable-module-hash -fapinotes-modules -fsyntax-only -I %S/Inputs/Headers %s -x c++ -ast-dump -ast-dump-filter ImmortalRefType | FileCheck -check-prefix=CHECK-IMMORTAL %s
 // RUN: %clang_cc1 -fmodules -fblocks -fimplicit-module-maps -fmodules-cache-path=%t/ModulesCache -fdisable-module-hash -fapinotes-modules -fsyntax-only -I %S/Inputs/Headers %s -x c++ -ast-dump -ast-dump-filter RefCountedType | FileCheck -check-prefix=CHECK-REF-COUNTED %s
+// RUN: %clang_cc1 -fmodules -fblocks -fimplicit-module-maps -fmodules-cache-path=%t/ModulesCache -fdisable-module-hash -fapinotes-modules -fsyntax-only -I %S/Inputs/Headers %s -x c++ -ast-dump -ast-dump-filter NonCopyableType | FileCheck -check-prefix=CHECK-NON-COPYABLE %s
+// RUN: %clang_cc1 -fmodules -fblocks -fimplicit-module-maps -fmodules-cache-path=%t/ModulesCache -fdisable-module-hash -fapinotes-modules -fsyntax-only -I %S/Inputs/Headers %s -x c++ -ast-dump -ast-dump-filter CopyableType | FileCheck -check-prefix=CHECK-COPYABLE %s
 
 #include <SwiftImportAs.h>
 
@@ -14,3 +16,11 @@
 // CHECK-REF-COUNTED: SwiftAttrAttr {{.+}} <<invalid sloc>> "import_reference"
 // CHECK-REF-COUNTED: SwiftAttrAttr {{.+}} <<invalid sloc>> "retain:RCRetain"
 // CHECK-REF-COUNTED: SwiftAttrAttr {{.+}} <<invalid sloc>> "release:RCRelease"
+
+// CHECK-NON-COPYABLE: Dumping NonCopyableType:
+// CHECK-NON-COPYABLE-NEXT: CXXRecordDecl {{.+}} imported in SwiftImportAs {{.+}} struct NonCopyableType
+// CHECK-NON-COPYABLE: SwiftAttrAttr {{.+}} <<invalid sloc>> "~Copyable"
+
+// CHECK-COPYABLE: Dumping CopyableType:
+// CHECK-COPYABLE-NEXT: CXXRecordDecl {{.+}} imported in SwiftImportAs {{.+}} struct CopyableType
+// CHECK-COPYABLE-NOT: SwiftAttrAttr