AST: Add an IsForEmbedded bit to AvailableAttr.

This bit is true for attributes written as `@_unavailableInEmbedded` in source.

Author: tshortli

include/swift/AST/Attr.h

@@ -147,9 +147,12 @@ class DeclAttribute : public AttributeBase {
       Value : 32
     );
 
-    SWIFT_INLINE_BITFIELD(AvailableAttr, DeclAttribute, 1,
+    SWIFT_INLINE_BITFIELD(AvailableAttr, DeclAttribute, 1+1,
       /// Whether this attribute was spelled `@_spi_available`.
-      IsSPI : 1
+      IsSPI : 1,
+
+      /// Whether this attribute was spelled `@_unavailableInEmbedded`.
+      IsForEmbedded : 1
     );
 
     SWIFT_INLINE_BITFIELD(ClangImporterSynthesizedTypeAttr, DeclAttribute, 1,
@@ -679,8 +682,6 @@ enum class PlatformAgnosticAvailabilityKind {
 /// Defines the @available attribute.
 class AvailableAttr : public DeclAttribute {
 public:
-#define INIT_VER_TUPLE(X) X(X.empty() ? std::optional<llvm::VersionTuple>() : X)
-
   AvailableAttr(SourceLoc AtLoc, SourceRange Range, PlatformKind Platform,
                 StringRef Message, StringRef Rename, ValueDecl *RenameDecl,
                 const llvm::VersionTuple &Introduced,
@@ -689,17 +690,7 @@ class AvailableAttr : public DeclAttribute {
                 SourceRange DeprecatedRange,
                 const llvm::VersionTuple &Obsoleted, SourceRange ObsoletedRange,
                 PlatformAgnosticAvailabilityKind PlatformAgnostic,
-                bool Implicit, bool IsSPI)
-      : DeclAttribute(DeclAttrKind::Available, AtLoc, Range, Implicit),
-        Message(Message), Rename(Rename), RenameDecl(RenameDecl),
-        INIT_VER_TUPLE(Introduced), IntroducedRange(IntroducedRange),
-        INIT_VER_TUPLE(Deprecated), DeprecatedRange(DeprecatedRange),
-        INIT_VER_TUPLE(Obsoleted), ObsoletedRange(ObsoletedRange),
-        PlatformAgnostic(PlatformAgnostic), Platform(Platform) {
-    Bits.AvailableAttr.IsSPI = IsSPI;
-  }
-
-#undef INIT_VER_TUPLE
+                bool Implicit, bool IsSPI, bool IsForEmbedded = false);
 
   /// The optional message.
   const StringRef Message;
@@ -760,6 +751,9 @@ class AvailableAttr : public DeclAttribute {
   /// Whether this attribute was spelled `@_spi_available`.
   bool isSPI() const { return Bits.AvailableAttr.IsSPI; }
 
+  /// Whether this attribute was spelled `@_unavailableInEmbedded`.
+  bool isForEmbedded() const { return Bits.AvailableAttr.IsForEmbedded; }
+
   /// Returns the platform-agnostic availability.
   PlatformAgnosticAvailabilityKind getPlatformAgnosticAvailability() const {
     return PlatformAgnostic;

include/swift/Strings.h

@@ -85,6 +85,10 @@ constexpr static const StringLiteral CLANG_MODULE_DEFAULT_SPI_GROUP_NAME =
 constexpr static const StringLiteral SPI_AVAILABLE_ATTRNAME =
   "_spi_available";
 
+/// The attribute name for @_unavailableInEmbedded
+constexpr static const StringLiteral UNAVAILABLE_IN_EMBEDDED_ATTRNAME =
+    "_unavailableInEmbedded";
+
 /// A composition class containing a StringLiteral for the names of
 /// Swift builtins. The reason we use this is to ensure that we when
 /// necessary slice off the "Builtin." prefix from these names in a

lib/AST/Attr.cpp

@@ -1380,6 +1380,13 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
       Printer << ", unavailable)";
       break;
     }
+    if (Attr->isForEmbedded()) {
+      std::string atUnavailableInEmbedded =
+          (llvm::Twine("@") + UNAVAILABLE_IN_EMBEDDED_ATTRNAME).str();
+      Printer.printAttrName(atUnavailableInEmbedded);
+      break;
+    }
+
     if (Attr->isSPI()) {
       std::string atSPI = (llvm::Twine("@") + SPI_AVAILABLE_ATTRNAME).str();
       Printer.printAttrName(atSPI);
@@ -2243,6 +2250,34 @@ Type RawLayoutAttr::getResolvedCountType(StructDecl *sd) const {
                            ErrorType::get(ctx));
 }
 
+#define INIT_VER_TUPLE(X) X(X.empty() ? std::optional<llvm::VersionTuple>() : X)
+
+AvailableAttr::AvailableAttr(
+    SourceLoc AtLoc, SourceRange Range, PlatformKind Platform,
+    StringRef Message, StringRef Rename, ValueDecl *RenameDecl,
+    const llvm::VersionTuple &Introduced, SourceRange IntroducedRange,
+    const llvm::VersionTuple &Deprecated, SourceRange DeprecatedRange,
+    const llvm::VersionTuple &Obsoleted, SourceRange ObsoletedRange,
+    PlatformAgnosticAvailabilityKind PlatformAgnostic, bool Implicit,
+    bool IsSPI, bool IsForEmbedded)
+    : DeclAttribute(DeclAttrKind::Available, AtLoc, Range, Implicit),
+      Message(Message), Rename(Rename), RenameDecl(RenameDecl),
+      INIT_VER_TUPLE(Introduced), IntroducedRange(IntroducedRange),
+      INIT_VER_TUPLE(Deprecated), DeprecatedRange(DeprecatedRange),
+      INIT_VER_TUPLE(Obsoleted), ObsoletedRange(ObsoletedRange),
+      PlatformAgnostic(PlatformAgnostic), Platform(Platform) {
+  Bits.AvailableAttr.IsSPI = IsSPI;
+
+  if (IsForEmbedded) {
+    // FIXME: The IsForEmbedded bit should be removed when library availability
+    // conditions are implemented (rdar://138802876)
+    Bits.AvailableAttr.IsForEmbedded = true;
+    assert(Platform == PlatformKind::none);
+  }
+}
+
+#undef INIT_VER_TUPLE
+
 AvailableAttr *
 AvailableAttr::createPlatformAgnostic(ASTContext &C,
                                    StringRef Message,
@@ -2294,7 +2329,8 @@ AvailableAttr *AvailableAttr::clone(ASTContext &C, bool implicit) const {
                                implicit ? SourceRange() : ObsoletedRange,
                                PlatformAgnostic,
                                implicit,
-                               isSPI());
+                               isSPI(),
+                               isForEmbedded());
 }
 
 std::optional<OriginallyDefinedInAttr::ActiveVersion>

lib/Parse/ParseDecl.cpp

@@ -4501,18 +4501,16 @@ ParserStatus Parser::parseDeclAttribute(DeclAttributes &Attributes,
 
   // Rewrite @_unavailableInEmbedded into @available(*, unavailable) when in
   // embedded Swift mode, or into nothing when in regular mode.
-  if (!DK && Tok.getText() == "_unavailableInEmbedded") {
+  if (!DK && Tok.getText() == UNAVAILABLE_IN_EMBEDDED_ATTRNAME) {
     SourceLoc attrLoc = consumeToken();
     if (Context.LangOpts.hasFeature(Feature::Embedded)) {
       StringRef Message = "unavailable in embedded Swift", Renamed;
-      auto attr = new (Context) AvailableAttr(AtLoc, SourceRange(AtLoc, attrLoc),
-                  PlatformKind::none,
-                  Message, Renamed, /*RenameDecl=*/nullptr,
-                  llvm::VersionTuple(), SourceRange(),
-                  llvm::VersionTuple(), SourceRange(),
-                  llvm::VersionTuple(), SourceRange(),
-                  PlatformAgnosticAvailabilityKind::Unavailable,
-                  /*Implicit=*/false, /*IsSPI=*/false);
+      auto attr = new (Context) AvailableAttr(
+          AtLoc, SourceRange(AtLoc, attrLoc), PlatformKind::none, Message,
+          Renamed, /*RenameDecl=*/nullptr, llvm::VersionTuple(), SourceRange(),
+          llvm::VersionTuple(), SourceRange(), llvm::VersionTuple(),
+          SourceRange(), PlatformAgnosticAvailabilityKind::Unavailable,
+          /*Implicit=*/false, /*IsSPI=*/false, /*IsForEmbedded=*/true);
       Attributes.add(attr);
     }
     return makeParserSuccess();

test/attr/attr_unavailable_in_embedded.swift

@@ -0,0 +1,13 @@
+// RUN: %target-swift-frontend -typecheck %s -parse-stdlib -print-ast | %FileCheck %s --check-prefix=CHECK-NON-EMBEDDED
+// RUN: %target-swift-frontend -typecheck %s -parse-stdlib -enable-experimental-feature Embedded -print-ast | %FileCheck %s --check-prefix=CHECK-EMBEDDED
+
+// CHECK-NON-EMBEDDED-NOT: @available
+// CHECK-NON-EMBEDDED-NOT: @_unavailableInEmbedded
+// CHECK-NON-EMBEDDED:     public func unavailable()
+
+// CHECK-EMBEDDED-NOT:  @available
+// CHECK-EMBEDDED:      @_unavailableInEmbedded
+// CHECK-EMBEDDED-NEXT: public func unavailable()
+
+@_unavailableInEmbedded
+public func unavailable() {}