Add @_private(from: "SourceFile.swift") imports

A module compiled with `-enable-private-imports` allows other modules to
import private declarations if the importing source file uses an
``@_private(from: "SourceFile.swift") import statement.

rdar://29318654

Author: aschwaighofer

include/swift/AST/Attr.def

@@ -384,6 +384,10 @@ DECL_ATTR(_dynamicReplacement, DynamicReplacement,
 SIMPLE_DECL_ATTR(_borrowed, Borrowed,
   OnVar | OnSubscript | UserInaccessible |
   NotSerialized, 81)
+DECL_ATTR(_private, PrivateImport,
+  OnImport |
+  UserInaccessible |
+  NotSerialized, 82)
 
 #undef TYPE_ATTR
 #undef DECL_ATTR_ALIAS

include/swift/AST/Attr.h

@@ -901,6 +901,26 @@ class ObjCAttr final : public DeclAttribute,
   }
 };
 
+class PrivateImportAttr final
+: public DeclAttribute {
+  StringRef SourceFile;
+
+  PrivateImportAttr(SourceLoc atLoc, SourceRange baseRange,
+                    StringRef sourceFile, SourceRange parentRange);
+
+public:
+  static PrivateImportAttr *create(ASTContext &Ctxt, SourceLoc AtLoc,
+                                   SourceLoc PrivateLoc, SourceLoc LParenLoc,
+                                   StringRef sourceFile, SourceLoc RParenLoc);
+
+  StringRef getSourceFile() const {
+    return SourceFile;
+  }
+  static bool classof(const DeclAttribute *DA) {
+    return DA->getKind() == DAK_PrivateImport;
+  }
+};
+
 /// The @_dynamicReplacement(for:) attribute.
 class DynamicReplacementAttr final
     : public DeclAttribute,

include/swift/AST/Decl.h

@@ -573,7 +573,7 @@ class alignas(1 << DeclAlignInBits) Decl {
     HasAnyUnavailableValues : 1
   );
 
-  SWIFT_INLINE_BITFIELD(ModuleDecl, TypeDecl, 1+1+1+1,
+  SWIFT_INLINE_BITFIELD(ModuleDecl, TypeDecl, 1+1+1+1+1,
     /// If the module was or is being compiled with `-enable-testing`.
     TestingEnabled : 1,
 
@@ -586,7 +586,10 @@ class alignas(1 << DeclAlignInBits) Decl {
     RawResilienceStrategy : 1,
 
     /// Whether all imports have been resolved. Used to detect circular imports.
-    HasResolvedImports : 1
+    HasResolvedImports : 1,
+
+    // If the module was or is being compiled with `-enable-private-imports`.
+    PrivateImportsEnabled : 1
   );
 
   SWIFT_INLINE_BITFIELD(PrecedenceGroupDecl, Decl, 1+2,

include/swift/AST/DiagnosticsParse.def

@@ -1417,6 +1417,15 @@ ERROR(attr_dynamic_replacement_expected_for,none,
 ERROR(attr_dynamic_replacement_expected_colon,none,
       "expected ':' after @_dynamicReplacement(for", ())
 
+ERROR(attr_private_import_expected_rparen,none,
+      "expected ')' after function name for @_private", ())
+ERROR(attr_private_import_expected_sourcefile, none,
+      "expected 'sourceFile' in '_private' attribute", ())
+ERROR(attr_private_import_expected_sourcefile_name,none,
+      "expected a source file name in @_private(sourceFile:)", ())
+ERROR(attr_private_import_expected_colon,none,
+      "expected ':' after @_private(sourceFile", ())
+
 // opened
 ERROR(opened_attribute_expected_lparen,none,
       "expected '(' after 'opened' attribute", ())

include/swift/AST/DiagnosticsSema.def

@@ -759,6 +759,10 @@ ERROR(ambiguous_decl_in_module,none,
 ERROR(module_not_testable,none,
       "module %0 was not compiled for testing", (Identifier))
 
+ERROR(module_not_compiled_for_private_import,none,
+      "module %0 was not compiled for private import", (Identifier))
+
+
 // Operator decls
 ERROR(ambiguous_operator_decls,none,
       "ambiguous operator declarations found for operator", ())

include/swift/AST/Module.h

@@ -283,6 +283,15 @@ class ModuleDecl : public DeclContext, public TypeDecl {
     Bits.ModuleDecl.TestingEnabled = enabled;
   }
 
+  /// Returns true if this module was or is begin compile with
+  /// `-enable-private-imports`.
+  bool arePrivateImportsEnabled() const {
+    return Bits.ModuleDecl.PrivateImportsEnabled;
+  }
+  void setPrivateImportsEnabled(bool enabled = true) {
+    Bits.ModuleDecl.PrivateImportsEnabled = true;
+  }
+
   /// Returns true if there was an error trying to load this module.
   bool failedToLoad() const {
     return Bits.ModuleDecl.FailedToLoad;
@@ -844,7 +853,11 @@ class SourceFile final : public FileUnit {
 
     /// This source file has access to testable declarations in the imported
     /// module.
-    Testable = 0x2
+    Testable = 0x2,
+
+    /// This source file has access to private declarations in the imported
+    /// moduled.
+    PrivateImport = 0x4,
   };
 
   /// \see ImportFlags
@@ -857,7 +870,9 @@ class SourceFile final : public FileUnit {
   /// This is the list of modules that are imported by this module.
   ///
   /// This is filled in by the Name Binding phase.
-  ArrayRef<std::pair<ModuleDecl::ImportedModule, ImportOptions>> Imports;
+  ArrayRef<std::pair<ModuleDecl::ImportedModule,
+                     std::pair<ImportOptions, StringRef>>>
+      Imports;
 
   /// A unique identifier representing this file; used to mark private decls
   /// within the file to keep them from conflicting with other files in the
@@ -961,11 +976,14 @@ class SourceFile final : public FileUnit {
              ImplicitModuleImportKind ModImpKind, bool KeepParsedTokens = false,
              bool KeepSyntaxTree = false);
 
-  void
-  addImports(ArrayRef<std::pair<ModuleDecl::ImportedModule, ImportOptions>> IM);
+  void addImports(ArrayRef<std::pair<ModuleDecl::ImportedModule,
+                                     std::pair<ImportOptions, StringRef>>>
+                      IM);
 
   bool hasTestableImport(const ModuleDecl *module) const;
 
+  bool hasPrivateImport(AccessLevel accessLevel, const ValueDecl *ofDecl) const;
+
   void clearLookupCache();
 
   void cacheVisibleDecls(SmallVectorImpl<ValueDecl *> &&globals) const;
@@ -1224,12 +1242,29 @@ class LoadedFile : public FileUnit {
     assert(classof(this) && "invalid kind");
   }
 
+  /// A map from private/fileprivate decls to the file they were defined in.
+  llvm::DenseMap<const ValueDecl *, Identifier> FilenameForPrivateDecls;
+
 public:
+
   /// Returns an arbitrary string representing the storage backing this file.
   ///
   /// This is usually a filesystem path.
   virtual StringRef getFilename() const;
 
+  void addFilenameForPrivateDecl(const ValueDecl *decl, Identifier id) {
+    assert(!FilenameForPrivateDecls.count(decl) ||
+           FilenameForPrivateDecls[decl] == id);
+    FilenameForPrivateDecls[decl] = id;
+  }
+
+  StringRef getFilenameForPrivateDecl(const ValueDecl *decl) {
+    auto it = FilenameForPrivateDecls.find(decl);
+    if (it == FilenameForPrivateDecls.end())
+      return StringRef();
+    else return it->second.str();
+  }
+
   /// Look up an operator declaration.
   ///
   /// \param name The operator name ("+", ">>", etc.)

include/swift/Frontend/FrontendOptions.h

@@ -192,6 +192,11 @@ class FrontendOptions {
   /// \see ModuleDecl::isTestingEnabled
   bool EnableTesting = false;
 
+  /// Indicates whether we are compiling for testing.
+  ///
+  /// \see ModuleDecl::arePrivateImportsEnabled
+  bool EnablePrivateImports = false;
+
   /// Enables the "fully resilient" resilience strategy.
   ///
   /// \see ResilienceStrategy::Resilient

include/swift/Option/Options.td

@@ -791,6 +791,10 @@ def enable_testing : Flag<["-"], "enable-testing">,
   Flags<[FrontendOption, NoInteractiveOption, HelpHidden]>,
   HelpText<"Allows this module's internal API to be accessed for testing">;
 
+def enable_private_imports : Flag<["-"], "enable-private-imports">,
+  Flags<[FrontendOption, NoInteractiveOption, HelpHidden]>,
+  HelpText<"Allows this module's internal and private API to be accessed">;
+
 def sanitize_EQ : CommaJoined<["-"], "sanitize=">,
   Flags<[FrontendOption, NoInteractiveOption]>, MetaVarName<"<check>">,
   HelpText<"Turn on runtime checks for erroneous behavior.">;

include/swift/Serialization/DeclTypeRecordNodes.def

@@ -168,6 +168,7 @@ OTHER(SUBSTITUTION_MAP, 236)
 
 OTHER(LOCAL_DISCRIMINATOR, 237)
 OTHER(PRIVATE_DISCRIMINATOR, 238)
+OTHER(FILENAME_FOR_PRIVATE, 239)
 
 OTHER(ABSTRACT_PROTOCOL_CONFORMANCE, 240)
 OTHER(NORMAL_PROTOCOL_CONFORMANCE, 241)

include/swift/Serialization/ModuleFormat.h

@@ -52,7 +52,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 462; // Last change: Add dynamicReplacement(for:)
+const uint16_t SWIFTMODULE_VERSION_MINOR = 463; // Last change: enable-private-imports
 
 using DeclIDField = BCFixed<31>;
 
@@ -592,7 +592,8 @@ namespace options_block {
     XCC,
     IS_SIB,
     IS_TESTABLE,
-    RESILIENCE_STRATEGY
+    RESILIENCE_STRATEGY,
+    ARE_PRIVATE_IMPORTS_ENABLED
   };
 
   using SDKPathLayout = BCRecordLayout<
@@ -614,6 +615,10 @@ namespace options_block {
     IS_TESTABLE
   >;
 
+  using ArePrivateImportsEnabledLayout = BCRecordLayout<
+    ARE_PRIVATE_IMPORTS_ENABLED
+  >;
+
   using ResilienceStrategyLayout = BCRecordLayout<
     RESILIENCE_STRATEGY,
     BCFixed<2>
@@ -1309,6 +1314,11 @@ namespace decls_block {
     BCVBR<2> // context-scoped discriminator counter
   >;
 
+  using FilenameForPrivateLayout = BCRecordLayout<
+    FILENAME_FOR_PRIVATE,
+    IdentifierIDField  // the file name, as an identifier
+  >;
+
   /// A placeholder for lack of concrete conformance information.
   using AbstractProtocolConformanceLayout = BCRecordLayout<
     ABSTRACT_PROTOCOL_CONFORMANCE,
@@ -1513,6 +1523,7 @@ namespace decls_block {
     = BCRecordLayout<RestatedObjCConformance_DECL_ATTR>;
   using ClangImporterSynthesizedTypeDeclAttrLayout
     = BCRecordLayout<ClangImporterSynthesizedType_DECL_ATTR>;
+  using PrivateImportDeclAttrLayout = BCRecordLayout<PrivateImport_DECL_ATTR>;
 
   using InlineDeclAttrLayout = BCRecordLayout<
     Inline_DECL_ATTR,

include/swift/Serialization/Validation.h

@@ -93,6 +93,7 @@ class ExtendedValidationInfo {
   SmallVector<StringRef, 4> ExtraClangImporterOpts;
   StringRef SDKPath;
   struct {
+    unsigned ArePrivateImportsEnabled : 1;
     unsigned IsSIB : 1;
     unsigned IsTestable : 1;
     unsigned ResilienceStrategy : 2;
@@ -117,6 +118,10 @@ class ExtendedValidationInfo {
   void setIsSIB(bool val) {
       Bits.IsSIB = val;
   }
+  bool arePrivateImportsEnabled() { return Bits.ArePrivateImportsEnabled; }
+  void setPrivateImportsEnabled(bool enabled) {
+    Bits.ArePrivateImportsEnabled = enabled;
+  }
   bool isTestable() const { return Bits.IsTestable; }
   void setIsTestable(bool val) {
     Bits.IsTestable = val;

lib/AST/Attr.cpp

@@ -468,6 +468,12 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
     }
     break;
   }
+
+  case DAK_PrivateImport: {
+    Printer.printAttrName("@_private(sourceFile: \"");
+    Printer << cast<PrivateImportAttr>(this)->getSourceFile() << "\")";
+    break;
+  }
 
   case DAK_SwiftNativeObjCRuntimeBase: {
     auto *attr = cast<SwiftNativeObjCRuntimeBaseAttr>(this);
@@ -621,6 +627,8 @@ StringRef DeclAttribute::getAttrName() const {
     return "objc";
   case DAK_DynamicReplacement:
     return "_dynamicReplacement";
+  case DAK_PrivateImport:
+    return "_private";
   case DAK_RestatedObjCConformance:
     return "_restatedObjCConformance";
   case DAK_Inline: {
@@ -785,6 +793,22 @@ ObjCAttr *ObjCAttr::clone(ASTContext &context) const {
   return attr;
 }
 
+PrivateImportAttr::PrivateImportAttr(SourceLoc atLoc, SourceRange baseRange,
+                                     StringRef sourceFile,
+                                     SourceRange parenRange)
+    : DeclAttribute(DAK_PrivateImport, atLoc, baseRange, /*Implicit=*/false),
+      SourceFile(sourceFile) {}
+
+PrivateImportAttr *PrivateImportAttr::create(ASTContext &Ctxt, SourceLoc AtLoc,
+                                             SourceLoc PrivateLoc,
+                                             SourceLoc LParenLoc,
+                                             StringRef sourceFile,
+                                             SourceLoc RParenLoc) {
+  return new (Ctxt)
+      PrivateImportAttr(AtLoc, SourceRange(PrivateLoc, LParenLoc), sourceFile,
+                        SourceRange(LParenLoc, RParenLoc));
+}
+
 DynamicReplacementAttr::DynamicReplacementAttr(SourceLoc atLoc,
                                                SourceRange baseRange,
                                                DeclName name,