Revert "[Mangling] Uniformly use "So" for imported decls."

This reverts commit 25985cb. For now,
we're trying to avoid spurious non-structural changes to the mangling,
so that the /old/ mangling doesn't appear to change. That doesn't mean
no changes at all, but we can save this one for later.

Author: jrose-apple

include/swift/Strings.h

@@ -39,9 +39,9 @@ namespace swift {
   static const char LLDB_EXPRESSIONS_MODULE_NAME_PREFIX[] = "__lldb_expr_";
 
   /// The name of the fake module used to hold imported Objective-C things.
-  static const char MANGLING_MODULE_OBJC[] = "__C";
-  /// The name of the fake module used to hold synthesized ClangImporter things.
-  static const char MANGLING_MODULE_CLANG_IMPORTER[] = "__C_Synthesized";
+  static const char MANGLING_MODULE_OBJC[] = "__ObjC";
+  /// The name of the fake module used to hold imported C things.
+  static const char MANGLING_MODULE_C[] = "__C";
 } // end namespace swift
 
 #endif // SWIFT_STRINGS_H

lib/AST/ASTMangler.cpp

@@ -1073,21 +1073,28 @@ void ASTMangler::appendImplFunctionType(SILFunctionType *fn) {
 /// Mangle the context of the given declaration as a <context.
 /// This is the top-level entrypoint for mangling <context>.
 void ASTMangler::appendContextOf(const ValueDecl *decl) {
-  // Declarations provided by a C module have a special context
+  auto clangDecl = decl->getClangDecl();
+
+  // Classes and protocols implemented in Objective-C have a special context
   // mangling.
   //   known-context ::= 'So'
-  //
-  // Also handle top-level imported declarations that don't have corresponding
-  // Clang decls. Check getKind() directly to avoid a layering dependency.
+  if (isa<ClassDecl>(decl) && clangDecl) {
+    assert(isa<clang::ObjCInterfaceDecl>(clangDecl) ||
+           isa<clang::TypedefDecl>(clangDecl));
+    return appendOperator("So");
+  }
+
+  if (isa<ProtocolDecl>(decl) && clangDecl) {
+    assert(isa<clang::ObjCProtocolDecl>(clangDecl));
+    return appendOperator("So");
+  }
+
+  // Declarations provided by a C module have a special context mangling.
   //   known-context ::= 'SC'
+  // Do a dance to avoid a layering dependency.
   if (auto file = dyn_cast<FileUnit>(decl->getDeclContext())) {
-    if (file->getKind() == FileUnitKind::ClangModule) {
-      // FIXME: Import-as-member Clang decls should appear under 'So' as well,
-      // rather than under their current parent.
-      if (decl->getClangDecl())
-        return appendOperator("So");
+    if (file->getKind() == FileUnitKind::ClangModule)
       return appendOperator("SC");
-    }
   }
 
   // Just mangle the decl's DC.
@@ -1285,7 +1292,7 @@ void ASTMangler::appendModule(const ModuleDecl *module) {
   StringRef ModName = module->getName().str();
   if (ModName == MANGLING_MODULE_OBJC)
     return appendOperator("So");
-  if (ModName == MANGLING_MODULE_CLANG_IMPORTER)
+  if (ModName == MANGLING_MODULE_C)
     return appendOperator("SC");
 
   appendIdentifier(ModName);

lib/Demangling/Demangler.cpp

@@ -505,7 +505,7 @@ NodePointer Demangler::demangleStandardSubstitution() {
     case 'o':
       return createNode(Node::Kind::Module, MANGLING_MODULE_OBJC);
     case 'C':
-      return createNode(Node::Kind::Module, MANGLING_MODULE_CLANG_IMPORTER);
+      return createNode(Node::Kind::Module, MANGLING_MODULE_C);
     case 'g': {
       NodePointer OptionalTy =
         createType(createWithChildren(Node::Kind::BoundGenericEnum,

lib/Demangling/OldDemangler.cpp

@@ -863,8 +863,7 @@ class OldDemangler {
     if (Mangled.nextIf('o'))
       return Factory.createNode(Node::Kind::Module, MANGLING_MODULE_OBJC);
     if (Mangled.nextIf('C'))
-      return Factory.createNode(Node::Kind::Module,
-                                MANGLING_MODULE_CLANG_IMPORTER);
+      return Factory.createNode(Node::Kind::Module, MANGLING_MODULE_C);
     if (Mangled.nextIf('a'))
       return createSwiftType(Node::Kind::Structure, "Array");
     if (Mangled.nextIf('b'))

lib/Demangling/OldRemangler.cpp

@@ -357,7 +357,7 @@ bool Remangler::mangleStandardSubstitution(Node *node) {
     case Node::Kind::Module:
       SUCCESS_IF_TEXT_IS(STDLIB_NAME, "s");
       SUCCESS_IF_TEXT_IS(MANGLING_MODULE_OBJC, "So");
-      SUCCESS_IF_TEXT_IS(MANGLING_MODULE_CLANG_IMPORTER, "SC");
+      SUCCESS_IF_TEXT_IS(MANGLING_MODULE_C, "SC");
       break;
     case Node::Kind::Structure:
       if (isInSwiftModule(node)) {

lib/Demangling/Remangler.cpp

@@ -1292,7 +1292,7 @@ void Remangler::mangleModule(Node *node) {
     Buffer << 's';
   } else if (node->getText() == MANGLING_MODULE_OBJC) {
     Buffer << "So";
-  } else if (node->getText() == MANGLING_MODULE_CLANG_IMPORTER) {
+  } else if (node->getText() == MANGLING_MODULE_C) {
     Buffer << "SC";
   } else {
     mangleIdentifier(node);

lib/IDE/TypeReconstruction.cpp

@@ -101,7 +101,7 @@ class DeclsLookupSource {
     assert(!module_name.empty());
     static ConstString g_ObjectiveCModule(MANGLING_MODULE_OBJC);
     static ConstString g_BuiltinModule("Builtin");
-    static ConstString g_CModule(MANGLING_MODULE_CLANG_IMPORTER);
+    static ConstString g_CModule(MANGLING_MODULE_C);
     if (allow_crawler) {
       if (module_name == g_ObjectiveCModule || module_name == g_CModule)
         return DeclsLookupSource(&ast, module_name);

lib/RemoteAST/RemoteAST.cpp

@@ -16,7 +16,6 @@
 
 #include "swift/RemoteAST/RemoteAST.h"
 #include "swift/Remote/MetadataReader.h"
-#include "swift/Strings.h"
 #include "swift/Subsystems.h"
 #include "swift/AST/ASTContext.h"
 #include "swift/AST/Decl.h"
@@ -523,8 +522,7 @@ bool RemoteASTTypeBuilder::isForeignModule(const Demangle::NodePointer &node) {
   if (node->getKind() != Demangle::Node::Kind::Module)
     return false;
 
-  return (node->getText() == MANGLING_MODULE_OBJC ||
-          node->getText() == MANGLING_MODULE_CLANG_IMPORTER);
+  return (node->getText() == "__ObjC");
 }
 
 DeclContext *

stdlib/public/runtime/Demangle.cpp

@@ -131,7 +131,9 @@ swift::_swift_buildDemanglingForMetadata(const Metadata *type,
     auto objcWrapper = static_cast<const ObjCClassWrapperMetadata *>(type);
     const char *className = class_getName((Class)objcWrapper->Class);
 
-    auto module = Dem.createNode(Node::Kind::Module, MANGLING_MODULE_OBJC);
+    // ObjC classes mangle as being in the magic "__ObjC" module.
+    auto module = Dem.createNode(Node::Kind::Module, "__ObjC");
+    
     auto node = Dem.createNode(Node::Kind::Class);
     node->addChild(module, Dem);
     node->addChild(Dem.createNode(Node::Kind::Identifier,

test/APINotes/versioned.swift

@@ -88,12 +88,12 @@ func testAKA(structValue: ImportantCStruct, aliasValue: ImportantCAlias) {
 
 #if !swift(>=4)
 func useSwift3Name(_: ImportantCStruct) {}
-// CHECK-SILGEN-3: sil hidden @_T09versioned13useSwift3NameySo20VeryImportantCStructVF
+// CHECK-SILGEN-3: sil hidden @_T09versioned13useSwift3NameySC20VeryImportantCStructVF
 
 func useNewlyNested(_: InnerInSwift4) {}
-// CHECK-SILGEN-3: sil hidden @_T09versioned14useNewlyNestedySo5OuterV5InnerVF
+// CHECK-SILGEN-3: sil hidden @_T09versioned14useNewlyNestedySC5OuterV5InnerVF
 #endif
 
 func useSwift4Name(_: VeryImportantCStruct) {}
-// CHECK-SILGEN: sil hidden @_T09versioned13useSwift4NameySo20VeryImportantCStructVF
+// CHECK-SILGEN: sil hidden @_T09versioned13useSwift4NameySC20VeryImportantCStructVF
 

test/ClangImporter/ctypes_ir.swift

@@ -27,7 +27,7 @@ func testStructWithFlexibleArray(_ s : StructWithFlexibleArray) {
 }
 
 // Make sure flexible array struct member isn't represented in IR function signature as i0 (or at all). rdar://problem/18510461
-// CHECK-LABEL: define hidden swiftcc void @_T09ctypes_ir27testStructWithFlexibleArrayySo0defG0VF(i32)
+// CHECK-LABEL: define hidden swiftcc void @_T09ctypes_ir27testStructWithFlexibleArrayySC0defG0VF(i32)
 
 typealias EightUp = (Int8, Int8, Int8, Int8, Int8, Int8, Int8, Int8)
 

test/Demangle/Inputs/manglings.txt

@@ -25,7 +25,7 @@ _TtGSqSS_ ---> Swift.String?
 _TtGSQSS_ ---> Swift.String!
 _TtGVs10DictionarySSSi_ ---> [Swift.String : Swift.Int]
 _TtVs7CString ---> Swift.CString
-_TtCSo8NSObject ---> __C.NSObject
+_TtCSo8NSObject ---> __ObjC.NSObject
 _TtO6Monads6Either ---> Monads.Either
 _TtbSiSu ---> @convention(block) (Swift.Int) -> Swift.UInt
 _TtcSiSu ---> @convention(c) (Swift.Int) -> Swift.UInt
@@ -78,11 +78,11 @@ _TF3foog3barSi ---> foo.bar.getter : Swift.Int
 _TF3foos3barSi ---> foo.bar.setter : Swift.Int
 _TFC3foo3bar3basfT3zimCS_3zim_T_ ---> foo.bar.bas(zim: foo.zim) -> ()
 _TToFC3foo3bar3basfT3zimCS_3zim_T_ ---> {T:_TFC3foo3bar3basfT3zimCS_3zim_T_,C} @objc foo.bar.bas(zim: foo.zim) -> ()
-_TTOFSC3fooFTSdSd_Sd ---> {T:_TFSC3fooFTSdSd_Sd} @nonobjc __C_Synthesized.foo(Swift.Double, Swift.Double) -> Swift.Double
+_TTOFSC3fooFTSdSd_Sd ---> {T:_TFSC3fooFTSdSd_Sd} @nonobjc __C.foo(Swift.Double, Swift.Double) -> Swift.Double
 _T03foo3barC3basyAA3zimCAE_tFTo ---> {T:_T03foo3barC3basyAA3zimCAE_tF,C} @objc foo.bar.bas(zim: foo.zim) -> ()
-_T0SC3fooS2d_SdtFTO ---> {T:_T0SC3fooS2d_SdtF} @nonobjc __C_Synthesized.foo(Swift.Double, Swift.Double) -> Swift.Double
+_T0SC3fooS2d_SdtFTO ---> {T:_T0SC3fooS2d_SdtF} @nonobjc __C.foo(Swift.Double, Swift.Double) -> Swift.Double
 _S3foo3barC3basyAA3zimCAE_tFTo ---> {T:_S3foo3barC3basyAA3zimCAE_tF,C} @objc foo.bar.bas(zim: foo.zim) -> ()
-_SSC3fooS2d_SdtFTO ---> {T:_SSC3fooS2d_SdtF} @nonobjc __C_Synthesized.foo(Swift.Double, Swift.Double) -> Swift.Double
+_SSC3fooS2d_SdtFTO ---> {T:_SSC3fooS2d_SdtF} @nonobjc __C.foo(Swift.Double, Swift.Double) -> Swift.Double
 _TTDFC3foo3bar3basfT3zimCS_3zim_T_ ---> dynamic foo.bar.bas(zim: foo.zim) -> ()
 _TFC3foo3bar3basfT3zimCS_3zim_T_ ---> foo.bar.bas(zim: foo.zim) -> ()
 _TF3foooi1pFTCS_3barVS_3bas_OS_3zim ---> foo.+ infix(foo.bar, foo.bas) -> foo.zim
@@ -120,7 +120,7 @@ _TWGC3foo3barS_8barrableS_ ---> generic protocol witness table for foo.bar : foo
 _TWIC3foo3barS_8barrableS_ ---> {C} instantiation function for generic protocol witness table for foo.bar : foo.barrable in foo
 _TWtC3foo3barS_8barrableS_4fred ---> {C} associated type metadata accessor for fred in foo.bar : foo.barrable in foo
 _TWTC3foo3barS_8barrableS_4fredS_6thomas ---> {C} associated type witness table accessor for fred : foo.thomas in foo.bar : foo.barrable in foo
-_TFSCg5greenVSC5Color ---> __C_Synthesized.green.getter : __C_Synthesized.Color
+_TFSCg5greenVSC5Color ---> __C.green.getter : __C.Color
 _TIF1t1fFT1iSi1sSS_T_A_ ---> default argument 0 of t.f(i: Swift.Int, s: Swift.String) -> ()
 _TIF1t1fFT1iSi1sSS_T_A0_ ---> default argument 1 of t.f(i: Swift.Int, s: Swift.String) -> ()
 _TFSqcfT_GSqx_ ---> Swift.Optional.init() -> A?
@@ -169,8 +169,8 @@ _TFCF5types1gFT1bSb_T_L0_10Collection3zimfT_T_ ---> zim() -> () in Collection #2
 _TFF17capture_promotion22test_capture_promotionFT_FT_SiU_FT_Si_promote0 ---> closure #1 () -> Swift.Int in capture_promotion.test_capture_promotion() -> () -> Swift.Int with unmangled suffix "_promote0"
 _TFIVs8_Processi10_argumentsGSaSS_U_FT_GSaSS_ ---> _arguments : [Swift.String] in variable initialization expression of Swift._Process with unmangled suffix "U_FT_GSaSS_"
 _TFIvVs8_Process10_argumentsGSaSS_iU_FT_GSaSS_ ---> closure #1 () -> [Swift.String] in variable initialization expression of Swift._Process._arguments : [Swift.String]
-_TFCSo1AE ---> __C.A.__ivar_destroyer
-_TFCSo1Ae ---> __C.A.__ivar_initializer
+_TFCSo1AE ---> __ObjC.A.__ivar_destroyer
+_TFCSo1Ae ---> __ObjC.A.__ivar_initializer
 _TTWC13call_protocol1CS_1PS_FS1_3foofT_Si ---> protocol witness for call_protocol.P.foo() -> Swift.Int in conformance call_protocol.C : call_protocol.P in call_protocol
 _T013call_protocol1CCAA1PA2aDP3fooSiyFTW ---> {T:} protocol witness for call_protocol.P.foo() -> Swift.Int in conformance call_protocol.C : call_protocol.P in call_protocol
 _TFC12dynamic_self1X1ffT_DS0_ ---> dynamic_self.X.f() -> Self
@@ -249,7 +249,7 @@ _T0s10DictionaryV3t17E6Index2V1loiSbAEyxq__G_AGtFZ ---> static (extension in t17
 _T08mangling14varargsVsArrayySaySiG3arrd_SS1ntF ---> mangling.varargsVsArray(arr: Swift.Int..., n: Swift.String) -> ()
 _T08mangling14varargsVsArrayySaySiG3arrd_tF ---> mangling.varargsVsArray(arr: Swift.Int...) -> ()
 _T0s13_UnicodeViewsVss22RandomAccessCollectionRzs0A8EncodingR_11SubSequence_5IndexQZAFRtzsAcERpzAE_AEQZAIRSs15UnsignedInteger8Iterator_7ElementRPzAE_AlMQZANRS13EncodedScalar_AlMQY_AORSr0_lE13CharacterViewVyxq__G ---> (extension in Swift):Swift._UnicodeViews<A, B><A, B where A: Swift.RandomAccessCollection, B: Swift.UnicodeEncoding, A.Index == A.SubSequence.Index, A.SubSequence: Swift.RandomAccessCollection, A.SubSequence == A.SubSequence.SubSequence, A.Iterator.Element: Swift.UnsignedInteger, A.Iterator.Element == A.SubSequence.Iterator.Element, A.SubSequence.Iterator.Element == B.EncodedScalar.Iterator.Element>.CharacterView
-_T010Foundation11MeasurementV12SimulatorKitSo9UnitAngleCRszlE11OrientationO2eeoiSbAcDEAGOyAF_G_AKtFZ ---> static (extension in SimulatorKit):Foundation.Measurement<A where A == __C.UnitAngle>.Orientation.== infix((extension in SimulatorKit):Foundation.Measurement<__C.UnitAngle>.Orientation, (extension in SimulatorKit):Foundation.Measurement<__C.UnitAngle>.Orientation) -> Swift.Bool
+_T010Foundation11MeasurementV12SimulatorKitSo9UnitAngleCRszlE11OrientationO2eeoiSbAcDEAGOyAF_G_AKtFZ ---> static (extension in SimulatorKit):Foundation.Measurement<A where A == __ObjC.UnitAngle>.Orientation.== infix((extension in SimulatorKit):Foundation.Measurement<__ObjC.UnitAngle>.Orientation, (extension in SimulatorKit):Foundation.Measurement<__ObjC.UnitAngle>.Orientation) -> Swift.Bool
 _T04main1_yyF ---> main._() -> ()
 _T04test6testitSiyt_tF ---> test.testit(()) -> Swift.Int