[ClangImporter] Remove support for Swift 3 mode (#17722)

Not as exciting as some of the other components, but still!

Author: jrose-apple

lib/ClangImporter/ImportDecl.cpp

@@ -1962,7 +1962,7 @@ shouldSuppressGenericParamsImport(const LangOptions &langOpts,
     return module->getTopLevelModuleName() == "Foundation";
   };
 
-  if (langOpts.isSwiftVersion3() || isFromFoundationModule(decl)) {
+  if (isFromFoundationModule(decl)) {
     // In Swift 3 we used a hardcoded list of declarations, and made all of
     // their subclasses drop their generic parameters when imported.
     while (decl) {
@@ -7558,41 +7558,6 @@ void ClangImporter::Implementation::importAttributes(
                                           PlatformAgnostic, /*Implicit=*/false);
 
       MappedDecl->getAttrs().add(AvAttr);
-
-      // For enum cases introduced in the 2017 SDKs, add
-      // @_downgrade_exhaustivity_check in Swift 3.
-      if (C.LangOpts.isSwiftVersion3() && isa<EnumElementDecl>(MappedDecl)) {
-        bool downgradeExhaustivity = false;
-        switch (*platformK) {
-        case PlatformKind::OSX:
-        case PlatformKind::OSXApplicationExtension:
-          downgradeExhaustivity = (introduced.getMajor() == 10 &&
-                                   introduced.getMinor() &&
-                                   *introduced.getMinor() == 13);
-          break;
-
-        case PlatformKind::iOS:
-        case PlatformKind::iOSApplicationExtension:
-        case PlatformKind::tvOS:
-        case PlatformKind::tvOSApplicationExtension:
-          downgradeExhaustivity = (introduced.getMajor() == 11);
-          break;
-
-        case PlatformKind::watchOS:
-        case PlatformKind::watchOSApplicationExtension:
-          downgradeExhaustivity = (introduced.getMajor() == 4);
-          break;
-
-        case PlatformKind::none:
-          break;
-        }
-
-        if (downgradeExhaustivity) {
-          auto attr =
-            new (C) DowngradeExhaustivityCheckAttr(/*isImplicit=*/true);
-          MappedDecl->getAttrs().add(attr);
-        }
-      }
     }
   }
 
@@ -7723,8 +7688,7 @@ ClangImporter::Implementation::importDeclImpl(const clang::NamedDecl *ClangDecl,
       }
     }
     if (auto method = dyn_cast<clang::ObjCMethodDecl>(ClangDecl)) {
-      if (!SwiftContext.LangOpts.isSwiftVersion3() &&
-          method->isDesignatedInitializerForTheInterface()) {
+      if (method->isDesignatedInitializerForTheInterface()) {
         const clang::ObjCInterfaceDecl *theClass = method->getClassInterface();
         assert(theClass && "cannot be a protocol method here");
         // Only allow this to affect declarations in the same top-level module

lib/ClangImporter/ImportType.cpp

@@ -884,10 +884,7 @@ namespace {
               }
               importedTypeArg = subresult.AbstractType;
             } else if (typeParam->getSuperclass() &&
-                       (Impl.SwiftContext.isSwiftVersion3() ||
-                        typeParam->getConformingProtocols().empty())) {
-              // In Swift 3 mode, discard the protocol bounds if there is
-              // a superclass bound.
+                       typeParam->getConformingProtocols().empty()) {
               importedTypeArg = typeParam->getSuperclass();
             } else {
               SmallVector<Type, 4> memberTypes;
@@ -1039,10 +1036,7 @@ namespace {
         }
       }
 
-      // Swift 3 compatibility -- don't import subclass existentials
-      if (!type->qual_empty() &&
-          (importedType->isAnyObject() ||
-           !Impl.SwiftContext.isSwiftVersion3())) {
+      if (!type->qual_empty()) {
         SmallVector<Type, 4> members;
         if (!importedType->isAnyObject())
           members.push_back(importedType);
@@ -1555,23 +1549,7 @@ ImportedType ClangImporter::Implementation::importFunctionReturnType(
     bool allowNSUIntegerAsInt) {
 
   // Hardcode handling of certain result types for builtins.
-  auto builtinID = clangDecl->getBuiltinID();
-  switch (builtinID) {
-  case clang::Builtin::NotBuiltin:
-    break;
-  case clang::Builtin::BIstrxfrm:
-  case clang::Builtin::BIstrcspn:
-  case clang::Builtin::BIstrspn:
-  case clang::Builtin::BIstrlen:
-  case clang::Builtin::BIstrlcpy:
-  case clang::Builtin::BIstrlcat:
-    // This is a list of all built-ins with a result type of 'size_t' that
-    // existed in Swift 3. We didn't have special handling for builtins at
-    // that time, and so these had a result type of UInt.
-    if (SwiftContext.isSwiftVersion3())
-      break;
-    LLVM_FALLTHROUGH;
-  default:
+  if (auto builtinID = clangDecl->getBuiltinID()) {
     switch (getClangASTContext().BuiltinInfo.getTypeString(builtinID)[0]) {
     case 'z': // size_t
     case 'Y': // ptrdiff_t

test/ClangImporter/availability_open_enums.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -verify -I %S/Inputs/custom-modules -swift-version 4 -enable-nonfrozen-enum-exhaustivity-diagnostics %s
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -verify -I %S/Inputs/custom-modules -enable-nonfrozen-enum-exhaustivity-diagnostics %s
 
 // REQUIRES: objc_interop
 

test/ClangImporter/clang_builtins.swift

@@ -1,4 +1,4 @@
-// RUN: not %target-swift-frontend -swift-version 4 -typecheck %s 2>&1 | %FileCheck -check-prefix=CHECK -check-prefix=CHECK-%target-runtime %s
+// RUN: not %target-swift-frontend -typecheck %s 2>&1 | %FileCheck -check-prefix=CHECK -check-prefix=CHECK-%target-runtime %s
 
 #if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
   import Darwin

test/ClangImporter/subclass_existentials.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -verify -o - -primary-file %s -swift-version 4 -I %S/Inputs/custom-modules/
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -verify -o - -primary-file %s -I %S/Inputs/custom-modules/
 
 // REQUIRES: objc_interop