Remove remaining isSwiftVersion3() checks

include/swift/AST/ASTContext.h

@@ -924,9 +924,6 @@ class ASTContext final {
   CanGenericSignature getExistentialSignature(CanType existential,
                                               ModuleDecl *mod);
 
-  /// Whether our effective Swift version is in the Swift 3 family.
-  bool isSwiftVersion3() const { return LangOpts.isSwiftVersion3(); }
-
   /// Whether our effective Swift version is at least 'major'.
   ///
   /// This is usually the check you want; for example, when introducing

include/swift/AST/DiagnosticsSema.def

@@ -1865,9 +1865,6 @@ NOTE(declared_protocol_conformance_here,none,
      "%0 implicitly conforms to protocol %2}1 here",
      (Type, unsigned, DeclName, DeclName))
 
-WARNING(witness_unavailable_warn,none,
-        "unavailable %0 %1 was used to satisfy a requirement of protocol %2",
-        (DescriptiveDeclKind, DeclName, DeclName))
 ERROR(witness_unavailable,none,
         "unavailable %0 %1 was used to satisfy a requirement of protocol %2",
         (DescriptiveDeclKind, DeclName, DeclName))

include/swift/Basic/LangOptions.h

@@ -358,11 +358,6 @@ namespace swift {
       return CustomConditionalCompilationFlags;
     }
 
-    /// Whether our effective Swift version is in the Swift 3 family
-    bool isSwiftVersion3() const {
-      return EffectiveLanguageVersion.isVersion3();
-    }
-
     /// Whether our effective Swift version is at least 'major'.
     ///
     /// This is usually the check you want; for example, when introducing

include/swift/Basic/Version.h

@@ -107,9 +107,6 @@ class Version {
   /// compiler to act as if it is version 3.1.
   Optional<Version> getEffectiveLanguageVersion() const;
 
-  /// Whether this version is in the Swift 3 family
-  bool isVersion3() const { return !empty() && Components[0] == 3; }
-
   /// Whether this version is greater than or equal to the given major version
   /// number.
   bool isVersionAtLeast(unsigned major, unsigned minor = 0) const {

lib/ClangImporter/ClangAdapter.cpp

@@ -741,11 +741,10 @@ OptionalTypeKind importer::getParamOptionality(version::Version swiftVersion,
     return OTK_None;
 
   // Check for the 'static' annotation on C arrays.
-  if (!swiftVersion.isVersion3())
-    if (const auto *DT = dyn_cast<clang::DecayedType>(paramTy))
-      if (const auto *AT = DT->getOriginalType()->getAsArrayTypeUnsafe())
-        if (AT->getSizeModifier() == clang::ArrayType::Static)
-          return OTK_None;
+  if (const auto *DT = dyn_cast<clang::DecayedType>(paramTy))
+    if (const auto *AT = DT->getOriginalType()->getAsArrayTypeUnsafe())
+      if (AT->getSizeModifier() == clang::ArrayType::Static)
+        return OTK_None;
 
   // Default to implicitly unwrapped optionals.
   return OTK_ImplicitlyUnwrappedOptional;

lib/Frontend/CompilerInvocation.cpp

@@ -364,8 +364,7 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   Opts.EnableSwift3ObjCInference =
     Args.hasFlag(OPT_enable_swift3_objc_inference,
-                 OPT_disable_swift3_objc_inference,
-                 Opts.isSwiftVersion3());
+                 OPT_disable_swift3_objc_inference, false);
 
   if (Opts.EnableSwift3ObjCInference) {
     if (const Arg *A = Args.getLastArg(

lib/Migrator/Migrator.cpp

@@ -132,23 +132,6 @@ Migrator::performAFixItMigration(version::Version SwiftLanguageVersion) {
     LLVMArgs.erase(aarch64_use_tbi);
   }
 
-  if (StartInvocation.getLangOptions().EffectiveLanguageVersion.isVersion3()) {
-    // SE-0160: When migrating, always use the Swift 3 @objc inference rules,
-    // which drives warnings with the "@objc" Fix-Its.
-    Invocation.getLangOptions().EnableSwift3ObjCInference = true;
-
-    // The default behavior of the migrator, referred to as "minimal" migration
-    // in SE-0160, only adds @objc Fix-Its to those cases where the Objective-C
-    // entry point is explicitly used somewhere in the source code. The user
-    // may also select a workflow that adds @objc for every declaration that
-    // would infer @objc under the Swift 3 rules but would no longer infer
-    // @objc in Swift 4.
-    Invocation.getLangOptions().WarnSwift3ObjCInference =
-      getMigratorOptions().KeepObjcVisibility
-        ? Swift3ObjCInferenceWarnings::Complete
-        : Swift3ObjCInferenceWarnings::Minimal;
-  }
-
   const auto &OrigFrontendOpts = StartInvocation.getFrontendOptions();
 
   assert(OrigFrontendOpts.InputsAndOutputs.hasPrimaryInputs() &&

lib/SIL/SILDeclRef.cpp

@@ -887,8 +887,8 @@ SubclassScope SILDeclRef::getSubclassScope() const {
   if (isThunk() || isForeign)
     return SubclassScope::NotApplicable;
 
-  // Default arg generators only need to be visible in Swift 3.
-  if (isDefaultArgGenerator() && !context->getASTContext().isSwiftVersion3())
+  // Default arg generators are not visible.
+  if (isDefaultArgGenerator())
     return SubclassScope::NotApplicable;
 
   auto *classType = context->getSelfClassDecl();

lib/SILGen/SILGenBridging.cpp

@@ -1425,14 +1425,10 @@ void SILGenFunction::emitNativeToForeignThunk(SILDeclRef thunk) {
     }
 
     if (auto attr = decl->getAttrs().getAttribute<ObjCAttr>()) {
-      // If @objc was inferred based on the Swift 3 @objc inference rules, but
-      // we aren't compiling in Swift 3 compatibility mode, emit a call to
-      // Builtin.swift3ImplicitObjCEntrypoint() to enable runtime logging of
-      // the uses of such entrypoints.
-      if (attr->isSwift3Inferred() &&
-          !decl->isDynamic() &&
-          !getASTContext().LangOpts.isSwiftVersion3()) {
-
+      // If @objc was inferred based on the Swift 3 @objc inference rules, emit
+      // a call to Builtin.swift3ImplicitObjCEntrypoint() to enable runtime
+      // logging of the uses of such entrypoints.
+      if (attr->isSwift3Inferred() && !decl->isDynamic()) {
         // Get the starting source location of the declaration so we can say
         // exactly where to stick '@objc'.
         SourceLoc objcInsertionLoc =

lib/Sema/TypeCheckProtocol.cpp

@@ -3084,16 +3084,14 @@ ConformanceChecker::resolveWitnessViaLookup(ValueDecl *requirement) {
 
       break;
 
-    case CheckKind::WitnessUnavailable: {
-      bool emitError = !witness->getASTContext().LangOpts.isSwiftVersion3();
-      diagnoseOrDefer(requirement, /*isError=*/emitError,
-        [witness, requirement, emitError](
+    case CheckKind::WitnessUnavailable:
+      diagnoseOrDefer(requirement, /*isError=*/true,
+        [witness, requirement](
                                     NormalProtocolConformance *conformance) {
           auto &diags = witness->getASTContext().Diags;
           SourceLoc diagLoc = getLocForDiagnosingWitness(conformance, witness);
           diags.diagnose(diagLoc,
-                         emitError ? diag::witness_unavailable
-                                   : diag::witness_unavailable_warn,
+                         diag::witness_unavailable,
                          witness->getDescriptiveKind(),
                          witness->getFullName(),
                          conformance->getProtocol()->getFullName());
@@ -3104,7 +3102,6 @@ ConformanceChecker::resolveWitnessViaLookup(ValueDecl *requirement) {
         });
       break;
     }
-    }
 
     if (auto *classDecl = Adoptee->getClassOrBoundGenericClass()) {
       if (!classDecl->isFinal()) {

lib/Sema/TypeCheckStmt.cpp

@@ -1495,7 +1495,7 @@ void TypeChecker::checkDefaultArguments(ParameterList *params,
   // caller.
   if (auto *func = dyn_cast<AbstractFunctionDecl>(VD)) {
     auto expansion = func->getResilienceExpansion();
-    if (!Context.isSwiftVersion3() && access.isPublic())
+    if (access.isPublic())
       expansion = ResilienceExpansion::Minimal;
 
     func->setDefaultArgumentResilienceExpansion(expansion);

lib/TBDGen/TBDGen.cpp

@@ -170,9 +170,7 @@ void TBDGenVisitor::visitAbstractFunctionDecl(AbstractFunctionDecl *AFD) {
     addSymbol(SILDeclRef(AFD).asForeign());
   }
 
-  auto publicDefaultArgGenerators =
-      SwiftModule->getASTContext().isSwiftVersion3() ||
-      SwiftModule->isTestingEnabled();
+  auto publicDefaultArgGenerators = SwiftModule->isTestingEnabled();
   if (!publicDefaultArgGenerators)
     return;