Remove Swift 3 default argument behavior

Author: slavapestov

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/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;