AST: Promote AsyncSequenceFailure feature to the baseline.

include/swift/AST/PrintOptions.h

@@ -372,10 +372,6 @@ struct PrintOptions {
   /// Whether to suppress printing of custom attributes that are expanded macros.
   bool SuppressExpandedMacros = true;
 
-  /// Whether we're supposed to slap a @rethrows on `AsyncSequence` /
-  /// `AsyncIteratorProtocol` for backward-compatibility reasons.
-  bool AsyncSequenceRethrows = false;
-
   /// Suppress the @isolated(any) attribute.
   bool SuppressIsolatedAny = false;
 

include/swift/Basic/Features.def

@@ -170,7 +170,7 @@ SUPPRESSIBLE_LANGUAGE_FEATURE(PrimaryAssociatedTypes2, 346, "Primary associated
 BASELINE_LANGUAGE_FEATURE(UnavailableFromAsync, 0, "@_unavailableFromAsync")
 BASELINE_LANGUAGE_FEATURE(NoAsyncAvailability, 340, "@available(*, noasync)")
 BASELINE_LANGUAGE_FEATURE(AssociatedTypeAvailability, 0, "Availability on associated types")
-SUPPRESSIBLE_LANGUAGE_FEATURE(AsyncSequenceFailure, 0, "Failure associated type on AsyncSequence and AsyncIteratorProtocol")
+BASELINE_LANGUAGE_FEATURE(AsyncSequenceFailure, 0, "Failure associated type on AsyncSequence and AsyncIteratorProtocol")
 BASELINE_LANGUAGE_FEATURE(BuiltinIntLiteralAccessors, 368, "Builtin.IntLiteral accessors")
 LANGUAGE_FEATURE(Macros, 0, "Macros")
 LANGUAGE_FEATURE(FreestandingExpressionMacros, 382, "Expression macros")

lib/AST/ASTPrinter.cpp

@@ -1208,11 +1208,6 @@ static bool hasLessAccessibleSetter(const AbstractStorageDecl *ASD) {
   return ASD->getSetterFormalAccess() < ASD->getFormalAccess();
 }
 
-static bool isImplicitRethrowsProtocol(const ProtocolDecl *proto) {
-  return proto->isSpecificProtocol(KnownProtocolKind::AsyncSequence) ||
-      proto->isSpecificProtocol(KnownProtocolKind::AsyncIteratorProtocol);
-}
-
 void PrintAST::printAttributes(const Decl *D) {
   if (Options.SkipAttributes)
     return;
@@ -1223,17 +1218,6 @@ void PrintAST::printAttributes(const Decl *D) {
 
   auto attrs = D->getAttrs();
 
-  // When printing a Swift interface, make sure that older compilers see
-  // @rethrows on the AsyncSequence and AsyncIteratorProtocol.
-  if (Options.AsyncSequenceRethrows && Options.IsForSwiftInterface) {
-    if (auto proto = dyn_cast<ProtocolDecl>(D)) {
-      if (isImplicitRethrowsProtocol(proto)) {
-        Printer << "@rethrows";
-        Printer.printNewline();
-      }
-    }
-  }
-
   // Save the current number of exclude attrs to restore once we're done.
   unsigned originalExcludeAttrCount = Options.ExcludeAttrList.size();
 
@@ -3067,12 +3051,6 @@ static void suppressingFeaturePrimaryAssociatedTypes2(PrintOptions &options,
   options.PrintPrimaryAssociatedTypes = originalPrintPrimaryAssociatedTypes;
 }
 
-static void
-suppressingFeatureAsyncSequenceFailure(
-    PrintOptions &options, llvm::function_ref<void()> action) {
-  llvm::SaveAndRestore<bool> saved(options.AsyncSequenceRethrows, true);
-  action();
-}
 static void
 suppressingFeatureLexicalLifetimes(PrintOptions &options,
                                    llvm::function_ref<void()> action) {

lib/AST/FeatureSet.cpp

@@ -150,19 +150,6 @@ static bool usesFeaturePrimaryAssociatedTypes2(Decl *decl) {
   return false;
 }
 
-static bool isImplicitRethrowsProtocol(const ProtocolDecl *proto) {
-  return proto->isSpecificProtocol(KnownProtocolKind::AsyncSequence) ||
-         proto->isSpecificProtocol(KnownProtocolKind::AsyncIteratorProtocol);
-}
-
-static bool usesFeatureAsyncSequenceFailure(Decl *decl) {
-  if (auto proto = dyn_cast<ProtocolDecl>(decl)) {
-    return isImplicitRethrowsProtocol(proto);
-  }
-
-  return false;
-}
-
 static bool usesFeatureMacros(Decl *decl) { return isa<MacroDecl>(decl); }
 
 static bool usesFeatureFreestandingExpressionMacros(Decl *decl) {

test/ModuleInterface/async_sequence_rethrows.swift

@@ -4,7 +4,7 @@
 
 // REQUIRES: concurrency
 
-// CHECK: @rethrows
-// CHECK-NEXT: public protocol AsyncIteratorProtocol
+// CHECK-NOT: @rethrows
+// CHECK: public protocol AsyncIteratorProtocol
 public protocol AsyncIteratorProtocol {
 }