Print @_nonSendable extension in module interfaces

…instead of printing the attribute itself. This allows uses of @_nonSendable to back-deploy.

Author: beccadax

include/swift/AST/Decl.h

@@ -1284,6 +1284,8 @@ class ExtensionDecl final : public GenericContext, public Decl,
   SourceLoc getStartLoc() const { return ExtensionLoc; }
   SourceLoc getLocFromSource() const { return ExtensionLoc; }
   SourceRange getSourceRange() const {
+    if (!Braces.isValid())
+      return SourceRange(ExtensionLoc);
     return { ExtensionLoc, Braces.End };
   }
 

lib/AST/ASTPrinter.cpp

@@ -263,7 +263,8 @@ PrintOptions PrintOptions::printSwiftInterfaceFile(ModuleDecl *ModuleToPrint,
     DAK_SetterAccess,
     DAK_Lazy,
     DAK_StaticInitializeObjCMetadata,
-    DAK_RestatedObjCConformance
+    DAK_RestatedObjCConformance,
+    DAK_NonSendable,
   };
 
   return result;

lib/AST/Attr.cpp

@@ -874,6 +874,7 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
   case DAK_ReferenceOwnership:
   case DAK_Effects:
   case DAK_Optimize:
+  case DAK_NonSendable:
     if (DeclAttribute::isDeclModifier(getKind())) {
       Printer.printKeyword(getAttrName(), Options);
     } else if (Options.IsForSwiftInterface && getKind() == DAK_ResultBuilder) {

lib/Sema/TypeCheckConcurrency.cpp

@@ -3943,8 +3943,7 @@ NormalProtocolConformance *GetImplicitSendableRequest::evaluate(
     DeclContext *conformanceDC = nominal;
     if (attrMakingUnavailable) {
       llvm::VersionTuple NoVersion;
-      auto attr = new (ctx) AvailableAttr(attrMakingUnavailable->AtLoc,
-                                          attrMakingUnavailable->Range,
+      auto attr = new (ctx) AvailableAttr(SourceLoc(), SourceRange(),
                                           PlatformKind::none, "", "", nullptr,
                                           NoVersion, SourceRange(),
                                           NoVersion, SourceRange(),
@@ -3954,8 +3953,11 @@ NormalProtocolConformance *GetImplicitSendableRequest::evaluate(
 
       // Conformance availability is currently tied to the declaring extension.
       // FIXME: This is a hack--we should give conformances real availability.
+      auto inherits = ctx.AllocateCopy(makeArrayRef(
+          InheritedEntry(TypeLoc::withoutLoc(proto->getDeclaredInterfaceType()),
+                         /*isUnchecked*/true)));
       auto extension = ExtensionDecl::create(ctx, attrMakingUnavailable->AtLoc,
-                                             nullptr, {},
+                                             nullptr, inherits,
                                              nominal->getModuleScopeContext(),
                                              nullptr);
       extension->setImplicit();
@@ -3967,6 +3969,10 @@ NormalProtocolConformance *GetImplicitSendableRequest::evaluate(
                                 std::move(nominal));
       nominal->addExtension(extension);
 
+      // Make it accessible to getTopLevelDecls()
+      if (auto sf = dyn_cast<SourceFile>(nominal->getModuleScopeContext()))
+        sf->getOrCreateSynthesizedFile().addTopLevelDecl(extension);
+
       conformanceDC = extension;
     }
 

test/ModuleInterface/conformances.swift

@@ -237,6 +237,12 @@ public struct NestedAvailabilityOuter {
   public struct Inner: PrivateSubProto {}
 }
 
+@_nonSendable public struct NonSendable {}
+// NEGATIVE-NOT: @_nonSendable
+// CHECK-LABEL: public struct NonSendable {
+// CHECK: @available(*, unavailable)
+// CHECK-NEXT: extension conformances.NonSendable : @unchecked Swift.Sendable {
+
 // CHECK-END: @available(macOS 10.97, iOS 23, *)
 // CHECK-END: @available(tvOS, unavailable)
 // CHECK-END: extension conformances.NestedAvailabilityOuter.Inner : conformances.PublicBaseProto {}