[Serialization] Make package access-level compatible with deserialization safety

Author: xymus

lib/Serialization/Serialization.cpp

@@ -3146,7 +3146,7 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
     // A decl is safe if formally accessible publicly.
     auto accessScope = value->getFormalAccessScope(/*useDC=*/nullptr,
                        /*treatUsableFromInlineAsPublic=*/true);
-    if (accessScope.isPublic())
+    if (accessScope.isPublic() || accessScope.isPackage())
       return true;
 
     if (auto accessor = dyn_cast<AccessorDecl>(value))

test/Sema/package-only-references.swift

@@ -17,6 +17,11 @@
 // RUN:   -package-name MyPackage -I %t \
 // RUN:   -enable-experimental-feature AccessLevelOnImport
 
+// RUN: %target-swift-frontend -typecheck %t/Client.swift -I %t \
+// RUN:   -package-name MyPackage -I %t \
+// RUN:   -enable-deserialization-safety \
+// RUN:   -enable-experimental-feature AccessLevelOnImport
+
 /// A client outside of the package raises errors.
 // RUN: %target-swift-frontend -typecheck %t/Client.swift -I %t \
 // RUN:   -package-name NotMyPackage -I %t \