ABIChecker: diagnose moving a non-final member from a class to an extension to the class

rdar://93498817

Author: nkcsgexi

include/swift/APIDigester/ModuleAnalyzerNodes.h

@@ -712,6 +712,7 @@ class SDKNodeDeclConstructor: public SDKNodeDeclAbstractFunc {
   void jsonize(json::Output &Out) override;
 };
 
+// Note: Accessor doesn't have Parent pointer.
 class SDKNodeDeclAccessor: public SDKNodeDeclAbstractFunc {
   SDKNodeDecl *Owner;
   AccessorKind AccKind;
@@ -830,6 +831,8 @@ int findDeclUsr(StringRef dumpPath, CheckerOptions Opts);
 
 void nodeSetDifference(ArrayRef<SDKNode*> Left, ArrayRef<SDKNode*> Right,
   NodeVector &LeftMinusRight, NodeVector &RightMinusLeft);
+
+bool hasValidParentPtr(SDKNodeKind kind);
 } // end of abi namespace
 } // end of ide namespace
 } // end of Swift namespace

include/swift/AST/DiagnosticsModuleDiffer.def

@@ -76,6 +76,8 @@ ERROR(type_witness_change,APIDigesterBreakage,"%0 has type witness type for %1 c
 
 ERROR(decl_new_witness_table_entry,APIDigesterBreakage,"%0 now requires%select{| no}1 new witness table entry", (StringRef, bool))
 
+ERROR(class_member_moved_to_extension,APIDigesterBreakage,"Non-final class member %0 is moved to extension", (StringRef))
+
 WARNING(new_decl_without_intro,APIDigesterBreakage,"%0 is a new API without @available attribute", (StringRef))
 
 ERROR(objc_name_change,APIDigesterBreakage,"%0 has ObjC name change from %1 to %2", (StringRef, StringRef, StringRef))

lib/APIDigester/ModuleAnalyzerNodes.cpp

@@ -54,6 +54,16 @@ struct swift::ide::api::SDKNodeInitInfo {
   SDKNode* createSDKNode(SDKNodeKind Kind);
 };
 
+bool swift::ide::api::hasValidParentPtr(SDKNodeKind kind) {
+  switch(kind) {
+  case SDKNodeKind::Conformance:
+  case SDKNodeKind::DeclAccessor:
+    return false;
+  default:
+    return true;
+  }
+}
+
 SDKContext::SDKContext(CheckerOptions Opts): Diags(SourceMgr), Opts(Opts) {}
 
 DiagnosticEngine &SDKContext::getDiags(SourceLoc Loc) {
@@ -827,6 +837,25 @@ static bool hasSameParameterFlags(const SDKNodeType *Left, const SDKNodeType *Ri
   return true;
 }
 
+// Return whether a decl has been moved in/out to an extension
+static Optional<bool> isFromExtensionChanged(const SDKNode &L, const SDKNode &R) {
+  assert(L.getKind() == R.getKind());
+  // Version 8 starts to include whether a decl is from an extension.
+  if (L.getJsonFormatVersion() + R.getJsonFormatVersion() < 2 * 8) {
+    return llvm::None;
+  }
+  auto *Left = dyn_cast<SDKNodeDecl>(&L);
+  auto *Right = dyn_cast<SDKNodeDecl>(&R);
+  if (!Left) {
+    return llvm::None;
+  }
+  if (Left->isFromExtension() == Right->isFromExtension()) {
+    return llvm::None;
+  } else {
+    return Right->isFromExtension();
+  }
+}
+
 static bool isSDKNodeEqual(SDKContext &Ctx, const SDKNode &L, const SDKNode &R) {
   auto *LeftAlias = dyn_cast<SDKNodeTypeAlias>(&L);
   auto *RightAlias = dyn_cast<SDKNodeTypeAlias>(&R);
@@ -966,6 +995,8 @@ static bool isSDKNodeEqual(SDKContext &Ctx, const SDKNode &L, const SDKNode &R)
     case SDKNodeKind::TypeWitness:
     case SDKNodeKind::DeclImport:
     case SDKNodeKind::Root: {
+      if (isFromExtensionChanged(L, R))
+        return false;
       return L.getPrintedName() == R.getPrintedName() &&
         L.hasSameChildren(R);
     }
@@ -2619,6 +2650,23 @@ void swift::ide::api::SDKNodeDeclAbstractFunc::diagnose(SDKNode *Right) {
     if (reqNewWitnessTableEntry() != R->reqNewWitnessTableEntry()) {
       emitDiag(Loc, diag::decl_new_witness_table_entry, reqNewWitnessTableEntry());
     }
+
+    // Diagnose moving a non-final class member to an extension.
+    if (hasValidParentPtr(getKind())) {
+      while(auto *parent = dyn_cast<SDKNodeDecl>(getParent())) {
+        if (parent->getDeclKind() != DeclKind::Class) {
+          break;
+        }
+        if (hasDeclAttribute(DeclAttrKind::DAK_Final)) {
+          break;
+        }
+        auto result = isFromExtensionChanged(*this, *Right);
+        if (result.hasValue() && *result) {
+          emitDiag(Loc, diag::class_member_moved_to_extension);
+        }
+        break;
+      }
+    }
   }
 }
 

test/api-digester/move-to-extension.swift

@@ -0,0 +1,23 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -emit-module -o %t/Foo.swiftmodule -emit-abi-descriptor-path %t/abi-before.json %s -enable-library-evolution -DBASELINE -emit-tbd-path %t/abi-before.tbd
+// RUN: %target-swift-frontend -emit-module -o %t/Foo.swiftmodule -emit-abi-descriptor-path %t/abi-after.json %s -enable-library-evolution -emit-tbd-path %t/abi-after.tbd
+// RUN: %api-digester -diagnose-sdk --input-paths %t/abi-before.json -input-paths %t/abi-after.json -abi -o %t/result.txt
+// RUN: %FileCheck %s < %t/result.txt
+
+#if BASELINE
+
+public class C {
+	public func foo() {}
+}
+
+#else
+
+public class C {}
+extension C {
+	public func foo() {}
+}
+
+#endif
+
+// CHECK: Non-final class member Func C.foo() is moved to extension