swift-module-digester: diagnose type witness type changes when checking ABI stability.

include/swift/AST/DiagnosticsModuleDiffer.def

@@ -90,6 +90,8 @@ ERROR(func_self_access_change,none,"%0 has self access kind changing from %1 to
 
 ERROR(param_ownership_change,none,"%0 has %1 changing from %2 to %3", (StringRef, StringRef, StringRef, StringRef))
 
+ERROR(type_witness_change,none,"%0 has type witness type for %1 changing from %2 to %3", (StringRef, StringRef, StringRef, StringRef))
+
 #ifndef DIAG_NO_UNDEF
 # if defined(DIAG)
 #  undef DIAG

test/api-digester/Inputs/cake1.swift

@@ -150,3 +150,11 @@ public class FinalFuncContainer {
   public func NewFinalFunc() {}
   public final func NoLongerFinalFunc() {}
 }
+
+public protocol AssociatedTypesProtocol {
+  associatedtype T
+}
+
+public class TChangesFromIntToString: AssociatedTypesProtocol {
+  public typealias T = Int
+}

test/api-digester/Inputs/cake2.swift

@@ -161,3 +161,11 @@ public class FinalFuncContainer {
   public final func NewFinalFunc() {}
   public func NoLongerFinalFunc() {}
 }
+
+public protocol AssociatedTypesProtocol {
+  associatedtype T
+}
+
+public class TChangesFromIntToString: AssociatedTypesProtocol {
+  public typealias T = String
+}

test/api-digester/Outputs/Cake-abi.txt

@@ -27,6 +27,7 @@ cake1: Struct Somestruct2 has been renamed to Struct NSSomestruct2
 
 /* Type Changes */
 cake1: AssociatedType AssociatedTypePro.T3 has default type change from C1 to C6
+cake1: Class TChangesFromIntToString has type witness type for AssociatedTypesProtocol.T changing from Int to String
 cake1: Constructor S1.init(_:) has parameter 0 type change from Int to Double
 cake1: Func C1.foo2(_:) has parameter 0 type change from Int to () -> ()
 cake1: Func C7.foo(_:_:) has removed default argument from parameter 0

test/api-digester/Outputs/Cake.txt

@@ -32,6 +32,7 @@ cake1: Func C7.foo(_:_:) has removed default argument from parameter 0
 cake1: Func C7.foo(_:_:) has removed default argument from parameter 1
 cake1: Func ownershipChange(_:_:) has parameter 0 changing from InOut to Default
 cake1: Func ownershipChange(_:_:) has parameter 1 changing from Shared to Owned
+cake1: TypeAlias TChangesFromIntToString.T has underlying type change from Int to String
 
 /* Decl Attribute changes */
 cake1: Func C1.foo1() is now not static

tools/swift-api-digester/ModuleAnalyzerNodes.cpp

@@ -326,7 +326,7 @@ StringRef SDKNodeType::getParamValueOwnership() const {
 
 StringRef SDKNodeType::getTypeRoleDescription() const {
   assert(isTopLevelType());
-  auto P = cast<SDKNodeDecl>(getParent());
+  auto P = getParent();
   switch(P->getKind()) {
   case SDKNodeKind::Root:
   case SDKNodeKind::TypeNominal:
@@ -335,7 +335,6 @@ StringRef SDKNodeType::getTypeRoleDescription() const {
   case SDKNodeKind::DeclType:
   case SDKNodeKind::DeclOperator:
   case SDKNodeKind::Conformance:
-  case SDKNodeKind::TypeWitness:
     llvm_unreachable("Type Parent is wrong");
   case SDKNodeKind::DeclFunction:
   case SDKNodeKind::DeclConstructor:
@@ -350,6 +349,8 @@ StringRef SDKNodeType::getTypeRoleDescription() const {
     return "underlying";
   case SDKNodeKind::DeclAssociatedType:
     return "default";
+  case SDKNodeKind::TypeWitness:
+    return "type witness type";
   }
 }
 
@@ -376,14 +377,6 @@ StringRef SDKNodeDecl::getScreenInfo() const {
   return Ctx.buffer(OS.str());
 }
 
-bool SDKNodeDecl::isSDKPrivate() const {
-  if (getName().startswith("__"))
-    return true;
-  if (auto *PD = dyn_cast<SDKNodeDecl>(getParent()))
-    return PD->isSDKPrivate();
-  return false;
-}
-
 void SDKNodeDecl::printFullyQualifiedName(llvm::raw_ostream &OS) const {
   std::vector<NodePtr> Parent;
   for (auto *P = getParent(); isa<SDKNodeDecl>(P); P = P->getParent())
@@ -440,6 +433,11 @@ SDKNodeType *SDKNodeTypeWitness::getUnderlyingType() const {
   return getOnlyChild()->getAs<SDKNodeType>();
 }
 
+StringRef SDKNodeTypeWitness::getWitnessedTypeName() const {
+  return Ctx.buffer((llvm::Twine(getParent()->getAs<SDKNodeConformance>()->
+    getName()) + "." + getName()).str());
+}
+
 Optional<SDKNodeDeclType*> SDKNodeDeclType::getSuperclass() const {
   if (SuperclassUsr.empty())
     return None;

tools/swift-api-digester/ModuleAnalyzerNodes.h

@@ -320,7 +320,6 @@ class SDKNodeDecl: public SDKNode {
   DeclKind getDeclKind() const { return DKind; }
   void printFullyQualifiedName(llvm::raw_ostream &OS) const;
   StringRef getFullyQualifiedName() const;
-  bool isSDKPrivate() const;
   bool isDeprecated() const { return IsDeprecated; };
   bool isProtocolRequirement() const { return IsProtocolReq; }
   bool hasDeclAttribute(DeclAttrKind DAKind) const;
@@ -499,6 +498,7 @@ class SDKNodeConformance: public SDKNode {
 class SDKNodeTypeWitness: public SDKNode {
 public:
   SDKNodeTypeWitness(SDKNodeInitInfo Info);
+  StringRef getWitnessedTypeName() const;
   SDKNodeType *getUnderlyingType() const;
   static bool classof(const SDKNode *N);
 };

tools/swift-api-digester/ModuleDiagsConsumer.cpp

@@ -49,6 +49,7 @@ static StringRef getCategoryName(uint32_t ID) {
   case LocalDiagID::decl_type_change:
   case LocalDiagID::func_type_escaping_changed:
   case LocalDiagID::param_ownership_change:
+  case LocalDiagID::type_witness_change:
     return "/* Type Changes */";
   case LocalDiagID::raw_type_change:
     return "/* RawRepresentable Changes */";

tools/swift-api-digester/swift-api-digester.cpp

@@ -848,8 +848,7 @@ void swift::ide::api::SDKNodeDeclVar::diagnose(SDKNode *Right) {
 }
 
 static bool shouldDiagnoseType(SDKNodeType *T) {
-  return T->isTopLevelType() &&
-    !cast<SDKNodeDecl>(T->getParent())->isSDKPrivate();
+  return T->isTopLevelType();
 }
 
 void swift::ide::api::SDKNodeType::diagnose(SDKNode *Right) {
@@ -859,7 +858,21 @@ void swift::ide::api::SDKNodeType::diagnose(SDKNode *Right) {
   if (!RT || !shouldDiagnoseType(this))
     return;
   assert(isTopLevelType());
+
+  // Diagnose type witness changes when diagnosing ABI breakages.
+  if (auto *Wit = dyn_cast<SDKNodeTypeWitness>(getParent())) {
+    auto *Conform = Wit->getParent()->getAs<SDKNodeConformance>();
+    if (Ctx.checkingABI() && getPrintedName() != RT->getPrintedName()) {
+      Diags.diagnose(SourceLoc(), diag::type_witness_change,
+                     Conform->getNominalTypeDecl()->getScreenInfo(),
+                     Wit->getWitnessedTypeName(),
+                     getPrintedName(), RT->getPrintedName());
+    }
+    return;
+  }
+
   StringRef Descriptor = getTypeRoleDescription();
+  assert(isa<SDKNodeDecl>(getParent()));
   auto LParent = cast<SDKNodeDecl>(getParent());
   assert(LParent->getKind() == RT->getParent()->getAs<SDKNodeDecl>()->getKind());
 
@@ -1900,8 +1913,6 @@ void DiagnosisEmitter::handle(const SDKNodeDecl *Node, NodeAnnotation Anno) {
 }
 
 void DiagnosisEmitter::visitDecl(SDKNodeDecl *Node) {
-  if (Node->isSDKPrivate())
-    return;
   std::vector<NodeAnnotation> Scratch;
   for (auto Anno : Node->getAnnotations(Scratch))
     handle(Node, Anno);