[Name lookup] Introduce a request for "extended nominal type decl"

include/swift/AST/Decl.h

@@ -1640,7 +1640,10 @@ class ExtensionDecl final : public GenericContext, public Decl,
 
   /// The type being extended.
   TypeLoc ExtendedType;
-
+
+  /// The nominal type being extended.
+  NominalTypeDecl *ExtendedNominal = nullptr;
+
   MutableArrayRef<TypeLoc> Inherited;
 
   /// \brief The next extension in the linked list of extensions.
@@ -1677,6 +1680,7 @@ class ExtensionDecl final : public GenericContext, public Decl,
   /// Slow path for \c takeConformanceLoader().
   std::pair<LazyMemberLoader *, uint64_t> takeConformanceLoaderSlow();
 
+  friend class ExtendedNominalRequest;
 public:
   using Decl::getASTContext;
 
@@ -1698,8 +1702,19 @@ class ExtensionDecl final : public GenericContext, public Decl,
   void setBraces(SourceRange braces) { Braces = braces; }
 
   /// Retrieve the type being extended.
+  ///
+  /// Only use this entry point when the complete type, as spelled in the source,
+  /// is required. For most clients, \c getExtendedNominal(), which provides
+  /// only the \c NominalTypeDecl, will suffice.
   Type getExtendedType() const { return ExtendedType.getType(); }
 
+  /// Retrieve the nominal type declaration that is being extended.
+  NominalTypeDecl *getExtendedNominal() const;
+
+  /// Determine whether this extension has already been bound to a nominal
+  /// type declaration.
+  bool alreadyBoundToNominal() const { return NextExtension.getInt(); }
+
   /// Retrieve the extended type location.
   TypeLoc &getExtendedTypeLoc() { return ExtendedType; }
 
@@ -3615,6 +3630,23 @@ class ClassDecl final : public NominalTypeDecl {
   /// might have implicitly @objc members, but will never itself be @objc.
   ObjCClassKind checkObjCAncestry() const;
 
+  /// \brief Whether this class or its superclasses has some form of generic
+  /// context.
+  ///
+  /// For example, given
+  ///
+  /// class A<X> {}
+  /// class B : A<Int> {}
+  /// struct C<T> {
+  ///   struct Inner {}
+  /// }
+  /// class D {}
+  /// class E: D {}
+  ///
+  /// Calling hasGenericAncestry() on `B` returns `A<Int>`, on `C<T>.Inner`
+  /// returns `C<T>.Inner`, but on `E` it returns null.
+  ClassDecl *getGenericAncestor() const;
+
   /// The type of metaclass to use for a class.
   enum class MetaclassKind : uint8_t {
     ObjC,
@@ -3679,7 +3711,7 @@ class ClassDecl final : public NominalTypeDecl {
   ///
   /// This is true of imported Objective-C classes.
   bool usesObjCGenericsModel() const {
-    return isObjC() && hasClangNode() && isGenericContext();
+    return hasClangNode() && isGenericContext() && isObjC();
   }
 
   /// True if the class is known to be implemented in Swift.

include/swift/AST/DiagnosticsSema.def

@@ -1490,7 +1490,8 @@ ERROR(extension_specialization,none,
 ERROR(extension_stored_property,none,
       "extensions must not contain stored properties", ())
 ERROR(extension_nongeneric_trailing_where,none,
-      "trailing 'where' clause for extension of non-generic type %0", (Type))
+      "trailing 'where' clause for extension of non-generic type %0",
+      (DeclName))
 ERROR(extension_protocol_inheritance,none,
       "extension of protocol %0 cannot have an inheritance clause", (Type))
 ERROR(objc_generic_extension_using_type_parameter,none,

include/swift/AST/NameLookupRequests.h

@@ -157,6 +157,33 @@ class SuperclassDeclRequest :
   void noteCycleStep(DiagnosticEngine &diags) const;
 };
 
+/// Request the nominal declaration extended by a given extension declaration.
+class ExtendedNominalRequest :
+    public SimpleRequest<ExtendedNominalRequest,
+                         CacheKind::SeparatelyCached,
+                         NominalTypeDecl *,
+                         ExtensionDecl *> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend class SimpleRequest;
+
+  // Evaluation.
+  NominalTypeDecl *evaluate(Evaluator &evaluator, ExtensionDecl *ext) const;
+
+public:
+  // Separate caching.
+  bool isCached() const { return true; }
+  Optional<NominalTypeDecl *> getCachedResult() const;
+  void cacheResult(NominalTypeDecl *value) const;
+
+  // Cycle handling
+  NominalTypeDecl *breakCycle() const { return nullptr; }
+  void diagnoseCycle(DiagnosticEngine &diags) const;
+  void noteCycleStep(DiagnosticEngine &diags) const;
+};
+
 /// The zone number for name-lookup requests.
 #define SWIFT_NAME_LOOKUP_REQUESTS_TYPEID_ZONE 9
 

include/swift/AST/NameLookupTypeIDZone.def

@@ -17,3 +17,4 @@
 SWIFT_TYPEID(InheritedDeclsReferencedRequest)
 SWIFT_TYPEID(UnderlyingTypeDeclsReferencedRequest)
 SWIFT_TYPEID(SuperclassDeclRequest)
+SWIFT_TYPEID(ExtendedNominalRequest)

include/swift/AST/Types.h

@@ -806,23 +806,6 @@ class alignas(1 << TypeAlignInBits) TypeBase {
   Type getSuperclassForDecl(const ClassDecl *classDecl,
                             bool useArchetypes = true);
 
-  /// \brief Whether this type or its superclasses has some form of generic
-  /// context.
-  ///
-  /// For example, given
-  ///
-  /// class A<X> {}
-  /// class B : A<Int> {}
-  /// struct C<T> {
-  ///   struct Inner {}
-  /// }
-  /// class D {}
-  /// class E: D {}
-  ///
-  /// Calling hasGenericAncestry() on `B` returns `A<Int>`, on `C<T>.Inner`
-  /// returns `C<T>.Inner`, but on `E` it returns null.
-  Type getGenericAncestor();
-
   /// \brief True if this type is the superclass of another type, or a generic
   /// type that could be bound to the superclass.
   ///

lib/AST/ASTDumper.cpp

@@ -1295,11 +1295,8 @@ void swift::printContext(raw_ostream &os, DeclContext *dc) {
     break;
 
   case DeclContextKind::ExtensionDecl:
-    if (auto extendedTy = cast<ExtensionDecl>(dc)->getExtendedType()) {
-      if (auto nominal = extendedTy->getAnyNominal()) {
-        printName(os, nominal->getName());
-        break;
-      }
+    if (auto extendedNominal = cast<ExtensionDecl>(dc)->getExtendedNominal()) {
+      printName(os, extendedNominal->getName());
     }
     os << " extension";
     break;

lib/AST/ASTMangler.cpp

@@ -1402,13 +1402,11 @@ void ASTMangler::appendContext(const DeclContext *ctx) {
 
   case DeclContextKind::ExtensionDecl: {
     auto ExtD = cast<ExtensionDecl>(ctx);
-    auto ExtTy = ExtD->getExtendedType();
+    auto decl = ExtD->getExtendedNominal();
     // Recover from erroneous extension.
-    if (ExtTy.isNull() || ExtTy->hasError())
+    if (!decl)
       return appendContext(ExtD->getDeclContext());
 
-    auto decl = ExtTy->getAnyNominal();
-    assert(decl && "extension of non-nominal type?");
     if (!ExtD->isEquivalentToExtendedContext()) {
     // Mangle the extension if:
     // - the extension is defined in a different module from the original

lib/AST/ASTPrinter.cpp

@@ -1817,8 +1817,7 @@ void PrintAST::printExtension(ExtensionDecl *decl) {
     recordDeclLoc(decl, [&]{
       // We cannot extend sugared types.
       Type extendedType = decl->getExtendedType();
-      NominalTypeDecl *nominal = extendedType ? extendedType->getAnyNominal() : nullptr;
-      if (!nominal) {
+      if (!extendedType || !extendedType->getAnyNominal()) {
         // Fallback to TypeRepr.
         printTypeLoc(decl->getExtendedTypeLoc());
         return;

lib/AST/ASTScope.cpp

@@ -1760,11 +1760,6 @@ SmallVector<ValueDecl *, 4> ASTScope::getLocalBindings() const {
     if (range.Start == range.End)
       break;
 
-    // Bind this extension, if we haven't done so already.
-    if (!extension->getExtendedType())
-      if (auto resolver = extension->getASTContext().getLazyResolver())
-        resolver->bindExtension(extension);
-
     // If there are generic parameters, add them.
     for (auto genericParams = extension->getGenericParams();
          genericParams;
@@ -1915,8 +1910,8 @@ void ASTScope::print(llvm::raw_ostream &out, unsigned level,
     out << " extension of '";
     if (auto typeRepr = extension->getExtendedTypeLoc().getTypeRepr())
       typeRepr->print(out);
-    else
-      extension->getExtendedType()->print(out);
+    else if (auto nominal = extension->getExtendedNominal())
+      out << nominal->getName();
     out << "'";
     printRange();
     break;

lib/AST/ASTVerifier.cpp

@@ -2471,7 +2471,7 @@ class Verifier : public ASTWalker {
       } else {
         auto ext = cast<ExtensionDecl>(decl);
         conformingDC = ext;
-        nominal = ext->getExtendedType()->getAnyNominal();
+        nominal = ext->getExtendedNominal();
       }
 
       auto proto = conformance->getProtocol();
@@ -2619,8 +2619,14 @@ class Verifier : public ASTWalker {
       verifyProtocolList(nominal, nominal->getLocalProtocols());
 
       // Make sure that the protocol conformances are complete.
-      for (auto conformance : nominal->getLocalConformances()) {
-        verifyConformance(nominal, conformance);
+      // Only do so within the source file of the nominal type,
+      // because anywhere else this can trigger new type-check requests.
+      if (auto sf = M.dyn_cast<SourceFile *>()) {
+        if (nominal->getParentSourceFile() == sf) {
+          for (auto conformance : nominal->getLocalConformances()) {
+            verifyConformance(nominal, conformance);
+          }
+        }
       }
 
       verifyCheckedBase(nominal);
@@ -3491,7 +3497,7 @@ void swift::verify(SourceFile &SF) {
 bool swift::shouldVerify(const Decl *D, const ASTContext &Context) {
 #if !(defined(NDEBUG) || defined(SWIFT_DISABLE_AST_VERIFIER))
   if (const auto *ED = dyn_cast<ExtensionDecl>(D)) {
-    return shouldVerify(ED->getExtendedType()->getAnyNominal(), Context);
+    return shouldVerify(ED->getExtendedNominal(), Context);
   }
 
   const auto *VD = dyn_cast<ValueDecl>(D);

lib/AST/AccessRequests.cpp

@@ -206,12 +206,9 @@ DefaultAndMaxAccessLevelRequest::evaluate(Evaluator &evaluator,
 
   AccessLevel maxAccess = AccessLevel::Public;
 
-  if (!ED->getExtendedType().isNull() &&
-      !ED->getExtendedType()->hasError()) {
-    if (NominalTypeDecl *nominal = ED->getExtendedType()->getAnyNominal()) {
-      maxAccess = std::max(nominal->getFormalAccess(),
-                           AccessLevel::FilePrivate);
-    }
+  if (NominalTypeDecl *nominal = ED->getExtendedNominal()) {
+    maxAccess = std::max(nominal->getFormalAccess(),
+                         AccessLevel::FilePrivate);
   }
 
   if (const GenericParamList *genericParams = ED->getGenericParams()) {

lib/AST/ConformanceLookupTable.cpp

@@ -865,6 +865,11 @@ ConformanceLookupTable::getConformance(NominalTypeDecl *nominal,
         ctx.getInheritedConformance(type, inheritedConformance->getConcrete());
   } else {
     // Create or find the normal conformance.
+    if (auto ext = dyn_cast<ExtensionDecl>(conformingDC)) {
+      if (auto resolver = ctx.getLazyResolver())
+        resolver->bindExtension(ext);
+    }
+
     Type conformingType = conformingDC->getDeclaredInterfaceType();
     SourceLoc conformanceLoc
       = conformingNominal == conformingDC

lib/AST/Decl.cpp

@@ -981,6 +981,12 @@ ExtensionDecl::takeConformanceLoaderSlow() {
   return { contextInfo->loader, contextInfo->allConformancesData };
 }
 
+NominalTypeDecl *ExtensionDecl::getExtendedNominal() const {
+  ASTContext &ctx = getASTContext();
+  return ctx.evaluator(
+      ExtendedNominalRequest{const_cast<ExtensionDecl *>(this)});;
+}
+
 Type ExtensionDecl::getInheritedType(unsigned index) const {
   ASTContext &ctx = getASTContext();
   return ctx.evaluator(InheritedTypeRequest{const_cast<ExtensionDecl *>(this),
@@ -992,7 +998,7 @@ bool ExtensionDecl::isConstrainedExtension() const {
   if (!getGenericSignature())
     return false;
 
-  auto nominal = getExtendedType()->getAnyNominal();
+  auto nominal = getExtendedNominal();
   assert(nominal);
 
   // If the generic signature differs from that of the nominal type, it's a
@@ -1002,7 +1008,7 @@ bool ExtensionDecl::isConstrainedExtension() const {
 }
 
 bool ExtensionDecl::isEquivalentToExtendedContext() const {
-  auto decl = getExtendedType()->getAnyNominal();
+  auto decl = getExtendedNominal();
   return getParentModule() == decl->getParentModule()
     && !isConstrainedExtension()
     && !getDeclaredInterfaceType()->isExistentialType();
@@ -2373,11 +2379,9 @@ AccessLevel ValueDecl::getEffectiveAccess() const {
   } else if (auto enclosingExt = dyn_cast<ExtensionDecl>(getDeclContext())) {
     // Just check the base type. If it's a constrained extension, Sema should
     // have already enforced access more strictly.
-    if (auto extendedTy = enclosingExt->getExtendedType()) {
-      if (auto nominal = extendedTy->getAnyNominal()) {
-        effectiveAccess =
-            restrictToEnclosing(effectiveAccess, nominal->getEffectiveAccess());
-      }
+    if (auto nominal = enclosingExt->getExtendedNominal()) {
+      effectiveAccess =
+          restrictToEnclosing(effectiveAccess, nominal->getEffectiveAccess());
     }
 
   } else if (getDeclContext()->isLocalContext()) {
@@ -2430,13 +2434,11 @@ getAccessScopeForFormalAccess(const ValueDecl *VD,
     } else if (auto enclosingExt = dyn_cast<ExtensionDecl>(resultDC)) {
       // Just check the base type. If it's a constrained extension, Sema should
       // have already enforced access more strictly.
-      if (auto extendedTy = enclosingExt->getExtendedType()) {
-        if (auto nominal = extendedTy->getAnyNominal()) {
-          auto nominalAccess =
-              getAdjustedFormalAccess(nominal, useDC,
-                                      treatUsableFromInlineAsPublic);
-          access = std::min(access, nominalAccess);
-        }
+      if (auto nominal = enclosingExt->getExtendedNominal()) {
+        auto nominalAccess =
+            getAdjustedFormalAccess(nominal, useDC,
+                                    treatUsableFromInlineAsPublic);
+        access = std::min(access, nominalAccess);
       }
 
     } else {
@@ -2881,7 +2883,7 @@ ExtensionRange NominalTypeDecl::getExtensions() {
 }
 
 void NominalTypeDecl::addExtension(ExtensionDecl *extension) {
-  assert(!extension->NextExtension.getInt() && "Already added extension");
+  assert(!extension->alreadyBoundToNominal() && "Already added extension");
   extension->NextExtension.setInt(true);
 
   // First extension; set both first and last.
@@ -3374,6 +3376,18 @@ ClassDecl::findImplementingMethod(const AbstractFunctionDecl *Method) const {
   return nullptr;
 }
 
+ClassDecl *ClassDecl::getGenericAncestor() const {
+  ClassDecl *current = const_cast<ClassDecl *>(this);
+
+  while (current) {
+    if (current->isGenericContext())
+      return current;
+
+    current = current->getSuperclassDecl();
+  }
+
+  return nullptr;
+}
 
 EnumCaseDecl *EnumCaseDecl::create(SourceLoc CaseLoc,
                                    ArrayRef<EnumElementDecl *> Elements,