void ClassHierarchyAnalysis::init() {
  // Process all types implementing protocols.
  SmallVector<Decl *, 32> Decls;
  // TODO: It would be better if we could get all declarations
  // from a given module, not only the top-level ones.
  M->getSwiftModule()->getTopLevelDecls(Decls);

  NominalTypeWalker Walker(ProtocolImplementationsCache);
  for (auto *D: Decls) {
    D->walk(Walker);
  }

  // For each class declaration in our V-table list:
  for (auto &VT : M->getVTableList()) {
    ClassDecl *C = VT.getClass();
    // Ignore classes that are at the top of the class hierarchy:
    if (!C->hasSuperclass())
      continue;

    // Add the superclass to the list of inherited classes.
    ClassDecl *Super = C->getSuperclass()->getClassOrBoundGenericClass();
    auto &K = DirectSubclassesCache[Super];
    assert(std::find(K.begin(), K.end(), C) == K.end() &&
           "Class vector must be unique");
    K.push_back(C);
  }
}
static void lookupVisibleMemberDeclsImpl(
    Type BaseTy, VisibleDeclConsumer &Consumer, const DeclContext *CurrDC,
    LookupState LS, DeclVisibilityKind Reason, LazyResolver *TypeResolver,
    VisitedSet &Visited) {
  // Just look through l-valueness.  It doesn't affect name lookup.
  assert(BaseTy && "lookup into null type");
  BaseTy = BaseTy->getRValueType();

  // Handle metatype references, as in "some_type.some_member".  These are
  // special and can't have extensions.
  if (auto MTT = BaseTy->getAs<AnyMetatypeType>()) {
    // The metatype represents an arbitrary named type: dig through to the
    // declared type to see what we're dealing with.
    Type Ty = MTT->getInstanceType();

    // Just perform normal dot lookup on the type see if we find extensions or
    // anything else.  For example, type SomeTy.SomeMember can look up static
    // functions, and can even look up non-static functions as well (thus
    // getting the address of the member).
    lookupVisibleMemberDeclsImpl(Ty, Consumer, CurrDC,
                                 LookupState::makeQualified().withOnMetatype(),
                                 Reason, TypeResolver, Visited);
    return;
  }

  // Lookup module references, as on some_module.some_member.  These are
  // special and can't have extensions.
  if (ModuleType *MT = BaseTy->getAs<ModuleType>()) {
    AccessFilteringDeclConsumer FilteringConsumer(CurrDC, Consumer,
                                                  TypeResolver);
    MT->getModule()->lookupVisibleDecls(Module::AccessPathTy(),
                                        FilteringConsumer,
                                        NLKind::QualifiedLookup);
    return;
  }

  // If the base is a protocol, enumerate its members.
  if (ProtocolType *PT = BaseTy->getAs<ProtocolType>()) {
    lookupVisibleProtocolMemberDecls(BaseTy, PT, Consumer, CurrDC, LS, Reason,
                                     TypeResolver, Visited);
    return;
  }

  // If the base is a protocol composition, enumerate members of the protocols.
  if (auto PC = BaseTy->getAs<ProtocolCompositionType>()) {
    for (auto Proto : PC->getProtocols())
      lookupVisibleMemberDeclsImpl(Proto, Consumer, CurrDC, LS, Reason,
                                   TypeResolver, Visited);
    return;
  }

  // Enumerate members of archetype's requirements.
  if (ArchetypeType *Archetype = BaseTy->getAs<ArchetypeType>()) {
    for (auto Proto : Archetype->getConformsTo())
      lookupVisibleProtocolMemberDecls(
          BaseTy, Proto->getDeclaredType(), Consumer, CurrDC, LS,
          getReasonForSuper(Reason), TypeResolver, Visited);

    if (auto superclass = Archetype->getSuperclass())
      lookupVisibleMemberDeclsImpl(superclass, Consumer, CurrDC, LS,
                                   getReasonForSuper(Reason), TypeResolver,
                                   Visited);
    return;
  }

  do {
    NominalTypeDecl *CurNominal = BaseTy->getAnyNominal();
    if (!CurNominal)
      break;

    // Look in for members of a nominal type.
    lookupTypeMembers(BaseTy, BaseTy, Consumer, CurrDC, LS, Reason,
                      TypeResolver);
    lookupDeclsFromProtocolsBeingConformedTo(BaseTy, Consumer, LS, CurrDC,
                                             Reason, TypeResolver, Visited);
    // If we have a class type, look into its superclass.
    ClassDecl *CurClass = dyn_cast<ClassDecl>(CurNominal);

    if (CurClass && CurClass->hasSuperclass()) {
      assert(BaseTy.getPointer() != CurClass->getSuperclass().getPointer() &&
             "type is its own superclass");
      BaseTy = CurClass->getSuperclass();
      Reason = getReasonForSuper(Reason);

      bool InheritsSuperclassInitializers =
          CurClass->inheritsSuperclassInitializers(TypeResolver);
      if (LS.isOnSuperclass() && !InheritsSuperclassInitializers)
        LS = LS.withoutInheritsSuperclassInitializers();
      else if (!LS.isOnSuperclass()) {
        LS = LS.withOnSuperclass();
        if (InheritsSuperclassInitializers)
          LS = LS.withInheritsSuperclassInitializers();
      }
    } else {
      break;
    }
  } while (1);
}