//===--- SemaCXXScopeSpec.cpp - Semantic Analysis for C++ scope specifiers-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file implements C++ semantic analysis for scope specifiers.

//

//===----------------------------------------------------------------------===//

#include "TypeLocBuilder.h"

#include "clang/AST/ASTContext.h"

#include "clang/AST/DeclTemplate.h"

#include "clang/AST/ExprCXX.h"

#include "clang/AST/NestedNameSpecifier.h"

#include "clang/Basic/PartialDiagnostic.h"

#include "clang/Sema/DeclSpec.h"

#include "clang/Sema/Lookup.h"

#include "clang/Sema/SemaInternal.h"

#include "clang/Sema/Template.h"

#include "llvm/ADT/STLExtras.h"

using namespace clang;

/// Find the current instantiation that associated with the given type.

static CXXRecordDecl *getCurrentInstantiationOf(QualType T,

                                                DeclContext *CurContext) {

  if (T.isNull())

    return nullptr;

  const Type *Ty = T->getCanonicalTypeInternal().getTypePtr();

  if (const RecordType *RecordTy = dyn_cast<RecordType>(Ty)) {

    CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl());

    if (!Record->isDependentContext() ||

        Record->isCurrentInstantiation(CurContext))

      return Record;

    return nullptr;

  } else if (isa<InjectedClassNameType>(Ty))

    return cast<InjectedClassNameType>(Ty)->getDecl();

  else

    return nullptr;

}

/// Compute the DeclContext that is associated with the given type.

///

/// \param T the type for which we are attempting to find a DeclContext.

///

/// \returns the declaration context represented by the type T,

/// or NULL if the declaration context cannot be computed (e.g., because it is

/// dependent and not the current instantiation).

DeclContext *Sema::computeDeclContext(QualType T) {

  if (!T->isDependentType())

    if (const TagType *Tag = T->getAs<TagType>())

      return Tag->getDecl();

  return ::getCurrentInstantiationOf(T, CurContext);

}

/// Compute the DeclContext that is associated with the given

/// scope specifier.

///

/// \param SS the C++ scope specifier as it appears in the source

///

/// \param EnteringContext when true, we will be entering the context of

/// this scope specifier, so we can retrieve the declaration context of a

/// class template or class template partial specialization even if it is

/// not the current instantiation.

///

/// \returns the declaration context represented by the scope specifier @p SS,

/// or NULL if the declaration context cannot be computed (e.g., because it is

/// dependent and not the current instantiation).

DeclContext *Sema::computeDeclContext(const CXXScopeSpec &SS,

                                      bool EnteringContext) {

  if (!SS.isSet() || SS.isInvalid())

    return nullptr;

  NestedNameSpecifier *NNS = SS.getScopeRep();

  if (NNS->isDependent()) {

    // If this nested-name-specifier refers to the current

    // instantiation, return its DeclContext.

    if (CXXRecordDecl *Record = getCurrentInstantiationOf(NNS))

      return Record;

    if (EnteringContext) {

      const Type *NNSType = NNS->getAsType();

      if (!NNSType) {

        return nullptr;

      }

      // Look through type alias templates, per C++0x [temp.dep.type]p1.

      NNSType = Context.getCanonicalType(NNSType);

      if (const TemplateSpecializationType *SpecType

            = NNSType->getAs<TemplateSpecializationType>()) {

        // We are entering the context of the nested name specifier, so try to

        // match the nested name specifier to either a primary class template

        // or a class template partial specialization.

        if (ClassTemplateDecl *ClassTemplate

              = dyn_cast_or_null<ClassTemplateDecl>(

                            SpecType->getTemplateName().getAsTemplateDecl())) {

          QualType ContextType =

              Context.getCanonicalType(QualType(SpecType, 0));

          // FIXME: The fallback on the search of partial

          // specialization using ContextType should be eventually removed since

          // it doesn't handle the case of constrained template parameters

          // correctly. Currently removing this fallback would change the

          // diagnostic output for invalid code in a number of tests.

          ClassTemplatePartialSpecializationDecl *PartialSpec = nullptr;

          ArrayRef<TemplateParameterList *> TemplateParamLists =

              SS.getTemplateParamLists();

          if (!TemplateParamLists.empty()) {

            unsigned Depth = ClassTemplate->getTemplateParameters()->getDepth();

            auto L = find_if(TemplateParamLists,

                             [Depth](TemplateParameterList *TPL) {

                               return TPL->getDepth() == Depth;

                             });

            if (L != TemplateParamLists.end()) {

              void *Pos = nullptr;

              PartialSpec = ClassTemplate->findPartialSpecialization(

                  SpecType->template_arguments(), *L, Pos);

            }

          } else {

            PartialSpec = ClassTemplate->findPartialSpecialization(ContextType);

          }

          if (PartialSpec) {

            // A declaration of the partial specialization must be visible.

            // We can always recover here, because this only happens when we're

            // entering the context, and that can't happen in a SFINAE context.

            assert(!isSFINAEContext() && "partial specialization scope "

                                         "specifier in SFINAE context?");

            if (PartialSpec->hasDefinition() &&

                !hasReachableDefinition(PartialSpec))

              diagnoseMissingImport(SS.getLastQualifierNameLoc(), PartialSpec,

                                    MissingImportKind::PartialSpecialization,

                                    true);

            return PartialSpec;

          }

          // If the type of the nested name specifier is the same as the

          // injected class name of the named class template, we're entering

          // into that class template definition.

          QualType Injected =

              ClassTemplate->getInjectedClassNameSpecialization();

          if (Context.hasSameType(Injected, ContextType))

            return ClassTemplate->getTemplatedDecl();

        }

      } else if (const RecordType *RecordT = NNSType->getAs<RecordType>()) {

        // The nested name specifier refers to a member of a class template.

        return RecordT->getDecl();

      }

    }

    return nullptr;

  }

  switch (NNS->getKind()) {

  case NestedNameSpecifier::Identifier:

    llvm_unreachable("Dependent nested-name-specifier has no DeclContext");

  case NestedNameSpecifier::Namespace:

    return NNS->getAsNamespace();

  case NestedNameSpecifier::NamespaceAlias:

    return NNS->getAsNamespaceAlias()->getNamespace();

  case NestedNameSpecifier::TypeSpec:

  case NestedNameSpecifier::TypeSpecWithTemplate: {

    const TagType *Tag = NNS->getAsType()->getAs<TagType>();

    assert(Tag && "Non-tag type in nested-name-specifier");

    return Tag->getDecl();

  }

  case NestedNameSpecifier::Global:

    return Context.getTranslationUnitDecl();

  case NestedNameSpecifier::Super:

    return NNS->getAsRecordDecl();

  }

  llvm_unreachable("Invalid NestedNameSpecifier::Kind!");

}

bool Sema::isDependentScopeSpecifier(const CXXScopeSpec &SS) {

  if (!SS.isSet() || SS.isInvalid())

    return false;

  return SS.getScopeRep()->isDependent();

}

/// If the given nested name specifier refers to the current

/// instantiation, return the declaration that corresponds to that

/// current instantiation (C++0x [temp.dep.type]p1).

///

/// \param NNS a dependent nested name specifier.

CXXRecordDecl *Sema::getCurrentInstantiationOf(NestedNameSpecifier *NNS) {

  assert(getLangOpts().CPlusPlus && "Only callable in C++");

  assert(NNS->isDependent() && "Only dependent nested-name-specifier allowed");

  if (!NNS->getAsType())

    return nullptr;

  QualType T = QualType(NNS->getAsType(), 0);

  return ::getCurrentInstantiationOf(T, CurContext);

}

/// Require that the context specified by SS be complete.

///

/// If SS refers to a type, this routine checks whether the type is

/// complete enough (or can be made complete enough) for name lookup

/// into the DeclContext. A type that is not yet completed can be

/// considered "complete enough" if it is a class/struct/union/enum

/// that is currently being defined. Or, if we have a type that names

/// a class template specialization that is not a complete type, we

/// will attempt to instantiate that class template.

bool Sema::RequireCompleteDeclContext(CXXScopeSpec &SS,

                                      DeclContext *DC) {

  assert(DC && "given null context");

  TagDecl *tag = dyn_cast<TagDecl>(DC);

  // If this is a dependent type, then we consider it complete.

  // FIXME: This is wrong; we should require a (visible) definition to

  // exist in this case too.

  if (!tag || tag->isDependentContext())

    return false;

  // Grab the tag definition, if there is one.

  QualType type = Context.getTypeDeclType(tag);

  tag = type->getAsTagDecl();

  // If we're currently defining this type, then lookup into the

  // type is okay: don't complain that it isn't complete yet.

  if (tag->isBeingDefined())

    return false;

  SourceLocation loc = SS.getLastQualifierNameLoc();

  if (loc.isInvalid()) loc = SS.getRange().getBegin();

  // The type must be complete.

  if (RequireCompleteType(loc, type, diag::err_incomplete_nested_name_spec,

                          SS.getRange())) {

    SS.SetInvalid(SS.getRange());

    return true;

  }

  if (auto *EnumD = dyn_cast<EnumDecl>(tag))

    // Fixed enum types and scoped enum instantiations are complete, but they

    // aren't valid as scopes until we see or instantiate their definition.

    return RequireCompleteEnumDecl(EnumD, loc, &SS);

  return false;

}

/// Require that the EnumDecl is completed with its enumerators defined or

/// instantiated. SS, if provided, is the ScopeRef parsed.

///

bool Sema::RequireCompleteEnumDecl(EnumDecl *EnumD, SourceLocation L,

                                   CXXScopeSpec *SS) {

  if (EnumD->isCompleteDefinition()) {

    // If we know about the definition but it is not visible, complain.

    NamedDecl *SuggestedDef = nullptr;

    if (!hasReachableDefinition(EnumD, &SuggestedDef,

                                /*OnlyNeedComplete*/ false)) {

      // If the user is going to see an error here, recover by making the

      // definition visible.

      bool TreatAsComplete = !isSFINAEContext();

      diagnoseMissingImport(L, SuggestedDef, MissingImportKind::Definition,

                            /*Recover*/ TreatAsComplete);

      return !TreatAsComplete;

    }

    return false;

  }

  // Try to instantiate the definition, if this is a specialization of an

  // enumeration temploid.

  if (EnumDecl *Pattern = EnumD->getInstantiatedFromMemberEnum()) {

    MemberSpecializationInfo *MSI = EnumD->getMemberSpecializationInfo();

    if (MSI->getTemplateSpecializationKind() != TSK_ExplicitSpecialization) {

      if (InstantiateEnum(L, EnumD, Pattern,

                          getTemplateInstantiationArgs(EnumD),

                          TSK_ImplicitInstantiation)) {

        if (SS)

          SS->SetInvalid(SS->getRange());

        return true;

      }

      return false;

    }

  }

  if (SS) {

    Diag(L, diag::err_incomplete_nested_name_spec)

        << QualType(EnumD->getTypeForDecl(), 0) << SS->getRange();

    SS->SetInvalid(SS->getRange());

  } else {

    Diag(L, diag::err_incomplete_enum) << QualType(EnumD->getTypeForDecl(), 0);

    Diag(EnumD->getLocation(), diag::note_declared_at);

  }

  return true;

}

bool Sema::ActOnCXXGlobalScopeSpecifier(SourceLocation CCLoc,

                                        CXXScopeSpec &SS) {

  SS.MakeGlobal(Context, CCLoc);

  return false;

}

bool Sema::ActOnSuperScopeSpecifier(SourceLocation SuperLoc,

                                    SourceLocation ColonColonLoc,

                                    CXXScopeSpec &SS) {

  if (getCurLambda()) {

    Diag(SuperLoc, diag::err_super_in_lambda_unsupported);

    return true;

  }

  CXXRecordDecl *RD = nullptr;

  for (Scope *S = getCurScope(); S; S = S->getParent()) {

    if (S->isFunctionScope()) {

      if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(S->getEntity()))

        RD = MD->getParent();

      break;

    }

    if (S->isClassScope()) {

      RD = cast<CXXRecordDecl>(S->getEntity());

      break;

    }

  }

  if (!RD) {

    Diag(SuperLoc, diag::err_invalid_super_scope);

    return true;

  } else if (RD->getNumBases() == 0) {

    Diag(SuperLoc, diag::err_no_base_classes) << RD->getName();

    return true;

  }

  SS.MakeSuper(Context, RD, SuperLoc, ColonColonLoc);

  return false;

}

/// Determines whether the given declaration is an valid acceptable

/// result for name lookup of a nested-name-specifier.

/// \param SD Declaration checked for nested-name-specifier.

/// \param IsExtension If not null and the declaration is accepted as an

/// extension, the pointed variable is assigned true.

bool Sema::isAcceptableNestedNameSpecifier(const NamedDecl *SD,

                                           bool *IsExtension) {

  if (!SD)

    return false;

  SD = SD->getUnderlyingDecl();

  // Namespace and namespace aliases are fine.

  if (isa<NamespaceDecl>(SD))

    return true;

  if (!isa<TypeDecl>(SD))

    return false;

  // Determine whether we have a class (or, in C++11, an enum) or

  // a typedef thereof. If so, build the nested-name-specifier.

  QualType T = Context.getTypeDeclType(cast<TypeDecl>(SD));

  if (T->isDependentType())

    return true;

  if (const TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(SD)) {

    if (TD->getUnderlyingType()->isRecordType())

      return true;

    if (TD->getUnderlyingType()->isEnumeralType()) {

      if (Context.getLangOpts().CPlusPlus11)

        return true;

      if (IsExtension)

        *IsExtension = true;

    }

  } else if (isa<RecordDecl>(SD)) {

    return true;

  } else if (isa<EnumDecl>(SD)) {

    if (Context.getLangOpts().CPlusPlus11)

      return true;

    if (IsExtension)

      *IsExtension = true;

  }

  return false;

}

/// If the given nested-name-specifier begins with a bare identifier

/// (e.g., Base::), perform name lookup for that identifier as a

/// nested-name-specifier within the given scope, and return the result of that

/// name lookup.

NamedDecl *Sema::FindFirstQualifierInScope(Scope *S, NestedNameSpecifier *NNS) {

  if (!S || !NNS)

    return nullptr;

  while (NNS->getPrefix())

    NNS = NNS->getPrefix();

  if (NNS->getKind() != NestedNameSpecifier::Identifier)

    return nullptr;

  LookupResult Found(*this, NNS->getAsIdentifier(), SourceLocation(),

                     LookupNestedNameSpecifierName);

  LookupName(Found, S);

  assert(!Found.isAmbiguous() && "Cannot handle ambiguities here yet");

  if (!Found.isSingleResult())

    return nullptr;

  NamedDecl *Result = Found.getFoundDecl();

  if (isAcceptableNestedNameSpecifier(Result))

    return Result;

  return nullptr;

}

namespace {

// Callback to only accept typo corrections that can be a valid C++ member

// initializer: either a non-static field member or a base class.

class NestedNameSpecifierValidatorCCC final

    : public CorrectionCandidateCallback {

public:

  explicit NestedNameSpecifierValidatorCCC(Sema &SRef)

      : SRef(SRef) {}

  bool ValidateCandidate(const TypoCorrection &candidate) override {

    return SRef.isAcceptableNestedNameSpecifier(candidate.getCorrectionDecl());

  }

  std::unique_ptr<CorrectionCandidateCallback> clone() override {

    return std::make_unique<NestedNameSpecifierValidatorCCC>(*this);

  }

 private:

  Sema &SRef;

};

}

/// Build a new nested-name-specifier for "identifier::", as described

/// by ActOnCXXNestedNameSpecifier.

///

/// \param S Scope in which the nested-name-specifier occurs.

/// \param IdInfo Parser information about an identifier in the

///        nested-name-spec.

/// \param EnteringContext If true, enter the context specified by the

///        nested-name-specifier.

/// \param SS Optional nested name specifier preceding the identifier.

/// \param ScopeLookupResult Provides the result of name lookup within the

///        scope of the nested-name-specifier that was computed at template

///        definition time.

/// \param ErrorRecoveryLookup Specifies if the method is called to improve

///        error recovery and what kind of recovery is performed.

/// \param IsCorrectedToColon If not null, suggestion of replace '::' -> ':'

///        are allowed.  The bool value pointed by this parameter is set to

///       'true' if the identifier is treated as if it was followed by ':',

///        not '::'.

/// \param OnlyNamespace If true, only considers namespaces in lookup.

///

/// This routine differs only slightly from ActOnCXXNestedNameSpecifier, in

/// that it contains an extra parameter \p ScopeLookupResult, which provides

/// the result of name lookup within the scope of the nested-name-specifier

/// that was computed at template definition time.

///

/// If ErrorRecoveryLookup is true, then this call is used to improve error

/// recovery.  This means that it should not emit diagnostics, it should

/// just return true on failure.  It also means it should only return a valid

/// scope if it *knows* that the result is correct.  It should not return in a

/// dependent context, for example. Nor will it extend \p SS with the scope

/// specifier.

bool Sema::BuildCXXNestedNameSpecifier(Scope *S, NestedNameSpecInfo &IdInfo,

                                       bool EnteringContext, CXXScopeSpec &SS,

                                       NamedDecl *ScopeLookupResult,

                                       bool ErrorRecoveryLookup,

                                       bool *IsCorrectedToColon,

                                       bool OnlyNamespace) {

  if (IdInfo.Identifier->isEditorPlaceholder())

    return true;

  LookupResult Found(*this, IdInfo.Identifier, IdInfo.IdentifierLoc,

                     OnlyNamespace ? LookupNamespaceName

                                   : LookupNestedNameSpecifierName);

  QualType ObjectType = GetTypeFromParser(IdInfo.ObjectType);

  // Determine where to perform name lookup

  DeclContext *LookupCtx = nullptr;

  bool isDependent = false;

  if (IsCorrectedToColon)

    *IsCorrectedToColon = false;

  if (!ObjectType.isNull()) {

    // This nested-name-specifier occurs in a member access expression, e.g.,

    // x->B::f, and we are looking into the type of the object.

    assert(!SS.isSet() && "ObjectType and scope specifier cannot coexist");

    LookupCtx = computeDeclContext(ObjectType);

    isDependent = ObjectType->isDependentType();

  } else if (SS.isSet()) {

    // This nested-name-specifier occurs after another nested-name-specifier,

    // so look into the context associated with the prior nested-name-specifier.

    LookupCtx = computeDeclContext(SS, EnteringContext);

    isDependent = isDependentScopeSpecifier(SS);

    Found.setContextRange(SS.getRange());

  }

  bool ObjectTypeSearchedInScope = false;

  if (LookupCtx) {

    // Perform "qualified" name lookup into the declaration context we

    // computed, which is either the type of the base of a member access

    // expression or the declaration context associated with a prior

    // nested-name-specifier.

    // The declaration context must be complete.

    if (!LookupCtx->isDependentContext() &&

        RequireCompleteDeclContext(SS, LookupCtx))

      return true;

    LookupQualifiedName(Found, LookupCtx);

    if (!ObjectType.isNull() && Found.empty()) {

      // C++ [basic.lookup.classref]p4:

      //   If the id-expression in a class member access is a qualified-id of

      //   the form

      //

      //        class-name-or-namespace-name::...

      //

      //   the class-name-or-namespace-name following the . or -> operator is

      //   looked up both in the context of the entire postfix-expression and in

      //   the scope of the class of the object expression. If the name is found

      //   only in the scope of the class of the object expression, the name

      //   shall refer to a class-name. If the name is found only in the

      //   context of the entire postfix-expression, the name shall refer to a

      //   class-name or namespace-name. [...]

      //

      // Qualified name lookup into a class will not find a namespace-name,

      // so we do not need to diagnose that case specifically. However,

      // this qualified name lookup may find nothing. In that case, perform

      // unqualified name lookup in the given scope (if available) or

      // reconstruct the result from when name lookup was performed at template

      // definition time.

      if (S)

        LookupName(Found, S);

      else if (ScopeLookupResult)

        Found.addDecl(ScopeLookupResult);

      ObjectTypeSearchedInScope = true;

    }

  } else if (!isDependent) {

    // Perform unqualified name lookup in the current scope.

    LookupName(Found, S);

  }

  if (Found.isAmbiguous())

    return true;

  // If we performed lookup into a dependent context and did not find anything,

  // that's fine: just build a dependent nested-name-specifier.

  if (Found.empty() && isDependent &&

      !(LookupCtx && LookupCtx->isRecord() &&

        (!cast<CXXRecordDecl>(LookupCtx)->hasDefinition() ||

         !cast<CXXRecordDecl>(LookupCtx)->hasAnyDependentBases()))) {

    // Don't speculate if we're just trying to improve error recovery.

    if (ErrorRecoveryLookup)

      return true;

    // We were not able to compute the declaration context for a dependent

    // base object type or prior nested-name-specifier, so this

    // nested-name-specifier refers to an unknown specialization. Just build

    // a dependent nested-name-specifier.

    SS.Extend(Context, IdInfo.Identifier, IdInfo.IdentifierLoc, IdInfo.CCLoc);

    return false;

  }

  if (Found.empty() && !ErrorRecoveryLookup) {

    // If identifier is not found as class-name-or-namespace-name, but is found

    // as other entity, don't look for typos.

    LookupResult R(*this, Found.getLookupNameInfo(), LookupOrdinaryName);

    if (LookupCtx)

      LookupQualifiedName(R, LookupCtx);

    else if (S && !isDependent)

      LookupName(R, S);

    if (!R.empty()) {

      // Don't diagnose problems with this speculative lookup.

      R.suppressDiagnostics();

      // The identifier is found in ordinary lookup. If correction to colon is

      // allowed, suggest replacement to ':'.

      if (IsCorrectedToColon) {

        *IsCorrectedToColon = true;

        Diag(IdInfo.CCLoc, diag::err_nested_name_spec_is_not_class)

            << IdInfo.Identifier << getLangOpts().CPlusPlus

            << FixItHint::CreateReplacement(IdInfo.CCLoc, ":");

        if (NamedDecl *ND = R.getAsSingle<NamedDecl>())

          Diag(ND->getLocation(), diag::note_declared_at);

        return true;

      }

      // Replacement '::' -> ':' is not allowed, just issue respective error.

      Diag(R.getNameLoc(), OnlyNamespace

                               ? unsigned(diag::err_expected_namespace_name)

                               : unsigned(diag::err_expected_class_or_namespace))

          << IdInfo.Identifier << getLangOpts().CPlusPlus;

      if (NamedDecl *ND = R.getAsSingle<NamedDecl>())

        Diag(ND->getLocation(), diag::note_entity_declared_at)

            << IdInfo.Identifier;

      return true;

    }

  }

  if (Found.empty() && !ErrorRecoveryLookup && !getLangOpts().MSVCCompat) {

    // We haven't found anything, and we're not recovering from a

    // different kind of error, so look for typos.

    DeclarationName Name = Found.getLookupName();

    Found.clear();

    NestedNameSpecifierValidatorCCC CCC(*this);

    if (TypoCorrection Corrected = CorrectTypo(

            Found.getLookupNameInfo(), Found.getLookupKind(), S, &SS, CCC,

            CTK_ErrorRecovery, LookupCtx, EnteringContext)) {

      if (LookupCtx) {

        bool DroppedSpecifier =

            Corrected.WillReplaceSpecifier() &&

            Name.getAsString() == Corrected.getAsString(getLangOpts());

        if (DroppedSpecifier)

          SS.clear();

        diagnoseTypo(Corrected, PDiag(diag::err_no_member_suggest)

                                  << Name << LookupCtx << DroppedSpecifier

                                  << SS.getRange());

      } else

        diagnoseTypo(Corrected, PDiag(diag::err_undeclared_var_use_suggest)

                                  << Name);

      if (Corrected.getCorrectionSpecifier())

        SS.MakeTrivial(Context, Corrected.getCorrectionSpecifier(),

                       SourceRange(Found.getNameLoc()));

      if (NamedDecl *ND = Corrected.getFoundDecl())

        Found.addDecl(ND);

      Found.setLookupName(Corrected.getCorrection());

    } else {

      Found.setLookupName(IdInfo.Identifier);

    }

  }

  NamedDecl *SD =

      Found.isSingleResult() ? Found.getRepresentativeDecl() : nullptr;

  bool IsExtension = false;

  bool AcceptSpec = isAcceptableNestedNameSpecifier(SD, &IsExtension);

  if (!AcceptSpec && IsExtension) {

    AcceptSpec = true;

    Diag(IdInfo.IdentifierLoc, diag::ext_nested_name_spec_is_enum);

  }

  if (AcceptSpec) {

    if (!ObjectType.isNull() && !ObjectTypeSearchedInScope &&

        !getLangOpts().CPlusPlus11) {

      // C++03 [basic.lookup.classref]p4:

      //   [...] If the name is found in both contexts, the

      //   class-name-or-namespace-name shall refer to the same entity.

      //

      // We already found the name in the scope of the object. Now, look

      // into the current scope (the scope of the postfix-expression) to

      // see if we can find the same name there. As above, if there is no

      // scope, reconstruct the result from the template instantiation itself.

      //

      // Note that C++11 does *not* perform this redundant lookup.

      NamedDecl *OuterDecl;

      if (S) {

        LookupResult FoundOuter(*this, IdInfo.Identifier, IdInfo.IdentifierLoc,

                                LookupNestedNameSpecifierName);

        LookupName(FoundOuter, S);

        OuterDecl = FoundOuter.getAsSingle<NamedDecl>();

      } else

        OuterDecl = ScopeLookupResult;

      if (isAcceptableNestedNameSpecifier(OuterDecl) &&

          OuterDecl->getCanonicalDecl() != SD->getCanonicalDecl() &&

          (!isa<TypeDecl>(OuterDecl) || !isa<TypeDecl>(SD) ||

           !Context.hasSameType(

                            Context.getTypeDeclType(cast<TypeDecl>(OuterDecl)),

                               Context.getTypeDeclType(cast<TypeDecl>(SD))))) {

        if (ErrorRecoveryLookup)

          return true;

         Diag(IdInfo.IdentifierLoc,

              diag::err_nested_name_member_ref_lookup_ambiguous)

           << IdInfo.Identifier;

         Diag(SD->getLocation(), diag::note_ambig_member_ref_object_type)

           << ObjectType;

         Diag(OuterDecl->getLocation(), diag::note_ambig_member_ref_scope);

         // Fall through so that we'll pick the name we found in the object

         // type, since that's probably what the user wanted anyway.

       }

    }

    if (auto *TD = dyn_cast_or_null<TypedefNameDecl>(SD))

      MarkAnyDeclReferenced(TD->getLocation(), TD, /*OdrUse=*/false);

    // If we're just performing this lookup for error-recovery purposes,

    // don't extend the nested-name-specifier. Just return now.

    if (ErrorRecoveryLookup)

      return false;

    // The use of a nested name specifier may trigger deprecation warnings.

    DiagnoseUseOfDecl(SD, IdInfo.CCLoc);

    if (NamespaceDecl *Namespace = dyn_cast<NamespaceDecl>(SD)) {

      SS.Extend(Context, Namespace, IdInfo.IdentifierLoc, IdInfo.CCLoc);

      return false;

    }

    if (NamespaceAliasDecl *Alias = dyn_cast<NamespaceAliasDecl>(SD)) {

      SS.Extend(Context, Alias, IdInfo.IdentifierLoc, IdInfo.CCLoc);

      return false;

    }

    QualType T =

        Context.getTypeDeclType(cast<TypeDecl>(SD->getUnderlyingDecl()));

    if (T->isEnumeralType())

      Diag(IdInfo.IdentifierLoc, diag::warn_cxx98_compat_enum_nested_name_spec);

    TypeLocBuilder TLB;

    if (const auto *USD = dyn_cast<UsingShadowDecl>(SD)) {

      T = Context.getUsingType(USD, T);

      TLB.pushTypeSpec(T).setNameLoc(IdInfo.IdentifierLoc);

    } else if (isa<InjectedClassNameType>(T)) {

      InjectedClassNameTypeLoc InjectedTL

        = TLB.push<InjectedClassNameTypeLoc>(T);

      InjectedTL.setNameLoc(IdInfo.IdentifierLoc);

    } else if (isa<RecordType>(T)) {

      RecordTypeLoc RecordTL = TLB.push<RecordTypeLoc>(T);

      RecordTL.setNameLoc(IdInfo.IdentifierLoc);

    } else if (isa<TypedefType>(T)) {

      TypedefTypeLoc TypedefTL = TLB.push<TypedefTypeLoc>(T);

      TypedefTL.setNameLoc(IdInfo.IdentifierLoc);

    } else if (isa<EnumType>(T)) {

      EnumTypeLoc EnumTL = TLB.push<EnumTypeLoc>(T);

      EnumTL.setNameLoc(IdInfo.IdentifierLoc);

    } else if (isa<TemplateTypeParmType>(T)) {

      TemplateTypeParmTypeLoc TemplateTypeTL

        = TLB.push<TemplateTypeParmTypeLoc>(T);

      TemplateTypeTL.setNameLoc(IdInfo.IdentifierLoc);

    } else if (isa<UnresolvedUsingType>(T)) {

      UnresolvedUsingTypeLoc UnresolvedTL

        = TLB.push<UnresolvedUsingTypeLoc>(T);

      UnresolvedTL.setNameLoc(IdInfo.IdentifierLoc);

    } else if (isa<SubstTemplateTypeParmType>(T)) {

      SubstTemplateTypeParmTypeLoc TL

        = TLB.push<SubstTemplateTypeParmTypeLoc>(T);

      TL.setNameLoc(IdInfo.IdentifierLoc);

    } else if (isa<SubstTemplateTypeParmPackType>(T)) {

      SubstTemplateTypeParmPackTypeLoc TL

        = TLB.push<SubstTemplateTypeParmPackTypeLoc>(T);

      TL.setNameLoc(IdInfo.IdentifierLoc);

    } else {

      llvm_unreachable("Unhandled TypeDecl node in nested-name-specifier");

    }

    SS.Extend(Context, SourceLocation(), TLB.getTypeLocInContext(Context, T),

              IdInfo.CCLoc);

    return false;

  }

  // Otherwise, we have an error case.  If we don't want diagnostics, just

  // return an error now.

  if (ErrorRecoveryLookup)

    return true;

  // If we didn't find anything during our lookup, try again with

  // ordinary name lookup, which can help us produce better error

  // messages.

  if (Found.empty()) {

    Found.clear(LookupOrdinaryName);

    LookupName(Found, S);

  }

  // In Microsoft mode, if we are within a templated function and we can't

  // resolve Identifier, then extend the SS with Identifier. This will have

  // the effect of resolving Identifier during template instantiation.

  // The goal is to be able to resolve a function call whose

  // nested-name-specifier is located inside a dependent base class.

  // Example:

  //

  // class C {

  // public:

  //    static void foo2() {  }

  // };

  // template <class T> class A { public: typedef C D; };

  //

  // template <class T> class B : public A<T> {

  // public:

  //   void foo() { D::foo2(); }

  // };

  if (getLangOpts().MSVCCompat) {

    DeclContext *DC = LookupCtx ? LookupCtx : CurContext;

    if (DC->isDependentContext() && DC->isFunctionOrMethod()) {

      CXXRecordDecl *ContainingClass = dyn_cast<CXXRecordDecl>(DC->getParent());

      if (ContainingClass && ContainingClass->hasAnyDependentBases()) {

        Diag(IdInfo.IdentifierLoc,

             diag::ext_undeclared_unqual_id_with_dependent_base)

            << IdInfo.Identifier << ContainingClass;

        SS.Extend(Context, IdInfo.Identifier, IdInfo.IdentifierLoc,

                  IdInfo.CCLoc);

        return false;

      }

    }

  }

  if (!Found.empty()) {

    if (TypeDecl *TD = Found.getAsSingle<TypeDecl>()) {

      Diag(IdInfo.IdentifierLoc, diag::err_expected_class_or_namespace)

          << Context.getTypeDeclType(TD) << getLangOpts().CPlusPlus;

    } else if (Found.getAsSingle<TemplateDecl>()) {

      ParsedType SuggestedType;

      DiagnoseUnknownTypeName(IdInfo.Identifier, IdInfo.IdentifierLoc, S, &SS,

                              SuggestedType);

    } else {

      Diag(IdInfo.IdentifierLoc, diag::err_expected_class_or_namespace)

          << IdInfo.Identifier << getLangOpts().CPlusPlus;

      if (NamedDecl *ND = Found.getAsSingle<NamedDecl>())

        Diag(ND->getLocation(), diag::note_entity_declared_at)

            << IdInfo.Identifier;

    }

  } else if (SS.isSet())

    Diag(IdInfo.IdentifierLoc, diag::err_no_member) << IdInfo.Identifier

        << LookupCtx << SS.getRange();

  else

    Diag(IdInfo.IdentifierLoc, diag::err_undeclared_var_use)

        << IdInfo.Identifier;

  return true;

}

bool Sema::ActOnCXXNestedNameSpecifier(Scope *S, NestedNameSpecInfo &IdInfo,

                                       bool EnteringContext, CXXScopeSpec &SS,

                                       bool *IsCorrectedToColon,

                                       bool OnlyNamespace) {

  if (SS.isInvalid())

    return true;

  return BuildCXXNestedNameSpecifier(S, IdInfo, EnteringContext, SS,

                                     /*ScopeLookupResult=*/nullptr, false,

                                     IsCorrectedToColon, OnlyNamespace);

}

bool Sema::ActOnCXXNestedNameSpecifierDecltype(CXXScopeSpec &SS,

                                               const DeclSpec &DS,

                                               SourceLocation ColonColonLoc) {

  if (SS.isInvalid() || DS.getTypeSpecType() == DeclSpec::TST_error)

    return true;

  assert(DS.getTypeSpecType() == DeclSpec::TST_decltype);

  QualType T = BuildDecltypeType(DS.getRepAsExpr());

  if (T.isNull())

    return true;

  if (!T->isDependentType() && !T->getAs<TagType>()) {

    Diag(DS.getTypeSpecTypeLoc(), diag::err_expected_class_or_namespace)

      << T << getLangOpts().CPlusPlus;

    return true;

  }

  TypeLocBuilder TLB;

  DecltypeTypeLoc DecltypeTL = TLB.push<DecltypeTypeLoc>(T);

  DecltypeTL.setDecltypeLoc(DS.getTypeSpecTypeLoc());

  DecltypeTL.setRParenLoc(DS.getTypeofParensRange().getEnd());

  SS.Extend(Context, SourceLocation(), TLB.getTypeLocInContext(Context, T),

            ColonColonLoc);

  return false;

}

/// IsInvalidUnlessNestedName - This method is used for error recovery

/// purposes to determine whether the specified identifier is only valid as

/// a nested name specifier, for example a namespace name.  It is

/// conservatively correct to always return false from this method.

///

/// The arguments are the same as those passed to ActOnCXXNestedNameSpecifier.

bool Sema::IsInvalidUnlessNestedName(Scope *S, CXXScopeSpec &SS,

                                     NestedNameSpecInfo &IdInfo,

                                     bool EnteringContext) {

  if (SS.isInvalid())

    return false;

  return !BuildCXXNestedNameSpecifier(S, IdInfo, EnteringContext, SS,

                                      /*ScopeLookupResult=*/nullptr, true);

}

bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,

                                       CXXScopeSpec &SS,

                                       SourceLocation TemplateKWLoc,

                                       TemplateTy OpaqueTemplate,

                                       SourceLocation TemplateNameLoc,

                                       SourceLocation LAngleLoc,

                                       ASTTemplateArgsPtr TemplateArgsIn,

                                       SourceLocation RAngleLoc,

                                       SourceLocation CCLoc,

                                       bool EnteringContext) {

  if (SS.isInvalid())

    return true;

  TemplateName Template = OpaqueTemplate.get();

  // Translate the parser's template argument list in our AST format.

  TemplateArgumentListInfo TemplateArgs(LAngleLoc, RAngleLoc);

  translateTemplateArguments(TemplateArgsIn, TemplateArgs);

  DependentTemplateName *DTN = Template.getAsDependentTemplateName();

  if (DTN && DTN->isIdentifier()) {

    // Handle a dependent template specialization for which we cannot resolve

    // the template name.

    assert(DTN->getQualifier() == SS.getScopeRep());

    QualType T = Context.getDependentTemplateSpecializationType(

        ElaboratedTypeKeyword::None, DTN->getQualifier(), DTN->getIdentifier(),

        TemplateArgs.arguments());

    // Create source-location information for this type.

    TypeLocBuilder Builder;

    DependentTemplateSpecializationTypeLoc SpecTL

      = Builder.push<DependentTemplateSpecializationTypeLoc>(T);

    SpecTL.setElaboratedKeywordLoc(SourceLocation());

    SpecTL.setQualifierLoc(SS.getWithLocInContext(Context));