1 files changed, 52 insertions, 22 deletions

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index ac643af1490..21bdd945f06 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -8533,12 +8533,18 @@ void Sema::PushUsingDirective(Scope *S, UsingDirectiveDecl *UDir) {
 Decl *Sema::ActOnUsingDeclaration(Scope *S,
                                   AccessSpecifier AS,
                                   SourceLocation UsingLoc,
+                                  SourceLocation TypenameLoc,
                                   CXXScopeSpec &SS,
                                   UnqualifiedId &Name,
-                                  AttributeList *AttrList,
-                                  SourceLocation TypenameLoc) {
+                                  SourceLocation EllipsisLoc,
+                                  AttributeList *AttrList) {
   assert(S->getFlags() & Scope::DeclScope && "Invalid Scope.");
 
+  if (SS.isEmpty()) {
+    Diag(Name.getLocStart(), diag::err_using_requires_qualname);
+    return nullptr;
+  }
+
   switch (Name.getKind()) {
   case UnqualifiedId::IK_ImplicitSelfParam:
   case UnqualifiedId::IK_Identifier:
@@ -8584,14 +8590,23 @@ Decl *Sema::ActOnUsingDeclaration(Scope *S,
       << FixItHint::CreateInsertion(SS.getRange().getBegin(), "using ");
   }
 
-  if (DiagnoseUnexpandedParameterPack(SS, UPPC_UsingDeclaration) ||
-      DiagnoseUnexpandedParameterPack(TargetNameInfo, UPPC_UsingDeclaration))
-    return nullptr;
+  if (EllipsisLoc.isInvalid()) {
+    if (DiagnoseUnexpandedParameterPack(SS, UPPC_UsingDeclaration) ||
+        DiagnoseUnexpandedParameterPack(TargetNameInfo, UPPC_UsingDeclaration))
+      return nullptr;
+  } else {
+    if (!SS.getScopeRep()->containsUnexpandedParameterPack() &&
+        !TargetNameInfo.containsUnexpandedParameterPack()) {
+      Diag(EllipsisLoc, diag::err_pack_expansion_without_parameter_packs)
+        << SourceRange(SS.getBeginLoc(), TargetNameInfo.getEndLoc());
+      EllipsisLoc = SourceLocation();
+    }
+  }
 
-  NamedDecl *UD = BuildUsingDeclaration(S, AS, UsingLoc, SS,
-                                        TargetNameInfo, AttrList,
-                                        /* IsInstantiation */ false,
-                                        TypenameLoc.isValid(), TypenameLoc);
+  NamedDecl *UD =
+      BuildUsingDeclaration(S, AS, UsingLoc, TypenameLoc.isValid(), TypenameLoc,
+                            SS, TargetNameInfo, EllipsisLoc, AttrList,
+                            /*IsInstantiation*/false);
   if (UD)
     PushOnScopeChains(UD, S, /*AddToContext*/ false);
 
@@ -8654,6 +8669,7 @@ bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
              diag::err_using_decl_nested_name_specifier_is_current_class)
           << Using->getQualifierLoc().getSourceRange();
         Diag(Orig->getLocation(), diag::note_using_decl_target);
+        Using->setInvalidDecl();
         return true;
       }
 
@@ -8663,6 +8679,7 @@ bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
         << cast<CXXRecordDecl>(CurContext)
         << Using->getQualifierLoc().getSourceRange();
       Diag(Orig->getLocation(), diag::note_using_decl_target);
+      Using->setInvalidDecl();
       return true;
     }
   }
@@ -8686,7 +8703,7 @@ bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
     // We can have UsingDecls in our Previous results because we use the same
     // LookupResult for checking whether the UsingDecl itself is a valid
     // redeclaration.
-    if (isa<UsingDecl>(D))
+    if (isa<UsingDecl>(D) || isa<UsingPackDecl>(D))
       continue;
 
     if (IsEquivalentForUsingDecl(Context, D, Target)) {
@@ -8732,6 +8749,7 @@ bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
 
     Diag(Target->getLocation(), diag::note_using_decl_target);
     Diag(OldDecl->getLocation(), diag::note_using_decl_conflict);
+    Using->setInvalidDecl();
     return true;
   }
 
@@ -8744,6 +8762,7 @@ bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
     Diag(Using->getLocation(), diag::err_using_decl_conflict);
     Diag(Target->getLocation(), diag::note_using_decl_target);
     Diag(Tag->getLocation(), diag::note_using_decl_conflict);
+    Using->setInvalidDecl();
     return true;
   }
 
@@ -8753,6 +8772,7 @@ bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
   Diag(Using->getLocation(), diag::err_using_decl_conflict);
   Diag(Target->getLocation(), diag::note_using_decl_target);
   Diag(NonTag->getLocation(), diag::note_using_decl_conflict);
+  Using->setInvalidDecl();
   return true;
 }
 
@@ -8960,23 +8980,19 @@ private:
 ///   the lookup differently for these declarations.
 NamedDecl *Sema::BuildUsingDeclaration(Scope *S, AccessSpecifier AS,
                                        SourceLocation UsingLoc,
+                                       bool HasTypenameKeyword,
+                                       SourceLocation TypenameLoc,
                                        CXXScopeSpec &SS,
                                        DeclarationNameInfo NameInfo,
+                                       SourceLocation EllipsisLoc,
                                        AttributeList *AttrList,
-                                       bool IsInstantiation,
-                                       bool HasTypenameKeyword,
-                                       SourceLocation TypenameLoc) {
+                                       bool IsInstantiation) {
   assert(!SS.isInvalid() && "Invalid CXXScopeSpec.");
   SourceLocation IdentLoc = NameInfo.getLoc();
   assert(IdentLoc.isValid() && "Invalid TargetName location.");
 
   // FIXME: We ignore attributes for now.
 
-  if (SS.isEmpty()) {
-    Diag(IdentLoc, diag::err_using_requires_qualname);
-    return nullptr;
-  }
-
   // For an inheriting constructor declaration, the name of the using
   // declaration is the name of a constructor in this class, not in the
   // base class.
@@ -9042,16 +9058,17 @@ NamedDecl *Sema::BuildUsingDeclaration(Scope *S, AccessSpecifier AS,
   DeclContext *LookupContext = computeDeclContext(SS);
   NamedDecl *D;
   NestedNameSpecifierLoc QualifierLoc = SS.getWithLocInContext(Context);
-  if (!LookupContext) {
+  if (!LookupContext || EllipsisLoc.isValid()) {
     if (HasTypenameKeyword) {
       // FIXME: not all declaration name kinds are legal here
       D = UnresolvedUsingTypenameDecl::Create(Context, CurContext,
                                               UsingLoc, TypenameLoc,
                                               QualifierLoc,
-                                              IdentLoc, NameInfo.getName());
+                                              IdentLoc, NameInfo.getName(),
+                                              EllipsisLoc);
     } else {
       D = UnresolvedUsingValueDecl::Create(Context, CurContext, UsingLoc, 
-                                           QualifierLoc, NameInfo);
+                                           QualifierLoc, NameInfo, EllipsisLoc);
     }
     D->setAccess(AS);
     CurContext->addDecl(D);
@@ -9211,6 +9228,19 @@ NamedDecl *Sema::BuildUsingDeclaration(Scope *S, AccessSpecifier AS,
   return UD;
 }
 
+NamedDecl *Sema::BuildUsingPackDecl(NamedDecl *InstantiatedFrom,
+                                    ArrayRef<NamedDecl *> Expansions) {
+  assert(isa<UnresolvedUsingValueDecl>(InstantiatedFrom) ||
+         isa<UnresolvedUsingTypenameDecl>(InstantiatedFrom) ||
+         isa<UsingPackDecl>(InstantiatedFrom));
+
+  auto *UPD =
+      UsingPackDecl::Create(Context, CurContext, InstantiatedFrom, Expansions);
+  UPD->setAccess(InstantiatedFrom->getAccess());
+  CurContext->addDecl(UPD);
+  return UPD;
+}
+
 /// Additional checks for a using declaration referring to a constructor name.
 bool Sema::CheckInheritingConstructorUsingDecl(UsingDecl *UD) {
   assert(!UD->hasTypename() && "expecting a constructor name");
@@ -9264,7 +9294,7 @@ bool Sema::CheckUsingDeclRedeclaration(SourceLocation UsingLoc,
     // scope?
     if (Qual->isDependent() && !HasTypenameKeyword) {
       for (auto *D : Prev) {
-        if (!isa<TypeDecl>(D) && !isa<UsingDecl>(D)) {
+        if (!isa<TypeDecl>(D) && !isa<UsingDecl>(D) && !isa<UsingPackDecl>(D)) {
           bool OldCouldBeEnumerator =
               isa<UnresolvedUsingValueDecl>(D) || isa<EnumConstantDecl>(D);
           Diag(NameLoc,