1 files changed, 26 insertions, 7 deletions
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 4dccf2f459c..263bc3104ef 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -4280,19 +4280,26 @@ Sema::TemplateDeductionResult Sema::DeduceTemplateArguments(
 }
 
 namespace {
+  struct DependentAuto { bool IsPack; };
 
   /// Substitute the 'auto' specifier or deduced template specialization type
   /// specifier within a type for a given replacement type.
   class SubstituteDeducedTypeTransform :
       public TreeTransform<SubstituteDeducedTypeTransform> {
     QualType Replacement;
+    bool ReplacementIsPack;
     bool UseTypeSugar;
 
   public:
+    SubstituteDeducedTypeTransform(Sema &SemaRef, DependentAuto DA)
+        : TreeTransform<SubstituteDeducedTypeTransform>(SemaRef), Replacement(),
+          ReplacementIsPack(DA.IsPack), UseTypeSugar(true) {}
+
     SubstituteDeducedTypeTransform(Sema &SemaRef, QualType Replacement,
-                            bool UseTypeSugar = true)
+                                   bool UseTypeSugar = true)
         : TreeTransform<SubstituteDeducedTypeTransform>(SemaRef),
-          Replacement(Replacement), UseTypeSugar(UseTypeSugar) {}
+          Replacement(Replacement), ReplacementIsPack(false),
+          UseTypeSugar(UseTypeSugar) {}
 
     QualType TransformDesugared(TypeLocBuilder &TLB, DeducedTypeLoc TL) {
       assert(isa<TemplateTypeParmType>(Replacement) &&
@@ -4317,7 +4324,8 @@ namespace {
         return TransformDesugared(TLB, TL);
 
       QualType Result = SemaRef.Context.getAutoType(
-          Replacement, TL.getTypePtr()->getKeyword(), Replacement.isNull());
+          Replacement, TL.getTypePtr()->getKeyword(), Replacement.isNull(),
+          ReplacementIsPack);
       auto NewTL = TLB.push<AutoTypeLoc>(Result);
       NewTL.setNameLoc(TL.getNameLoc());
       return Result;
@@ -4408,9 +4416,12 @@ Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result,
     Init = NonPlaceholder.get();
   }
 
+  DependentAuto DependentResult = {
+      /*.IsPack = */ (bool)Type.getAs<PackExpansionTypeLoc>()};
+
   if (!DependentDeductionDepth &&
       (Type.getType()->isDependentType() || Init->isTypeDependent())) {
-    Result = SubstituteDeducedTypeTransform(*this, QualType()).Apply(Type);
+    Result = SubstituteDeducedTypeTransform(*this, DependentResult).Apply(Type);
     assert(!Result.isNull() && "substituting DependentTy can't fail");
     return DAR_Succeeded;
   }
@@ -4478,7 +4489,8 @@ Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result,
   auto DeductionFailed = [&](TemplateDeductionResult TDK,
                              ArrayRef<SourceRange> Ranges) -> DeduceAutoResult {
     if (Init->isTypeDependent()) {
-      Result = SubstituteDeducedTypeTransform(*this, QualType()).Apply(Type);
+      Result =
+          SubstituteDeducedTypeTransform(*this, DependentResult).Apply(Type);
       assert(!Result.isNull() && "substituting DependentTy can't fail");
       return DAR_Succeeded;
     }
@@ -4559,7 +4571,10 @@ Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result,
 QualType Sema::SubstAutoType(QualType TypeWithAuto,
                              QualType TypeToReplaceAuto) {
   if (TypeToReplaceAuto->isDependentType())
-    TypeToReplaceAuto = QualType();
+    return SubstituteDeducedTypeTransform(
+               *this, DependentAuto{
+                          TypeToReplaceAuto->containsUnexpandedParameterPack()})
+        .TransformType(TypeWithAuto);
   return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
       .TransformType(TypeWithAuto);
 }
@@ -4567,7 +4582,11 @@ QualType Sema::SubstAutoType(QualType TypeWithAuto,
 TypeSourceInfo *Sema::SubstAutoTypeSourceInfo(TypeSourceInfo *TypeWithAuto,
                                               QualType TypeToReplaceAuto) {
   if (TypeToReplaceAuto->isDependentType())
-    TypeToReplaceAuto = QualType();
+    return SubstituteDeducedTypeTransform(
+               *this,
+               DependentAuto{
+                   TypeToReplaceAuto->containsUnexpandedParameterPack()})
+        .TransformType(TypeWithAuto);
   return SubstituteDeducedTypeTransform(*this, TypeToReplaceAuto)
       .TransformType(TypeWithAuto);
 }