1 files changed, 5 insertions, 1 deletions
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index c0bc34fa975..925860a6000 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -764,6 +764,9 @@ public:
   ///
   /// By default, builds a new AutoType with the given deduced type.
   QualType RebuildAutoType(QualType Deduced, bool IsDecltypeAuto) {
+    // Note, IsDependent is always false here: we implicitly convert an 'auto'
+    // which has been deduced to a dependent type into an undeduced 'auto', so
+    // that we'll retry deduction after the transformation.
     return SemaRef.Context.getAutoType(Deduced, IsDecltypeAuto);
   }
 
@@ -4500,7 +4503,8 @@ QualType TreeTransform<Derived>::TransformAutoType(TypeLocBuilder &TLB,
   }
 
   QualType Result = TL.getType();
-  if (getDerived().AlwaysRebuild() || NewDeduced != OldDeduced) {
+  if (getDerived().AlwaysRebuild() || NewDeduced != OldDeduced ||
+      T->isDependentType()) {
     Result = getDerived().RebuildAutoType(NewDeduced, T->isDecltypeAuto());
     if (Result.isNull())
       return QualType();