3 files changed, 62 insertions, 0 deletions
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 54acca7dc62..9477e414cf5 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -44,6 +44,7 @@
 #include "clang/AST/TypeLoc.h"
 #include "clang/AST/TypeVisitor.h"
 #include "clang/AST/UnresolvedSet.h"
+#include "clang/Basic/Builtins.h"
 #include "clang/Basic/ExceptionSpecificationType.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/IdentifierTable.h"
@@ -483,6 +484,7 @@ namespace clang {
     ExpectedDecl VisitUsingDirectiveDecl(UsingDirectiveDecl *D);
     ExpectedDecl VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D);
     ExpectedDecl VisitUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D);
+    ExpectedDecl VisitBuiltinTemplateDecl(BuiltinTemplateDecl *D);
 
     Expected<ObjCTypeParamList *>
     ImportObjCTypeParamList(ObjCTypeParamList *list);
@@ -4464,6 +4466,20 @@ ExpectedDecl ASTNodeImporter::VisitUnresolvedUsingTypenameDecl(
   return ToUsing;
 }
 
+ExpectedDecl ASTNodeImporter::VisitBuiltinTemplateDecl(BuiltinTemplateDecl *D) {
+  Decl* ToD = nullptr;
+  switch (D->getBuiltinTemplateKind()) {
+  case BuiltinTemplateKind::BTK__make_integer_seq:
+    ToD = Importer.getToContext().getMakeIntegerSeqDecl();
+    break;
+  case BuiltinTemplateKind::BTK__type_pack_element:
+    ToD = Importer.getToContext().getTypePackElementDecl();
+    break;
+  }
+  assert(ToD && "BuiltinTemplateDecl of unsupported kind!");
+  Importer.MapImported(D, ToD);
+  return ToD;
+}
 
 Error ASTNodeImporter::ImportDefinition(
     ObjCInterfaceDecl *From, ObjCInterfaceDecl *To, ImportDefinitionKind Kind) {
diff --git a/clang/test/Import/builtin-template/Inputs/S.cpp b/clang/test/Import/builtin-template/Inputs/S.cpp
new file mode 100644
index 00000000000..d5c9a9ae030
--- /dev/null
+++ b/clang/test/Import/builtin-template/Inputs/S.cpp
@@ -0,0 +1,16 @@
+template <class T, T... I>
+struct Seq {
+  static constexpr T PackSize = sizeof...(I);
+};
+
+template <typename T, T N>
+using MakeSeq = __make_integer_seq<Seq, T, N>;
+
+
+using SizeT = decltype(sizeof(int));
+
+template <SizeT i, typename ...T>
+using TypePackElement = __type_pack_element<i, T...>;
+
+template <int i>
+struct X;
diff --git a/clang/test/Import/builtin-template/test.cpp b/clang/test/Import/builtin-template/test.cpp
new file mode 100644
index 00000000000..3ae7b53e9d4
--- /dev/null
+++ b/clang/test/Import/builtin-template/test.cpp
@@ -0,0 +1,30 @@
+// RUN: clang-import-test -dump-ast -import %S/Inputs/S.cpp -expression %s -Xcc -DSEQ | FileCheck --check-prefix=CHECK-SEQ %s
+// RUN: clang-import-test -dump-ast -import %S/Inputs/S.cpp -expression %s -Xcc -DPACK | FileCheck --check-prefix=CHECK-PACK %s
+// RUN: clang-import-test -dump-ast -import %S/Inputs/S.cpp -expression %s -Xcc -DPACK -Xcc -DSEQ | FileCheck --check-prefixes=CHECK-SEQ,CHECK-PACK %s
+
+// CHECK-SEQ: BuiltinTemplateDecl
+// CHECK-SEQ-SAME: <invalid sloc>
+// CHECK-SEQ-SAME: implicit
+// CHECK-SEQ-SAME: __make_integer_seq
+
+// CHECK-PACK: BuiltinTemplateDecl
+// CHECK-PACK-SAME: <invalid sloc>
+// CHECK-PACK-SAME: implicit
+// CHECK-PACK-SAME: __type_pack_element
+
+void expr() {
+#ifdef SEQ
+  typedef MakeSeq<int, 3> M1;
+  M1 m1;
+  typedef MakeSeq<long, 4> M2;
+  M2 m2;
+  static_assert(M1::PackSize == 3, "");
+  static_assert(M2::PackSize == 4, "");
+#endif
+
+#ifdef PACK
+  static_assert(__is_same(TypePackElement<0, X<0>>, X<0>), "");
+  static_assert(__is_same(TypePackElement<0, X<0>, X<1>>, X<0>), "");
+  static_assert(__is_same(TypePackElement<1, X<0>, X<1>>, X<1>), "");
+#endif
+}