diff --git a/clang/include/clang/Tooling/Syntax/BuildTree.h b/clang/include/clang/Tooling/Syntax/BuildTree.h
--- a/clang/include/clang/Tooling/Syntax/BuildTree.h
+++ b/clang/include/clang/Tooling/Syntax/BuildTree.h
@@ -39,7 +39,7 @@
 /// Returns it as a pointer to the base class `Tree`.
 syntax::Tree *
 createTree(syntax::Arena &A,
-           std::vector<std::pair<syntax::Node *, syntax::NodeRole>> Children,
+           ArrayRef<std::pair<syntax::Node *, syntax::NodeRole>> Children,
            syntax::NodeKind K);
 
 // Synthesis of Syntax Nodes
diff --git a/clang/lib/Tooling/Syntax/Synthesis.cpp b/clang/lib/Tooling/Syntax/Synthesis.cpp
--- a/clang/lib/Tooling/Syntax/Synthesis.cpp
+++ b/clang/lib/Tooling/Syntax/Synthesis.cpp
@@ -190,7 +190,7 @@
 
 syntax::Tree *clang::syntax::createTree(
     syntax::Arena &A,
-    std::vector<std::pair<syntax::Node *, syntax::NodeRole>> Children,
+    ArrayRef<std::pair<syntax::Node *, syntax::NodeRole>> Children,
     syntax::NodeKind K) {
   auto *T = allocateTree(A, K);
   FactoryImpl::setCanModify(T);