From 74c57caa900e0439cfd46fec587c0c2ff87d8f0e Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Wed, 22 Aug 2018 07:16:31 -0700
Subject: [PATCH] Add regression test

---
 .../conformance/types/mapped/mappedTypesArraysTuples.ts   | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tests/cases/conformance/types/mapped/mappedTypesArraysTuples.ts b/tests/cases/conformance/types/mapped/mappedTypesArraysTuples.ts
index c936a86c89..5d8fbc4b37 100644
--- a/tests/cases/conformance/types/mapped/mappedTypesArraysTuples.ts
+++ b/tests/cases/conformance/types/mapped/mappedTypesArraysTuples.ts
@@ -85,3 +85,11 @@ declare function mapArray<T extends any[]>(arr: T): Mapped<T>;
 function acceptMappedArray<T extends any[]>(arr: T) {
     acceptArray(mapArray(arr));
 }
+
+// Repro from #26163
+
+type Unconstrained<T> = ElementType<Mapped<T>>;
+type T1 = Unconstrained<[string, number, boolean]>;  // string | number | boolean
+
+type Constrained<T extends any[]> = ElementType<Mapped<T>>;
+type T2 = Constrained<[string, number, boolean]>;  // string | number | boolean