From c6a670d26cddfe97790e2f3c2d4c1670860b2b2f Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Fri, 17 May 2019 15:59:01 -0700
Subject: [PATCH] Add regression test

---
 .../conformance/types/keyof/keyofAndIndexedAccess2.ts    | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tests/cases/conformance/types/keyof/keyofAndIndexedAccess2.ts b/tests/cases/conformance/types/keyof/keyofAndIndexedAccess2.ts
index 5251a83bb0611..a99c2b0a7a106 100644
--- a/tests/cases/conformance/types/keyof/keyofAndIndexedAccess2.ts
+++ b/tests/cases/conformance/types/keyof/keyofAndIndexedAccess2.ts
@@ -138,3 +138,12 @@ function fn4<K extends number>() {
     let x: Array<string>[K] = 'abc';
     let y: ReadonlyArray<string>[K] = 'abc';
 }
+
+// Repro from #31439
+
+export class c {
+  [x: string]: string;
+  constructor() {
+    this["a"] = "b";
+  }
+}