From 077bd1afd180ede4aa4990a69ae0bb8ebf2bb9aa Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Mon, 8 Oct 2018 10:00:15 -0700
Subject: [PATCH] Add regression test

---
 .../compiler/discriminantPropertyCheck.ts     | 34 ++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/tests/cases/compiler/discriminantPropertyCheck.ts b/tests/cases/compiler/discriminantPropertyCheck.ts
index e493f6bf770..16fb847bdf0 100644
--- a/tests/cases/compiler/discriminantPropertyCheck.ts
+++ b/tests/cases/compiler/discriminantPropertyCheck.ts
@@ -66,4 +66,36 @@ function foo6(x: Item) {
     if (x.foo !== undefined && x.qux) {
         x.foo.length;  // Error, intervening discriminant guard
     }
-}
\ No newline at end of file
+}
+
+// Repro from #27493
+
+enum Types { Str = 1, Num = 2 }
+
+type Instance = StrType | NumType;
+
+interface StrType {
+    type: Types.Str;
+    value: string;
+    length: number;
+}
+
+interface NumType {
+    type: Types.Num;
+    value: number;
+}
+
+function func2(inst: Instance) {
+    while (true) {
+        switch (inst.type) {
+            case Types.Str: {
+                inst.value.length;
+                break;
+            }
+            case Types.Num: {
+                inst.value.toExponential;
+                break;
+            }
+        }
+    }
+}