From 7862e58354888d5ccf9c378ac74863d5febabc21 Mon Sep 17 00:00:00 2001
From: Andrew Casey <andrew.casey@microsoft.com>
Date: Mon, 21 Oct 2019 17:41:06 -0700
Subject: [PATCH] Handle undefined from getPropertyNameForPropertyNameNode

...which can be returned when the property name is computed.

Part of #34404
---
 src/services/navigationBar.ts                 |  3 +-
 .../navigationBarComputedPropertyName.ts      | 57 +++++++++++++++++++
 2 files changed, 59 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/navigationBarComputedPropertyName.ts

diff --git a/src/services/navigationBar.ts b/src/services/navigationBar.ts
index 03b9d6216c874..49310ef827f1e 100644
--- a/src/services/navigationBar.ts
+++ b/src/services/navigationBar.ts
@@ -648,7 +648,8 @@ namespace ts.NavigationBar {
 
         const declName = getNameOfDeclaration(<Declaration>node);
         if (declName && isPropertyName(declName)) {
-            return unescapeLeadingUnderscores(getPropertyNameForPropertyNameNode(declName)!); // TODO: GH#18217
+            const propertyName = getPropertyNameForPropertyNameNode(declName);
+            return propertyName && unescapeLeadingUnderscores(propertyName);
         }
         switch (node.kind) {
             case SyntaxKind.FunctionExpression:
diff --git a/tests/cases/fourslash/navigationBarComputedPropertyName.ts b/tests/cases/fourslash/navigationBarComputedPropertyName.ts
new file mode 100644
index 0000000000000..fc6fb808f74fe
--- /dev/null
+++ b/tests/cases/fourslash/navigationBarComputedPropertyName.ts
@@ -0,0 +1,57 @@
+/// <reference path="fourslash.ts"/>
+
+////function F(key, value) {
+////    return {
+////        [key]: value,
+////        "prop": true
+////    }
+////}
+
+verify.navigationTree({
+    "text": "<global>",
+    "kind": "script",
+    "childItems": [
+        {
+            "text": "F",
+            "kind": "function",
+            "childItems": [
+                {
+                    "text": "[key]",
+                    "kind": "property"
+                },
+                {
+                    "text": "\"prop\"",
+                    "kind": "property"
+                }
+            ]
+        }
+    ]
+});
+
+verify.navigationBar([
+    {
+        "text": "<global>",
+        "kind": "script",
+        "childItems": [
+            {
+                "text": "F",
+                "kind": "function"
+            }
+        ]
+    },
+    {
+        "text": "F",
+        "kind": "function",
+        "childItems": [
+            {
+                "text": "[key]",
+                "kind": "property"
+            },
+            {
+                "text": "\"prop\"",
+                "kind": "property"
+            }
+        ],
+        "indent": 1
+    }
+]);