From 191b9750c3f7880f4b33c5c08024832068117ca0 Mon Sep 17 00:00:00 2001
From: Andy <anhans@microsoft.com>
Date: Tue, 9 Jan 2018 11:22:15 -0800
Subject: [PATCH] Clear jsDocCache for reused nodes (#21099)

---
 src/compiler/parser.ts                        |  5 +++++
 tests/cases/fourslash/editClearsJsDocCache.ts | 14 ++++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 tests/cases/fourslash/editClearsJsDocCache.ts

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 6503e6bf421..bae9f0594ed 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -1679,6 +1679,11 @@ namespace ts {
                 return undefined;
             }
 
+            if ((node as JSDocContainer).jsDocCache) {
+                // jsDocCache may include tags from parent nodes, which might have been modified.
+                (node as JSDocContainer).jsDocCache = undefined;
+            }
+
             return node;
         }
 
diff --git a/tests/cases/fourslash/editClearsJsDocCache.ts b/tests/cases/fourslash/editClearsJsDocCache.ts
new file mode 100644
index 00000000000..0ffc351300f
--- /dev/null
+++ b/tests/cases/fourslash/editClearsJsDocCache.ts
@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts'/>
+
+// @allowJs: true
+
+// @Filename: /a.js
+/////** @type {/*type*/number} */
+////let /*x*/x;
+
+verify.quickInfoAt("x", "let x: number");
+
+goTo.marker("type");
+edit.replace(test.markers()[0].position, "number".length, "string");
+
+verify.quickInfoAt("x", "let x: string");