From af3f737451453ed812817d8b56bc62a8c3e8bc56 Mon Sep 17 00:00:00 2001
From: Andy <anhans@microsoft.com>
Date: Thu, 26 Jul 2018 17:26:58 -0700
Subject: [PATCH] Fix bug for isValidTrigger when contextToken is undefined
 (#25993)

---
 src/services/completions.ts                          | 2 +-
 tests/cases/fourslash/completionsTriggerCharacter.ts | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/services/completions.ts b/src/services/completions.ts
index 232514722cb..4a62b353101 100644
--- a/src/services/completions.ts
+++ b/src/services/completions.ts
@@ -42,7 +42,7 @@ namespace ts.Completions {
         }
 
         const contextToken = findPrecedingToken(position, sourceFile);
-        if (triggerCharacter && !isValidTrigger(sourceFile, triggerCharacter, contextToken!, position)) return undefined; // TODO: GH#18217
+        if (triggerCharacter && (!contextToken || !isValidTrigger(sourceFile, triggerCharacter, contextToken, position))) return undefined;
 
         if (isInString(sourceFile, position, contextToken)) {
             return !contextToken || !isStringLiteralLike(contextToken)
diff --git a/tests/cases/fourslash/completionsTriggerCharacter.ts b/tests/cases/fourslash/completionsTriggerCharacter.ts
index e4709ab48f7..a58ff2edc5f 100644
--- a/tests/cases/fourslash/completionsTriggerCharacter.ts
+++ b/tests/cases/fourslash/completionsTriggerCharacter.ts
@@ -2,6 +2,7 @@
 
 // @jsx: preserve
 
+//////</*comment*/
 ////const x: "a" | "b" = "/*openQuote*/"/*closeQuote*/;
 ////const y: 'a' | 'b' = '/*openSingleQuote*/'/*closeSingleQuote*/;
 ////const z: 'a' | 'b' = `/*openTemplate*/`/*closeTemplate*/;
@@ -28,6 +29,8 @@
 ////const divide = 1 //*divide*/
 
 verify.completions(
+    { marker: "comment", exact: undefined, triggerCharacter: "<" },
+
     { marker: "openQuote", exact: ["a", "b"], triggerCharacter: '"' },
     { marker: "closeQuote", exact: undefined, triggerCharacter: '"' },