From c549bb57375ee686477e88fd21182c4b5b5c9e9b Mon Sep 17 00:00:00 2001
From: Andy <anhans@microsoft.com>
Date: Wed, 17 Jan 2018 11:27:21 -0800
Subject: [PATCH] Fix bug: getNonNullableType before getting signatures of
 method (#21212)

---
 src/compiler/checker.ts                            | 2 +-
 tests/cases/fourslash/completionsOptionalMethod.ts | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/completionsOptionalMethod.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 489fff16e2c..b3f06788131 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15815,7 +15815,7 @@ namespace ts {
         }
         function isValidMethodAccess(method: Symbol, type: Type) {
             const propType = getTypeOfFuncClassEnumModule(method);
-            const signatures = getSignaturesOfType(propType, SignatureKind.Call);
+            const signatures = getSignaturesOfType(getNonNullableType(propType), SignatureKind.Call);
             Debug.assert(signatures.length !== 0);
             return signatures.some(sig => {
                 const thisType = getThisTypeOfSignature(sig);
diff --git a/tests/cases/fourslash/completionsOptionalMethod.ts b/tests/cases/fourslash/completionsOptionalMethod.ts
new file mode 100644
index 00000000000..72399f177f2
--- /dev/null
+++ b/tests/cases/fourslash/completionsOptionalMethod.ts
@@ -0,0 +1,8 @@
+/// <reference path="fourslash.ts" />
+
+// @strictNullChecks: true
+
+////declare const x: { m?(): void };
+////x./**/
+
+verify.completionsAt("", ["m"]);