From 4d7ec380a9a5d6f7e2f882d6bae9557d7414afb5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=8E=8B=E6=96=87=E7=92=90?= <kingwenlu@gmail.com>
Date: Tue, 26 Feb 2019 10:54:01 +0800
Subject: [PATCH] check completions with assignable rather than identity

---
 src/compiler/checker.ts                        |  2 +-
 .../completionsWithOptionalProperties.ts       | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/completionsWithOptionalProperties.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ddc958df0b4..c882227ba0c 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7406,7 +7406,7 @@ namespace ts {
                 const nameType = property.name && getLiteralTypeFromPropertyName(property.name);
                 const name = nameType && isTypeUsableAsPropertyName(nameType) ? getPropertyNameFromType(nameType) : undefined;
                 const expected = name === undefined ? undefined : getTypeOfPropertyOfType(contextualType, name);
-                return !!expected && isLiteralType(expected) && !isTypeIdenticalTo(getTypeOfNode(property), expected);
+                return !!expected && isLiteralType(expected) && !isTypeAssignableTo(getTypeOfNode(property), expected);
             });
         }
 
diff --git a/tests/cases/fourslash/completionsWithOptionalProperties.ts b/tests/cases/fourslash/completionsWithOptionalProperties.ts
new file mode 100644
index 00000000000..e40029ddefa
--- /dev/null
+++ b/tests/cases/fourslash/completionsWithOptionalProperties.ts
@@ -0,0 +1,18 @@
+/// <reference path="fourslash.ts" />
+// @strict: true
+
+//// interface Options {
+////     hello?: boolean;
+////     world?: boolean;
+//// }
+//// declare function foo(options?: Options): void;
+//// foo({
+////     hello: true,
+////     /**/
+//// });
+
+verify.completions({
+    marker: "",
+    includes: ['world']
+});
+