From 5c99c67b4bd7b15f86db75909929b79d433e4b71 Mon Sep 17 00:00:00 2001
From: Ryan Cavanaugh <RyanCavanaugh@users.noreply.github.com>
Date: Thu, 7 Dec 2017 12:16:53 -0800
Subject: [PATCH] Fixes #20542

---
 src/compiler/checker.ts                             | 7 ++++++-
 tests/cases/fourslash/typeToStringCrashInCodeFix.ts | 6 ++++++
 2 files changed, 12 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/typeToStringCrashInCodeFix.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 269c55145ec..5b481ef4721 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -3951,7 +3951,12 @@ namespace ts {
                     writePunctuation(writer, SyntaxKind.CloseBracketToken);
                     writePunctuation(writer, SyntaxKind.ColonToken);
                     writeSpace(writer);
-                    buildTypeDisplay(info.type, writer, enclosingDeclaration, globalFlags, symbolStack);
+                    if (info.type) {
+                        buildTypeDisplay(info.type, writer, enclosingDeclaration, globalFlags, symbolStack);
+                    }
+                    else {
+                        writeKeyword(writer, SyntaxKind.AnyKeyword);
+                    }
                     writePunctuation(writer, SyntaxKind.SemicolonToken);
                     writer.writeLine();
                 }
diff --git a/tests/cases/fourslash/typeToStringCrashInCodeFix.ts b/tests/cases/fourslash/typeToStringCrashInCodeFix.ts
new file mode 100644
index 00000000000..05cf00cb4ce
--- /dev/null
+++ b/tests/cases/fourslash/typeToStringCrashInCodeFix.ts
@@ -0,0 +1,6 @@
+/// <reference path="fourslash.ts" />
+
+// @noImplicitAny: true
+//// function f(y, z = { p: y[
+
+verify.getAndApplyCodeFix();