From 995732fad27ed88d0b2d75333b72e53c0f8eb5e2 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Thu, 3 Nov 2016 15:35:10 -0700
Subject: [PATCH] Add undefined to default-valued parameters

When --strictNullChecks is on
---
 src/compiler/checker.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 28b14502af9..a459db40e1b 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -3206,7 +3206,8 @@ namespace ts {
             // Use the type of the initializer expression if one is present
             if (declaration.initializer) {
                 const type = checkDeclarationInitializer(declaration);
-                return addOptionality(type, /*optional*/ declaration.questionToken && includeOptionality);
+                const isOptional = declaration.questionToken || (declaration.initializer && declaration.kind === SyntaxKind.Parameter);
+                return addOptionality(type, isOptional && includeOptionality);
             }
 
             // If it is a short-hand property assignment, use the type of the identifier