From adc860893e59991e07cf96758d60b22a49040e7d Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Mon, 2 May 2016 16:24:06 -0700
Subject: [PATCH] Initial type of variable is union of declared type and
 undefined

---
 src/compiler/checker.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 8b53ecbf191..831d7960d23 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7989,7 +7989,7 @@ namespace ts {
             const defaultsToDeclaredType = !strictNullChecks || type.flags & TypeFlags.Any || !declaration ||
                 getRootDeclaration(declaration).kind === SyntaxKind.Parameter || isInAmbientContext(declaration) ||
                 getContainingFunctionOrModule(declaration) !== getContainingFunctionOrModule(node);
-            const flowType = getFlowTypeOfReference(node, type, defaultsToDeclaredType ? type : undefinedType);
+            const flowType = getFlowTypeOfReference(node, type, defaultsToDeclaredType ? type : addNullableKind(type, TypeFlags.Undefined));
             if (strictNullChecks && !(type.flags & TypeFlags.Any) && !(getNullableKind(type) & TypeFlags.Undefined) && getNullableKind(flowType) & TypeFlags.Undefined) {
                 error(node, Diagnostics.Variable_0_is_used_before_being_assigned, symbolToString(symbol));
                 // Return the declared type to reduce follow-on errors