From 4d9a202ef15424d16b723820073b3066d3098351 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Fri, 5 Oct 2018 16:23:42 -0700
Subject: [PATCH] Properly widen initializer types in binding elements

---
 src/compiler/checker.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 21518ca34d5..e200730bc87 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -4704,11 +4704,11 @@ namespace ts {
             }
             // In strict null checking mode, if a default value of a non-undefined type is specified, remove
             // undefined from the final type.
-            if (strictNullChecks && declaration.initializer && !(getFalsyFlags(checkExpressionCached(declaration.initializer)) & TypeFlags.Undefined)) {
+            if (strictNullChecks && declaration.initializer && !(getFalsyFlags(checkDeclarationInitializer(declaration)) & TypeFlags.Undefined)) {
                 type = getTypeWithFacts(type, TypeFacts.NEUndefined);
             }
             return declaration.initializer && !getEffectiveTypeAnnotationNode(walkUpBindingElementsAndPatterns(declaration)) ?
-                getUnionType([type, checkExpressionCached(declaration.initializer)], UnionReduction.Subtype) :
+                getUnionType([type, checkDeclarationInitializer(declaration)], UnionReduction.Subtype) :
                 type;
         }