From 442c307b301d761285e21382be67674e428eb48e Mon Sep 17 00:00:00 2001
From: Matthew Brown <github@muglug.com>
Date: Mon, 27 May 2019 00:12:57 -0400
Subject: [PATCH] Prevent removing null from single null type

---
 src/Psalm/Type/Union.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Psalm/Type/Union.php b/src/Psalm/Type/Union.php
index fb9740d59fc..24d9f73275c 100644
--- a/src/Psalm/Type/Union.php
+++ b/src/Psalm/Type/Union.php
@@ -1010,7 +1010,7 @@ public function replaceTemplateTypesWithStandins(
                         if ($input_type) {
                             $generic_param = clone $input_type;
 
-                            if ($this->isNullable() && $generic_param->isNullable()) {
+                            if ($this->isNullable() && $generic_param->isNullable() && !$generic_param->isNull()) {
                                 $generic_param->removeType('null');
                             }