From 2dc86651a411df6c673079b37df20103705bb4d2 Mon Sep 17 00:00:00 2001
From: Matt Brown <github@muglug.com>
Date: Tue, 9 Feb 2021 14:13:18 -0500
Subject: [PATCH] Check context var exists

---
 .../Internal/Analyzer/Statements/Block/SwitchAnalyzer.php  | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/Psalm/Internal/Analyzer/Statements/Block/SwitchAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Block/SwitchAnalyzer.php
index 806fedceb..1ef5d7c27 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Block/SwitchAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Block/SwitchAnalyzer.php
@@ -197,7 +197,12 @@ class SwitchAnalyzer
             $stmt->allMatched = true;
         } elseif ($switch_scope->possibly_redefined_vars) {
             foreach ($switch_scope->possibly_redefined_vars as $var_id => $type) {
-                $context->vars_in_scope[$var_id] = Type::combineUnionTypes($type, $context->vars_in_scope[$var_id]);
+                if (isset($context->vars_in_scope[$var_id])) {
+                    $context->vars_in_scope[$var_id] = Type::combineUnionTypes(
+                        $type,
+                        $context->vars_in_scope[$var_id]
+                    );
+                }
             }
         }