Fix #561 - add all the do-defined vars before checking loop

src/Psalm/Checker/Statements/Block/DoChecker.php

@@ -59,6 +59,12 @@ class DoChecker
             }
         }
 
+        foreach ($do_context->vars_in_scope as $var_id => $type) {
+            if (!isset($context->vars_in_scope[$var_id])) {
+                $context->vars_in_scope[$var_id] = clone $type;
+            }
+        }
+
         $mixed_var_ids = [];
 
         foreach ($do_context->vars_in_scope as $var_id => $type) {

tests/LoopScopeTest.php

@@ -975,6 +975,14 @@ class LoopScopeTest extends TestCase
                         }
                     }',
             ],
+            'doWhileDefinedVar' => [
+                '<?php
+                    $value = null;
+                    do {
+                        $count = rand(0, 1);
+                        $value = 6;
+                    } while ($count);',
+            ],
         ];
     }