Prevent mixed erasure in get_class call

src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php

@@ -1346,6 +1346,8 @@ class FunctionCallAnalyzer extends CallAnalyzer
                                     $class_type->defining_class
                                 );
                             }
+                        } else {
+                            $class_string_types[] = new Type\Atomic\TClassString();
                         }
                     }
 

tests/SwitchTypeTest.php

@@ -937,6 +937,28 @@ class SwitchTypeTest extends TestCase
                             echo "bar";
                     }'
             ],
+            'switchGetClassProperty' => [
+                '<?php
+                    class A {}
+                    class B {}
+
+                    class C {
+                        /** @var mixed */
+                        public $a;
+
+                        function foo() : void {
+                            if (rand(0, 1)) {
+                                $this->a = new A();
+                            }
+
+                            /** @psalm-suppress MixedArgument */
+                            switch (get_class($this->a)) {
+                                case B::class:
+                                    echo "here";
+                            }
+                        }
+                    }',
+            ],
         ];
     }