fix: dynamic variable error on isset

Author: ga-devfront

src/Rules/IssetCheck.php

@@ -41,6 +41,14 @@ public function __construct(
 	 */
 	public function check(Expr $expr, Scope $scope, string $operatorDescription, string $identifier, callable $typeMessageCallback, ?IdentifierRuleError $error = null): ?IdentifierRuleError
 	{
+		// [FIX] Ignore isset($$foo): dynamic variable
+		if (
+			$expr instanceof Node\Expr\Variable &&
+			$expr->name instanceof Node\Expr\Variable
+		) {
+			return null;
+		}
+
 		// mirrored in PHPStan\Analyser\MutatingScope::issetCheck()
 		if ($expr instanceof Node\Expr\Variable && is_string($expr->name)) {
 			$hasVariable = $scope->hasVariableType($expr->name);

tests/PHPStan/Rules/Variables/IssetRuleTest.php

@@ -485,4 +485,10 @@ public function testIssetAfterRememberedConstructor(): void
 		]);
 	}
 
+	public function testDynamicVariable(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+
+		$this->analyse([__DIR__ . '/data/dynamic-variable.php'], []);
+	}
 }

tests/PHPStan/Rules/Variables/data/dynamic-variable.php

@@ -0,0 +1,7 @@
+<?php declare(strict_types = 1);
+
+$foo = 'bar';
+
+if (!isset($$foo)) {
+	echo 'Wololo';
+}