Superglobal variable assign is impure

src/Analyser/NodeScopeResolver.php

@@ -4403,6 +4403,9 @@ private function processAssignVar(
 			$hasYield = $result->hasYield();
 			$throwPoints = $result->getThrowPoints();
 			$impurePoints = $result->getImpurePoints();
+			if (in_array($var->name, Scope::SUPERGLOBAL_VARIABLES, true)) {
+				$impurePoints[] = new ImpurePoint($scope, $var, 'superglobal', 'assign to superglobal variable', true);
+			}
 			$assignedExpr = $this->unwrapAssign($assignedExpr);
 			$type = $scope->getType($assignedExpr);
 

tests/PHPStan/Rules/Pure/PureMethodRuleTest.php

@@ -107,6 +107,14 @@ public function testRule(): void
 				'Method PureMethod\ClassWithVoidMethods::privateEmptyVoidFunction() returns void but does not have any side effects.',
 				214,
 			],
+			[
+				'Impure assign to superglobal variable in pure method PureMethod\ClassWithVoidMethods::purePostGetAssign().',
+				230,
+			],
+			[
+				'Impure assign to superglobal variable in pure method PureMethod\ClassWithVoidMethods::purePostGetAssign().',
+				231,
+			],
 		]);
 	}
 

tests/PHPStan/Rules/Pure/data/pure-method.php

@@ -216,4 +216,21 @@ private function privateEmptyVoidFunction(): void
 
 	}
 
+	private function setPostAndGet(array $post = [], array $get = []): void
+	{
+		$_POST = $post;
+		$_GET = $get;
+	}
+
+	/**
+	 * @phpstan-pure
+	 */
+	public function purePostGetAssign(array $post = [], array $get = []): int
+	{
+		$_POST = $post;
+		$_GET = $get;
+
+		return 1;
+	}
+
 }