support deprecated magic __toString() in echo statement

src/Rules/Deprecations/EchoDeprecatedToStringRule.php

@@ -0,0 +1,94 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Deprecations;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\PropertyFetch;
+use PhpParser\Node\Identifier;
+use PHPStan\Analyser\Scope;
+use PHPStan\Analyser\VariableTypeHolder;
+use PHPStan\Broker\Broker;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\TypeUtils;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Rules\RuleLevelHelper;
+use PHPStan\Type\ErrorType;
+use PHPStan\Type\Type;
+use PHPStan\Type\VerbosityLevel;
+
+/**
+ * @implements \PHPStan\Rules\Rule<Echo_>
+ */
+class EchoDeprecatedToStringRule implements \PHPStan\Rules\Rule
+{
+
+	/**
+	 * @var RuleLevelHelper
+	 */
+	private $ruleLevelHelper;
+
+	public function __construct(RuleLevelHelper $ruleLevelHelper)
+	{
+		$this->ruleLevelHelper = $ruleLevelHelper;
+	}
+
+	public function getNodeType(): string
+	{
+		return Node\Stmt\Echo_::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if (DeprecatedScopeHelper::isScopeDeprecated($scope)) {
+			return [];
+		}
+
+		$messages = [];
+
+		foreach ($node->exprs as $key => $expr) {
+			if (!$expr instanceof Node\Expr\Variable) {
+				continue;
+			}
+
+			$type = $this->ruleLevelHelper->findTypeToCheck(
+				$scope,
+				$expr,
+				'',
+				static function (Type $type): bool {
+					return !$type->toString() instanceof ErrorType;
+				}
+			)->getType();
+
+			if (!$type instanceof ObjectType) {
+				continue;
+			}
+
+			$classReflection = $type->getClassReflection();
+			$methodReflection = $classReflection->getNativeMethod('__toString', $scope);
+
+			if (!$methodReflection->isDeprecated()->yes()) {
+				continue;
+			}
+
+			$description = $methodReflection->getDeprecatedDescription();
+			if ($description === null) {
+				$messages[] = sprintf(
+					'Call to deprecated method %s() of class %s.',
+					$methodReflection->getName(),
+					$methodReflection->getDeclaringClass()->getName()
+				);
+			} else {
+				$messages[] = sprintf(
+					"Call to deprecated method %s() of class %s:\n%s",
+					$methodReflection->getName(),
+					$methodReflection->getDeclaringClass()->getName(),
+					$description
+				);
+			}
+		}
+
+		return $messages;
+	}
+
+}

tests/Rules/Deprecations/EchoDeprecatedToStringRuleTest.php

@@ -0,0 +1,34 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Deprecations;
+
+use PHPStan\Rules\RuleLevelHelper;
+
+/**
+ * @extends \PHPStan\Testing\RuleTestCase<EchoDeprecatedToStringRule>
+ */
+class EchoDeprecatedToStringRuleTest extends \PHPStan\Testing\RuleTestCase
+{
+
+	protected function getRule(): \PHPStan\Rules\Rule
+	{
+		$ruleLevelHelper = new RuleLevelHelper($this->createBroker(), true, false, true);
+
+		return new EchoDeprecatedToStringRule($ruleLevelHelper);
+	}
+
+	public function testDeprecatedMagicMethodToStringCall(): void
+	{
+		require_once __DIR__ . '/data/echo-deprecated-magic-method-tostring.php';
+		$this->analyse(
+			[__DIR__ . '/data/echo-deprecated-magic-method-tostring.php'],
+			[
+				[
+					'Call to deprecated method __toString() of class CheckDeprecatedStaticMethodCall\MagicBar.',
+					6,
+				]
+			]
+		);
+	}
+
+}

tests/Rules/Deprecations/data/echo-deprecated-magic-method-tostring.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace CheckDeprecatedStaticMethodCall;
+
+$bar = new MagicBar();
+echo $bar;
+
+class MagicBar
+{
+	/**
+	 * @deprecated
+	 */
+	public function __toString()
+	{
+		return 'a string';
+	}
+}