Implement FinalPrivateConstantRule

Makefile

@@ -107,6 +107,7 @@ lint:
 		--exclude tests/PHPStan/Rules/Properties/data/final-property-hooks.php \
 		--exclude tests/PHPStan/Rules/Properties/data/final-properties.php \
 		--exclude tests/PHPStan/Rules/Properties/data/property-in-interface-explicit-abstract.php \
+		--exclude tests/PHPStan/Rules/Constants/data/final-private-const.php \
 		src tests
 
 cs:

conf/config.level0.neon

@@ -46,6 +46,7 @@ rules:
 	- PHPStan\Rules\Constants\FinalConstantRule
 	- PHPStan\Rules\Constants\MagicConstantContextRule
 	- PHPStan\Rules\Constants\NativeTypedClassConstantRule
+	- PHPStan\Rules\Constants\FinalPrivateConstantRule
 	- PHPStan\Rules\EnumCases\EnumCaseAttributesRule
 	- PHPStan\Rules\Exceptions\NoncapturingCatchRule
 	- PHPStan\Rules\Exceptions\ThrowExpressionRule

src/Rules/Constants/FinalPrivateConstantRule.php

@@ -0,0 +1,49 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Constants;
+
+use PhpParser\Node;
+use PhpParser\Node\Stmt\ClassConst;
+use PHPStan\Analyser\Scope;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\ShouldNotHappenException;
+use function sprintf;
+
+/** @implements Rule<ClassConst> */
+final class FinalPrivateConstantRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return ClassConst::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if (!$scope->isInClass()) {
+			throw new ShouldNotHappenException();
+		}
+		$classReflection = $scope->getClassReflection();
+
+		if (!$node->isFinal()) {
+			return [];
+		}
+
+		if (!$node->isPrivate()) {
+			return [];
+		}
+
+		$errors = [];
+		foreach ($node->consts as $classConstNode) {
+			$errors[] = RuleErrorBuilder::message(sprintf(
+				'Private constant %s::%s() cannot be final as it is never overridden by other classes.',
+				$classReflection->getDisplayName(),
+				$classConstNode->name->name,
+			))->identifier('classConstant.finalPrivate')->nonIgnorable()->build();
+		}
+
+		return $errors;
+	}
+
+}

tests/PHPStan/Rules/Constants/FinalPrivateConstantRuleTest.php

@@ -0,0 +1,27 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Constants;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/** @extends RuleTestCase<FinalPrivateConstantRule> */
+class FinalPrivateConstantRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new FinalPrivateConstantRule();
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/final-private-const.php'], [
+			[
+				'Private constant FinalPrivateConstants\User::FINAL_PRIVATE() cannot be final as it is never overridden by other classes.',
+				8,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/Constants/data/final-private-const.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace FinalPrivateConstants;
+
+class User
+{
+	private const PRIVATE = 'mailto: example.org';
+	final private const FINAL_PRIVATE = 'mailto: example.org';
+	final protected const PROTECTED = 'mailto: example.org';
+	final public const PUBLIC = 'mailto: example.org';
+}