detect override of deprecated constant

rules.neon

@@ -8,6 +8,8 @@ services:
         class: PHPStan\Rules\Deprecations\OverrideDeprecatedPropertyRule
     -
         class: PHPStan\Rules\Deprecations\OverrideDeprecatedMethodRule
+    -
+        class: PHPStan\Rules\Deprecations\OverrideDeprecatedConstantRule
 
 rules:
 	- PHPStan\Rules\Deprecations\AccessDeprecatedPropertyRule
@@ -32,3 +34,5 @@ conditionalTags:
         phpstan.rules.rule: %featureToggles.bleedingEdge%
     PHPStan\Rules\Deprecations\OverrideDeprecatedMethodRule:
         phpstan.rules.rule: %featureToggles.bleedingEdge%
+    PHPStan\Rules\Deprecations\OverrideDeprecatedConstantRule:
+        phpstan.rules.rule: %featureToggles.bleedingEdge%

src/Rules/Deprecations/OverrideDeprecatedConstantRule.php

@@ -0,0 +1,64 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Deprecations;
+
+use PhpParser\Node;
+use PhpParser\Node\Stmt\ClassConst;
+use PHPStan\Analyser\Scope;
+use PHPStan\Rules\Rule;
+use function sprintf;
+
+/**
+ * @implements Rule<ClassConst>
+ */
+class OverrideDeprecatedConstantRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return ClassConst::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if (DeprecatedScopeHelper::isScopeDeprecated($scope)) {
+			return [];
+		}
+
+		if (!$scope->isInClass()) {
+			return [];
+		}
+
+		if ($node->isPrivate()) {
+			return [];
+		}
+
+		$class = $scope->getClassReflection();
+
+		$parents = $class->getParents();
+
+		$name = (string) $node->consts[0]->name;
+
+		foreach ($parents as $parent) {
+			if (!$parent->hasConstant($name)) {
+				continue;
+			}
+
+			$parentConst = $parent->getConstant($name);
+
+			if (!$parentConst->isDeprecated()->yes()) {
+				return [];
+			}
+
+			return [sprintf(
+				'Class %s overrides deprecated const %s of class %s.',
+				$class->getName(),
+				$name,
+				$parent->getName()
+			)];
+		}
+
+		return [];
+	}
+
+}

tests/Rules/Deprecations/OverrideDeprecatedConstantRuleTest.php

@@ -0,0 +1,32 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Deprecations;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<OverrideDeprecatedConstantRule>
+ */
+class OverrideDeprecatedConstantRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new OverrideDeprecatedConstantRule();
+	}
+
+	public function testDeprecatedConstantOverride(): void
+	{
+		$this->analyse(
+			[__DIR__ . '/data/override-deprecated-constant.php'],
+			[
+				[
+					'Class OverrideDeprecatedConstant\Child overrides deprecated const FOO of class OverrideDeprecatedConstant\Foo.',
+					20,
+				],
+			]
+		);
+	}
+
+}

tests/Rules/Deprecations/data/override-deprecated-constant.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace OverrideDeprecatedConstant;
+
+class Foo
+{
+	/**
+	 * @deprecated
+	 */
+	public const FOO = '';
+
+	/**
+	 * @deprecated
+	 */
+	private const BAR = '';
+}
+
+class Child extends Foo
+{
+	public const FOO = '';
+
+	private const BAR = '';
+}