ForbidUselessNullableReturnRule: ignore for overridable errors

src/Rule/ForbidUselessNullableReturnRule.php

@@ -6,6 +6,7 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\Node\ClosureReturnStatementsNode;
 use PHPStan\Node\ReturnStatementsNode;
+use PHPStan\Reflection\MethodReflection;
 use PHPStan\Rules\IdentifierRuleError;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
@@ -38,6 +39,10 @@ public function processNode(
         $verbosity = VerbosityLevel::precise();
         $methodReflection = $scope->getFunction();
 
+        if ($methodReflection instanceof MethodReflection && $this->isOverridable($methodReflection)) {
+            return [];
+        }
+
         if ($node instanceof ClosureReturnStatementsNode) {
             $declaredType = $scope->getFunctionType($node->getClosureExpr()->getReturnType(), false, false);
         } elseif ($methodReflection !== null) {
@@ -80,4 +85,9 @@ public function processNode(
         return [];
     }
 
+    private function isOverridable(MethodReflection $methodReflection): bool
+    {
+        return !$methodReflection->isFinal()->yes() && !$methodReflection->isPrivate() && !$methodReflection->isStatic() && !$methodReflection->getDeclaringClass()->isFinalByKeyword();
+    }
+
 }

tests/Rule/data/ForbidUselessNullableReturnRule/code.php

@@ -2,7 +2,7 @@
 
 namespace ForbidUselessNullableReturnRule;
 
-class ExampleClass {
+final class ExampleClass {
 
     private ?int $foo;
 
@@ -87,3 +87,30 @@ function nullableFunction(int $int): ?int // error: Declared return type int|nul
 $globalFn = static function (int $int): ?int { // error: Declared return type int|null contains null, but it is never returned. Returned types: int.
     return $int;
 };
+
+class NonFinalClass {
+    public static function staticMethod(): ?int // error: Declared return type int|null contains null, but it is never returned. Returned types: 1.
+    {
+        return 1;
+    }
+
+    final public function finalMethod(): ?int // error: Declared return type int|null contains null, but it is never returned. Returned types: 1.
+    {
+        return 1;
+    }
+
+    private function privateMethod(): ?int // error: Declared return type int|null contains null, but it is never returned. Returned types: 1.
+    {
+        return 1;
+    }
+
+    public function publicMethod(): ?int
+    {
+        return 1;
+    }
+
+    protected function protectedMethod(): ?int
+    {
+        return 1;
+    }
+}