[Rules] Skip valid return bool on ReturnNullOverFalseRule (#20)

* tests: Add new test cases for the issue

* [Rules] Skip valid return bool on ReturnNullOverFalseRule

---------

Co-authored-by: Michael Telgmann <m.telgmann@shopware.com>

src/Rules/ReturnNullOverFalseRule.php

@@ -11,6 +11,7 @@
 use PhpParser\NodeFinder;
 use PHPStan\Analyser\Scope;
 use PHPStan\Rules\Rule;
+use PHPStan\Type\BooleanType;
 use PHPStan\Type\Constant\ConstantBooleanType;
 use Rector\TypePerfect\Configuration;
 
@@ -62,20 +63,32 @@ public function processNode(Node $node, Scope $scope): array
         /** @var Return_[] $returns */
         $returns = $this->nodeFinder->findInstanceOf($node->stmts, Return_::class);
 
+        $hasFalseType = false;
+        $hasTrueType = false;
+
         foreach ($returns as $return) {
             if (! $return->expr instanceof Expr) {
                 continue;
             }
 
             $exprType = $scope->getType($return->expr);
             if (! $exprType instanceof ConstantBooleanType) {
+                if ($exprType instanceof BooleanType) {
+                    return [];
+                }
+
                 continue;
             }
 
             if ($exprType->getValue()) {
+                $hasTrueType = true;
                 continue;
             }
 
+            $hasFalseType = true;
+        }
+
+        if (! $hasTrueType && $hasFalseType) {
             return [
                 self::ERROR_MESSAGE,
             ];

tests/Rules/ReturnNullOverFalseRule/Fixture/CheckResultFromOtherMethod.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\TypePerfect\Tests\Rules\ReturnNullOverFalseRule\Fixture;
+
+class Loader
+{
+    /**
+     * @return bool
+     */
+    public function exists(string $name)
+    {
+        if (!$this->loadFromDb($name)) {
+            return false;
+        }
+
+        return true;
+    }
+
+    private function loadFromDb(string $name): ?array
+    {
+        if (mt_rand(1, 0)) {
+            return null;
+        }
+
+        return ['test' => 'foo'];
+    }
+}

tests/Rules/ReturnNullOverFalseRule/Fixture/CheckResultFromOtherMethod2.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\TypePerfect\Tests\Rules\ReturnNullOverFalseRule\Fixture;
+
+class Entity
+{
+    /**
+     * @param string $name
+     *
+     * @return bool
+     */
+    public function __isset($name)
+    {
+        if (!$this->isPropertyVisible($name)) {
+            return false;
+        }
+
+        return isset($this->$name);
+    }
+
+    private function isPropertyVisible(string $name): bool
+    {
+        if (mt_rand(1, 0)) {
+            return true;
+        }
+
+        return false;
+    }
+}

tests/Rules/ReturnNullOverFalseRule/ReturnNullOverFalseRuleTest.php

@@ -27,6 +27,8 @@ public static function provideData(): Iterator
             __DIR__ . '/Fixture/ReturnFalseOnly.php',
             [[ReturnNullOverFalseRule::ERROR_MESSAGE, 9]],
         ];
+        yield [__DIR__ . '/Fixture/CheckResultFromOtherMethod.php', []];
+        yield [__DIR__ . '/Fixture/CheckResultFromOtherMethod2.php', []];
 
         yield [__DIR__ . '/Fixture/SkipReturnBool.php', []];
     }