VoidType - accept null

src/Type/VoidType.php

@@ -66,7 +66,7 @@ public function acceptsWithReason(Type $type, bool $strictTypes): AcceptsResult
 			return $type->isAcceptedWithReasonBy($this, $strictTypes);
 		}
 
-		return AcceptsResult::createFromBoolean($type instanceof self);
+		return new AcceptsResult($type->isVoid()->or($type->isNull()), []);
 	}
 
 	public function isSuperTypeOf(Type $type): TrinaryLogic

tests/PHPStan/Rules/Methods/ReturnTypeRuleTest.php

@@ -988,4 +988,9 @@ public function testBug6653(): void
 		$this->analyse([__DIR__ . '/data/bug-6653.php'], []);
 	}
 
+	public function testBug10291(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-10291.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Methods/data/bug-10291.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Bug10291;
+
+class HelloWorld
+{
+	/** @return void|int */
+	public function sayHello()
+	{
+		return rand(0, 1) ? 17 : null;
+	}
+
+	/**
+	 * @param bool $something
+	 * @return void|int
+	 */
+	public function sayHello2($something)
+	{
+		if ($something) {
+			return rand(0, 1);
+		} else {
+			return $this->myrand();
+		}
+	}
+}