ForbidUselessNullableReturn: proper closure support (#99)

README.md

@@ -458,7 +458,7 @@ function example(MyClass $class) {
 ```
 
 ### forbidUselessNullableReturn
-- Denies marking function/method return type as nullable when null is never returned
+- Denies marking closure/function/method return type as nullable when null is never returned
 - Recommended to be used together with `uselessPrivatePropertyDefaultValue` and `UselessPrivatePropertyNullabilityRule`
 ```php
 public function example(int $foo): ?int { // null never returned

src/Rule/ForbidUselessNullableReturnRule.php

@@ -4,6 +4,7 @@
 
 use PhpParser\Node;
 use PHPStan\Analyser\Scope;
+use PHPStan\Node\ClosureReturnStatementsNode;
 use PHPStan\Node\ReturnStatementsNode;
 use PHPStan\Reflection\ParametersAcceptorSelector;
 use PHPStan\Rules\Rule;
@@ -33,12 +34,14 @@ public function processNode(Node $node, Scope $scope): array
         $verbosity = VerbosityLevel::precise();
         $methodReflection = $scope->getFunction();
 
-        if ($methodReflection === null) {
+        if ($node instanceof ClosureReturnStatementsNode) { // @phpstan-ignore-line ignore bc promise
+            $declaredType = $scope->getFunctionType($node->getClosureExpr()->getReturnType(), false, false);
+        } elseif ($methodReflection !== null) {
+            $declaredType = ParametersAcceptorSelector::selectSingle($methodReflection->getVariants())->getReturnType();
+        } else {
             return [];
         }
 
-        $declaredType = ParametersAcceptorSelector::selectSingle($methodReflection->getVariants())->getReturnType();
-
         if ($declaredType->isVoid()->yes()) {
             return [];
         }

tests/Rule/data/ForbidUselessNullableReturnRule/code.php

@@ -66,9 +66,24 @@ public function getStrict3(): int
         return $this->bar;
     }
 
+
+    public function voidMethod(): void
+    {
+        $fn = static function (array $string): ?array { // error: Declared return type array|null contains null, but it is never returned. Returned types: array.
+            return $string;
+        };
+
+        return;
+    }
+
+
 }
 
 function nullableFunction(int $int): ?int // error: Declared return type int|null contains null, but it is never returned. Returned types: int.
 {
     return $int;
 }
+
+$globalFn = static function (int $int): ?int { // error: Declared return type int|null contains null, but it is never returned. Returned types: int.
+    return $int;
+};