From 3d0ac6f15e4477480295331f72631067e6bc99c0 Mon Sep 17 00:00:00 2001
From: Ondrej Mirtes <ondrej@mirtes.cz>
Date: Tue, 22 Dec 2020 14:18:21 +0100
Subject: [PATCH] Arrow functions - allow more precise return type even when
 native return type is present

---
 src/Analyser/MutatingScope.php                   | 6 +++++-
 tests/PHPStan/Analyser/NodeScopeResolverTest.php | 8 ++++++--
 tests/PHPStan/Analyser/data/arrow-functions.php  | 1 +
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index 501588eaf5..a87dc9e1f7 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -80,6 +80,7 @@
 use PHPStan\Type\ThisType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\TypehintHelper;
 use PHPStan\Type\TypeTraverser;
 use PHPStan\Type\TypeUtils;
 use PHPStan\Type\TypeWithClassName;
@@ -1306,8 +1307,11 @@ private function resolveType(Expr $node): Type
 				);
 			}
 
-			if ($node->returnType === null && $node instanceof Expr\ArrowFunction) {
+			if ($node instanceof Expr\ArrowFunction) {
 				$returnType = $this->getType($node->expr);
+				if ($node->returnType !== null) {
+					$returnType = TypehintHelper::decideType($this->getFunctionType($node->returnType, false, false), $returnType);
+				}
 			} else {
 				$returnType = $this->getFunctionType($node->returnType, $node->returnType === null, false);
 			}
diff --git a/tests/PHPStan/Analyser/NodeScopeResolverTest.php b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
index a96fd1a59e..e097c3d8e7 100644
--- a/tests/PHPStan/Analyser/NodeScopeResolverTest.php
+++ b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
@@ -10915,13 +10915,17 @@ public function dataArrowFunctions(): array
 	{
 		return [
 			[
-				'Closure(string): int',
+				'Closure(string): 1',
 				'$x',
 			],
 			[
-				'int',
+				'1',
 				'$x()',
 			],
+			[
+				'array(\'a\' => 1, \'b\' => 2)',
+				'$y()',
+			],
 		];
 	}
 
diff --git a/tests/PHPStan/Analyser/data/arrow-functions.php b/tests/PHPStan/Analyser/data/arrow-functions.php
index 2e9bc13ffb..0a94933360 100644
--- a/tests/PHPStan/Analyser/data/arrow-functions.php
+++ b/tests/PHPStan/Analyser/data/arrow-functions.php
@@ -8,6 +8,7 @@ class Foo
 	public function doFoo()
 	{
 		$x = fn(string $str): int => 1;
+		$y = fn(): array => ['a' => 1, 'b' => 2];
 		die;
 	}