From d2114541a5402cb7fcff99548b246ff187e9ac68 Mon Sep 17 00:00:00 2001
From: Simon Podlipsky <simon@podlipsky.net>
Date: Thu, 18 Apr 2024 12:31:59 +0200
Subject: [PATCH] feat: narrow ResultInterface to concrete implementation after
 calling `isSucceeded()` and `isFailed()` (#466)

---
 src/Psl/Result/ResultInterface.php            |  4 ++
 .../Result/result_interface.php               | 42 +++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 tests/static-analysis/Result/result_interface.php

diff --git a/src/Psl/Result/ResultInterface.php b/src/Psl/Result/ResultInterface.php
index a37731cb..1e180e49 100644
--- a/src/Psl/Result/ResultInterface.php
+++ b/src/Psl/Result/ResultInterface.php
@@ -115,6 +115,8 @@ public function getThrowable(): Throwable;
      * @return bool - `true` if the operation succeeded; `false` otherwise
      *
      * @psalm-mutation-free
+     *
+     * @psalm-assert-if-true Success<T> $this
      */
     public function isSucceeded(): bool;
 
@@ -126,6 +128,8 @@ public function isSucceeded(): bool;
      * @return bool - `true` if the operation failed; `false` otherwise
      *
      * @psalm-mutation-free
+     *
+     * @psalm-assert-if-true Failure<T> $this
      */
     public function isFailed(): bool;
 
diff --git a/tests/static-analysis/Result/result_interface.php b/tests/static-analysis/Result/result_interface.php
new file mode 100644
index 00000000..e5f7d0d1
--- /dev/null
+++ b/tests/static-analysis/Result/result_interface.php
@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\Tests\StaticAnalysis\Iter;
+
+use Exception;
+use Psl\Result\Failure;
+use Psl\Result\ResultInterface;
+use Psl\Result\Success;
+
+/**
+ * @param ResultInterface<int> $result
+ *
+ * @throws Exception
+ *
+ * @return Failure<int, Exception>
+ */
+function return_failure(ResultInterface $result): Failure
+{
+    if ($result->isFailed()) {
+        return $result;
+    }
+
+    throw new Exception();
+}
+
+/**
+ * @param ResultInterface<int> $result
+ *
+ * @throws Exception
+ *
+ * @return Success<int>
+ */
+function return_success(ResultInterface $result): Success
+{
+    if ($result->isSucceeded()) {
+        return $result;
+    }
+
+    throw new Exception();
+}