qa: introduce psalm stub for psr/http-message UriInterface

This also requires `Uri` to be `psalm-immutable`.

Signed-off-by: Maximilian Bösing <[email protected]>

.gitattributes

@@ -12,3 +12,4 @@
 /psalm.xml.dist export-ignore
 /renovate.json export-ignore
 /test/ export-ignore
+/psalm/ export-ignore

psalm.xml.dist

@@ -14,6 +14,10 @@
         </ignoreFiles>
     </projectFiles>
 
+    <stubs>
+        <file name="psalm/http-message-stubs/UriInterface.phpstub"/>
+    </stubs>
+
     <issueHandlers>
         <DeprecatedFunction>
             <errorLevel type="suppress">

psalm/http-message-stubs/UriInterface.phpstub

@@ -0,0 +1,18 @@
+<?php
+declare(strict_types=1);
+
+namespace Psr\Http\Message;
+
+/**
+ * [...]
+ * Instances of this interface are considered immutable; all methods that
+ * might change state MUST be implemented such that they retain the internal
+ * state of the current instance and return an instance that contains the
+ * changed state.
+ * [...]
+ * @psalm-immutable
+ */
+interface UriInterface
+{
+
+}

src/Uri.php

@@ -38,6 +38,8 @@
  * might change state are implemented such that they retain the internal
  * state of the current instance and return a new instance that contains the
  * changed state.
+ *
+ * @psalm-immutable
  */
 class Uri implements UriInterface, Stringable
 {
@@ -67,8 +69,7 @@ class Uri implements UriInterface, Stringable
 
     private string $host = '';
 
-    /** @var int|null */
-    private $port;
+    private ?int $port = null;
 
     private string $path = '';