Added WeakReference support (#2389)

src/Psalm/Internal/Stubs/CoreGenericClasses.php

@@ -1195,3 +1195,22 @@ class ReflectionClass implements Reflector {
     */
     public function newInstanceWithoutConstructor() : object;
 }
+
+/**
+ * @template-covariant T as object
+ * @psalm-immutable
+ */
+final class WeakReference
+{
+    // always fail
+    public function __construct();
+    /**
+     * @template TIn as object
+     * @param TIn $referent
+     * @return WeakReference<TIn>
+     */
+    public static function create(object $referent): WeakReference;
+
+    /** @return ?T */
+    public function get(): ?object;
+}

tests/Template/ClassTemplateTest.php

@@ -2067,6 +2067,22 @@ class ClassTemplateTest extends TestCase
 
                     takesInts((new ArrayCollection([ "a", "bc" ]))->map("strlen"));'
             ],
+            'weakReferenceIsTyped' => [
+                '<?php
+                    $e = new Exception;
+                    $r = WeakReference::create($e);
+                    $ex = $r->get();
+                ',
+                [ '$ex' => 'Exception|null' ],
+            ],
+            'weakReferenceIsCovariant' => [
+                '<?php
+                    /** @param WeakReference<Throwable> $_ref */
+                    function acceptsThrowableRef(WeakReference $_ref): void {}
+
+                    acceptsThrowableRef(WeakReference::create(new Exception));
+                '
+            ]
         ];
     }