Do not report invariant template type mismatch when both type arguments are the same template parameter narrowed by control flow

src/Type/Generic/TemplateTypeVariance.php

@@ -176,6 +176,13 @@ public function isValidVariance(TemplateType $templateType, Type $a, Type $b): I
 		}
 
 		if ($this->invariant()) {
+			if ($a instanceof TemplateType && $b instanceof TemplateType
+				&& $a->getScope()->equals($b->getScope())
+				&& $a->getName() === $b->getName()
+			) {
+				return IsSuperTypeOfResult::createYes();
+			}
+
 			$result = $a->equals($b);
 			$reasons = [];
 			if (!$result) {

tests/PHPStan/Rules/Functions/ReturnTypeRuleTest.php

@@ -451,4 +451,11 @@ public function testBug13565(): void
 		]);
 	}
 
+	public function testBug13190(): void
+	{
+		$this->checkNullables = true;
+		$this->checkExplicitMixed = false;
+		$this->analyse([__DIR__ . '/data/bug-13190.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Functions/data/bug-13190.php

@@ -0,0 +1,55 @@
+<?php // lint >= 8.0
+declare(strict_types = 1);
+
+namespace Bug13190;
+
+/**
+ * @template T
+ */
+interface Box
+{
+	/**
+	 * @return T
+	 */
+	public function toInner(): mixed;
+}
+
+/**
+ * @template T
+ *
+ * @implements Box<T>
+ */
+final class BoxImpl implements Box
+{
+	/**
+	 * @param T $value
+	 */
+	public function __construct(
+		private mixed $value,
+	) {}
+
+	/**
+	 * @return T
+	 */
+	#[\Override]
+	public function toInner(): mixed
+	{
+		return $this->value;
+	}
+}
+
+/**
+ * @template T
+ *
+ * @param T|Box<T> $to_box
+ *
+ * @return Box<T>
+ */
+function inbox($to_box): Box
+{
+	if ($to_box instanceof Box) {
+		return $to_box;
+	} else {
+		return new BoxImpl($to_box);
+	}
+}