Add non regression test

Author: VincentLanglet

tests/PHPStan/Rules/Properties/TypesAssignedToPropertiesRuleTest.php

@@ -1025,6 +1025,13 @@ public function testBug12250(): void
 		$this->analyse([__DIR__ . '/data/bug-12250.php'], []);
 	}
 
+	public function testBug12688(): void
+	{
+		$this->checkExplicitMixed = true;
+		$this->checkImplicitMixed = true;
+		$this->analyse([__DIR__ . '/data/bug-12688.php'], []);
+	}
+
 	public function testBug4525(): void
 	{
 		$this->analyse([__DIR__ . '/data/bug-4525.php'], []);

tests/PHPStan/Rules/Properties/data/bug-12688.php

@@ -0,0 +1,54 @@
+<?php // lint >= 8.1
+
+namespace Bug12688;
+
+/**
+ * @template T = mixed
+ */
+interface I {}
+
+/**
+ * @implements I<mixed>
+ */
+enum E implements I
+{
+	case E;
+}
+
+/**
+ * @template T
+ */
+final class TemplateWithoutDefaultWorks
+{
+	/**
+	 * @var I<T>
+	 */
+	public readonly I $i;
+
+	/**
+	 * @param I<T> $i
+	 */
+	public function __construct(I $i = E::E)
+	{
+		$this->i = $i;
+	}
+}
+
+/**
+ * @template T = mixed
+ */
+final class TemplateWithDefaultDoesNotWork
+{
+	/**
+	 * @var I<T>
+	 */
+	public readonly I $i;
+
+	/**
+	 * @param I<T> $i
+	 */
+	public function __construct(I $i = E::E)
+	{
+		$this->i = $i;
+	}
+}