Test that a Stringable object passed to a native string parameter fires UsedAsStringNode

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Node/UsedAsStringRuleTest.php

@@ -179,6 +179,10 @@ public function testRule(): void
 				"Used as string: 'union with string argument' ('union with string argument')",
 				137,
 			],
+			[
+				'Used as string: $obj (ExprUsedAsString\StringableObject)',
+				180,
+			],
 		]);
 	}
 

tests/PHPStan/Node/data/used-as-string.php

@@ -163,3 +163,18 @@ function passMixedArgument(): void
 {
 	takesMixed('mixed argument');
 }
+
+class StringableObject
+{
+
+	public function __toString(): string
+	{
+		return 'stringable';
+	}
+
+}
+
+function passStringableArgument(StringableObject $obj): void
+{
+	takesString($obj);
+}