Inline returned variables aren't considered used

[arichard4]

In some cases, a return statement isn't considered as using a variable, property, or closure.

<?php

class A {
	private static $cache;
	private static function ExpensiveFunction() {
		return 1;
	}

	public static function CachedCall() {
		return self::$cache ??= static::ExpensiveFunction();
	}

	public static function ReturnsVar() {
		return $x = 1;
	}

	public static function ReturnsFunc() {
		return function() { return 1; };
	}
}

A::CachedCall();
A::ReturnsVar();
A::ReturnsFunc();

../phan/build/phan.phar --dead-code-detection return.php
 dead code ████████████████████████████████████████████████████ 100% 31MB/33MB
cache.php:4 PhanWriteOnlyPrivateProperty Possibly zero read references to private property \A::$cache
cache.php:14 PhanUnusedVariable Unused definition of variable $x
cache.php:18 PhanUnreferencedClosure Possibly zero references to Closure()

This is true both for 5.2.1 and for tip of v5.

[TysonAndre]

cache.php:14 PhanUnusedVariable Unused definition of variable $x is by design.

PhanUnreferencedClosure is a different type of false positive - that issue type predates unused variable detection, and just checks if the closure is called and has a high false positive rate in general.

[arichard4]

Thanks so much, sorry for the incorrect report!