qrcode.chapril.org/vendor/wikimedia/less.php/lib/Less/Tree/Variable.php

<?php
/**
 * @private
 */
class Less_Tree_Variable extends Less_Tree {

	public $name;
	public $index;
	public $currentFileInfo;
	public $evaluating = false;
	public $type = 'Variable';

	/**
	 * @param string $name
	 */
	public function __construct( $name, $index = null, $currentFileInfo = null ) {
		$this->name = $name;
		$this->index = $index;
		$this->currentFileInfo = $currentFileInfo;
	}

	/**
	 * @param Less_Environment $env
	 * @return Less_Tree
	 * @see less-2.5.3.js#Ruleset.prototype.eval
	 */
	public function compile( $env ) {
		if ( $this->name[1] === '@' ) {
			$v = new Less_Tree_Variable( substr( $this->name, 1 ), $this->index + 1, $this->currentFileInfo );
			// While some Less_Tree nodes have no 'value', we know these can't ocurr after a variable
			// assignment (would have been a ParseError).
			// TODO: Solve better (https://phabricator.wikimedia.org/T327082).
			// @phan-suppress-next-line PhanUndeclaredProperty
			$name = '@' . $v->compile( $env )->value;
		} else {
			$name = $this->name;
		}

		if ( $this->evaluating ) {
			throw new Less_Exception_Compiler( "Recursive variable definition for " . $name, null, $this->index, $this->currentFileInfo );
		}

		$this->evaluating = true;

		foreach ( $env->frames as $frame ) {
			if ( $v = $frame->variable( $name ) ) {
				$r = $v->value->compile( $env );
				$this->evaluating = false;
				return $r;
			}
		}

		throw new Less_Exception_Compiler( "variable " . $name . " is undefined in file " . $this->currentFileInfo["filename"], null, $this->index, $this->currentFileInfo );
	}

}