Latte\PhpWriter::validateTokens PHP Method

    public function validateTokens(MacroTokens $tokens)
    {
        $deprecatedVars = array_flip(['$template', '$_b', '$_l', '$_g', '$_args', '$_fi', '$_control', '$_presenter', '$_form', '$_input', '$_label', '$_snippetMode']);
        $brackets = [];
        $pos = $tokens->position;
        while ($tokens->nextToken()) {
            if ($tokens->isCurrent('?>')) {
                throw new CompileException('Forbidden ?> inside macro');
            } elseif ($tokens->isCurrent($tokens::T_VARIABLE) && isset($deprecatedVars[$tokens->currentValue()])) {
                trigger_error("Variable {$tokens->currentValue()} is deprecated.", E_USER_DEPRECATED);
            } elseif ($tokens->isCurrent($tokens::T_SYMBOL) && !$tokens->isPrev('::') && !$tokens->isNext('::') && !$tokens->isPrev('->') && !$tokens->isNext('\\') && preg_match('#^[A-Z0-9]{3,}$#', $val = $tokens->currentValue())) {
                trigger_error("Replace literal {$val} with constant('{$val}')", E_USER_DEPRECATED);
            } elseif ($tokens->isCurrent('(', '[', '{')) {
                static $counterpart = ['(' => ')', '[' => ']', '{' => '}'];
                $brackets[] = $counterpart[$tokens->currentValue()];
            } elseif ($tokens->isCurrent(')', ']', '}') && $tokens->currentValue() !== array_pop($brackets)) {
                throw new CompileException('Unexpected ' . $tokens->currentValue());
            } elseif ($tokens->isCurrent('function', 'class', 'interface', 'trait') && $tokens->isNext($tokens::T_SYMBOL, '&') || $tokens->isCurrent('return', 'yield') && !$brackets) {
                throw new CompileException("Forbidden keyword '{$tokens->currentValue()}' inside macro.");
            }
        }
        if ($brackets) {
            throw new CompileException('Missing ' . array_pop($brackets));
        }
        $tokens->position = $pos;
    }