lib/less/parser/parser.js
function () {
                var selectors, rules, debugInfo;

                parserInput.save();

                if (context.dumpLineNumbers) {
                    debugInfo = getDebugInfo(parserInput.i);
                }

                selectors = this.selectors();

                if (selectors && (rules = this.block())) {
                    parserInput.forget();
                    var ruleset = new(tree.Ruleset)(selectors, rules, context.strictImports);
                    if (context.dumpLineNumbers) {
                        ruleset.debugInfo = debugInfo;
                    }
                    return ruleset;
                } else {
                    parserInput.restore();
                }
            }
function () {
                var selectors, rules, debugInfo;

                parserInput.save();

                if (context.dumpLineNumbers) {
                    debugInfo = getDebugInfo(parserInput.i);
                }

                selectors = this.selectors();

                if (selectors && (rules = this.block())) {
                    parserInput.forget();
                    var ruleset = new(tree.Ruleset)(selectors, rules, context.strictImports);
                    if (context.dumpLineNumbers) {
                        ruleset.debugInfo = debugInfo;
                    }
                    return ruleset;
                } else {
                    parserInput.restore();
                }
            }
div, .class, body > p {...}