lib/less/tree/call.js
function (name, args, index, currentFileInfo) {
    this.name = name;
    this.args = args;
    this.calc = name === 'calc';
    this._index = index;
    this._fileInfo = currentFileInfo;
}
function (name, args, index, currentFileInfo) {
    this.name = name;
    this.args = args;
    this.calc = name === 'calc';
    this._index = index;
    this._fileInfo = currentFileInfo;
}
A function call node.