code: func matchSimpleCall(expr syntax.Expr) (fn []string, args []syntax.Expr) {
  	call, ok := expr.(*syntax.CallExpr)
  	if !ok {
  		return nil, nil
  	}
  	if fn = matchRefPath(call.Fn); len(fn) == 0 {
  		return nil, nil
  	}
  	return fn, call.Args
  }
docs: // matchSimpleCall matches an <Expr> to <Ident>(.<Ident>)*(<Expr>*), returning
  // them.