You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: syscall.rs
    path of file: ./repos/aero/src/aero_proc/src
    
    the code of the file until where you have to start completion: // Copyright (C) 2021-2024 The Aero Project Developers.
//
// This file is part of The Aero Project.
//
// Aero is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Aero is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Aero. If not, see <https://www.gnu.org/licenses/>.

use proc_macro::TokenStream;
use proc_macro2::{Ident, Span};

use quote::quote;

use syn::punctuated::Punctuated;
use syn::spanned::Spanned;
use syn::{Expr, FnArg, NestedMeta, Pat, Type};

enum ArgType {
    Array(bool),     // mutable?
    Slice(bool),     // mutable?
    Pointer(bool),   // mutable?
    Reference(bool), // mutable?
    String,
    Path,
}

#[derive(Default)]
struct Config {
    no_return: bool,
}

// TODO: determine if no_return by checking the return type of the syscall function;
// if its the never type <!>.
fn parse_attribute_args(args: Vec<NestedMeta>) -> Config {
    let mut config = Config::default();

    for attribute in args {
        match attribute {
            NestedMeta::Meta(meta) => match meta {
                syn::Meta::Path(path) => {
                    if let Some(ident) = path.get_ident() {
                        match ident.to_string().as_str() {
                            "no_return" => config.no_return = true,
                            _ => emit_error!(ident.span(), "unknown attribute"),
                        }
         
    
fn process_call_args(args: &Punctuated<FnArg, syn::Token![,]>) -> Vec<Expr> {
    let mut result = Vec::new();

    for arg in args {
        if let FnArg::Typed(arg) = arg {
            if let Pat::Ident(pat) = arg.pat.as_ref() {
                let ty = &arg.ty;
                let ident = &pat.ident;

                if let Some(arg_type) = determine_arg_type(ty) {
                    let data_ident = Ident::new(&format!("{}_data", ident), Span::call_site());
                    let len_ident = Ident::new(&format!("{}_len", ident), Span::call_site());

                    match arg_type {
                        ArgType::Slice(is_mut) => {
                            let slice_expr: Expr = if is_mut {
                                syn::parse_quote!(crate::utils::validate_slice_mut(#data_ident as *mut _, #len_ident)?)
                            } else {
                                syn::parse_quote!(crate::utils::validate_slice(#data_ident as *const _, #len_ident)?)
                            };

                            result.push(slice_expr);
                        }

                        ArgType::Array(is_mut) => {
                            let array_expr: Expr = if is_mut {
                                syn::parse_quote!(crate::utils::validate_array_mut(#data_ident as *mut _)?)
                            } else {
                                unimplemented!()
                            };

                            result.push(array_expr);
                        }

                        ArgType::Pointer(is_mut) => {
                            let ptr_expr: Expr = if is_mut {
                                syn::parse_quote!(#ident as *mut _)
                            } else {
                                syn::parse_quote!(#ident as *const _)
                            };

                            result.push(ptr_expr);
                        }

                        ArgType::Reference(is_mut) => {
                            let ref_expr: Expr = if is_mut {
                                syn::parse_quote!(crate::utils::validate_mut_ptr(#ident as *mut _)?)
                            } else {
                                syn::parse_quote!(crate::utils::validate_ptr(#ident as *const _)?)
                            };

                            result.push(ref_expr);
                        }

                        ArgType::String => result.push(syn::parse_quote!(crate::utils::validate_str(#data_ident as *const _, #len_ident)?)),
                        ArgType::Path => {
                            result.push(syn::parse_quote!({
                                let string = crate::utils::validate_str(#data_ident as *const _, #len_ident)?;
                                Path::new(string)
                            }))
                        }
                    }
                } else {
                    result.push(syn::parse_quote!(crate::syscall::SysArg::from_usize(#ident)));
                }
            }
        }
    }

    result
}