report.rs

use quote::quote;
use syn::{spanned::Spanned, Item};

pub fn body(
    _attr: proc_macro::TokenStream,
    item: proc_macro::TokenStream,
) -> syn::Result<proc_macro2::TokenStream> {
    let item = syn::parse::<Item>(item)?;

    match item {
        Item::Fn(f) => {
            let syn::ItemFn {
                attrs,
                vis,
                sig,
                block,
            } = f;

            let syn::Signature {
                constness,
                asyncness,
                unsafety,
                abi,
                fn_token,
                ident,
                generics,
                paren_token: _,
                inputs,
                variadic,
                output,
            } = sig;

            let output = match output {
                syn::ReturnType::Default => quote! {},
                syn::ReturnType::Type(_, ty) => {
                    if cfg!(feature = "rust_1_61") {
                        quote! {
                          -> ::snafu::Report<<#ty as ::snafu::__InternalExtractErrorType>::Err>
                        }
                    } else {
                        quote! {
                          -> ::core::result::Result<(), snafu::Report<<#ty as ::snafu::__InternalExtractErrorType>::Err>>
                        }
                    }
                }
            };

            Ok(quote! {
                #(#attrs)*
                #vis
                #constness
                #asyncness
                #unsafety
                #abi
                #fn_token
                #ident
                #generics
                (#inputs #variadic)
                #output
                {
                    snafu::Report::capture(|| #block)
                }
            })
        }
        _ => Err(syn::Error::new(
            item.span(),
            "`#[snafu::report]` may only be used on functions",
        )),
    }
}