FuelLabs/fuels-rs · error

log id should be a valid u64 string

Error message

log id should be a valid u64 string

What it means

Same codegen path as the enum case, but for struct types: when a struct is a logged type, abigen! parses the log id string from the ABI into u64 to emit the Log::LOG_ID_U64 constant (packages/fuels-code-gen/src/program_bindings/custom_types/structs.rs:76). The expect fires when the id string cannot be parsed as u64.

Source

Thrown at packages/fuels-code-gen/src/program_bindings/custom_types/structs.rs:76

    struct_ident: &Ident,
    components: &Components,
    generics: &[Ident],
    no_std: bool,
    log_id: Option<&String>,
) -> TokenStream {
    let derive_default = components
        .is_empty()
        .then(|| quote!(::core::default::Default,));

    let maybe_disable_std = no_std.then(|| quote! {#[NoStd]});

    let (generics_wo_bounds, generics_w_bounds) = tokenize_generics(generics);
    let (field_names, field_types): (Vec<_>, Vec<_>) = unzip_field_names_and_types(components);
    let (phantom_fields, phantom_types) =
        components.generate_parameters_for_unused_generics(generics);

    let log_impl = log_id.map(|log_id| {
        let log_id_u64: u64 = log_id.parse::<u64>().expect("log id should be a valid u64 string");

        quote! {
            impl #generics_w_bounds ::fuels::core::codec::Log for #struct_ident #generics_wo_bounds {
                const LOG_ID: &'static str = #log_id;
                const LOG_ID_U64: u64 = #log_id_u64;
            }
        }
    });

    quote! {
        #[derive(
            Clone,
            Debug,
            Eq,
            PartialEq,
            #derive_default
            ::fuels::macros::Parameterize,
            ::fuels::macros::Tokenizable,

View on GitHub (pinned to d9a250a518)

Solutions

1. Regenerate the ABI with forc build using the toolchain matched to your fuels crate
2. Verify the loggedTypes ids are plain decimal strings parseable as u64
3. Upgrade fuels to the version matching your ABI format

Example fix

// before
"loggedTypes": [{ "id": "log-1", ... }]

// after
"loggedTypes": [{ "id": "16423", ... }]

# (shell) every loggedTypes id must round-trip through a u64
jq -e '[.loggedTypes[]?.id] | map(. == (.|tonumber|tostring)) | all' out/release/contract-abi.json

fn valid_log_id(id: &str) -> bool {
    id.parse::<u64>().is_ok()
}

When it happens

Trigger: abigen! on an ABI where the loggedTypes id attached to a struct type is not a decimal u64 string (corruption, manual edit, or forc/SDK version mismatch).

Common situations: Hand-edited ABIs; ABI files copied between projects built with different forc versions; partial rewrites of the JSON.

Related errors

• Failed to resolve log type
• log id should be a valid u64 string
• Only one `Abigen` command allowed
• Add an `Abigen(..)` command!
• is there

AI-assisted analysis of FuelLabs/fuels-rs@d9a250a518 (2026-08-16). Data as JSON: /api/errors/080b9dce227f9481. Report an issue: GitHub.