quickwit-oss/quickwit · error · proc-macro compile error

structure implement serialize but no serializer defined

Error message

structure implement serialize but no serializer defined

What it means

In generate_proxy_struct, each field annotated with serde_multikey options can declare an `into` (serializer) conversion. If the struct itself implements Serialize but a serialized field has no `into` conversion defined, the macro cannot serialize that field and emits this error at the field's span.

Source

Thrown at quickwit/quickwit-macros/src/lib.rs:182

        // we are in a "normal" struct, not a tuple-struct, unwrap is fine.
        let field_name = field.ident.clone().unwrap();

        let (field_config, attrs) = parse_attributes(field.attrs, &field_name)?;
        field.attrs = attrs;

        if let Some(field_config) = field_config {
            let value = Ident::new("value", Span::call_site());
            for field in &field_config.proxy_fields {
                final_fields.push(field.clone());
            }
            match (ser, field_config.get_into(&value)) {
                (true, Some((pre_conv, in_conv))) => {
                    into_pre_conv.push(pre_conv);
                    into_in_conv.push(in_conv);
                }
                (false, None) => (),
                (true, None) => {
                    return Err(Error::new(
                        field_name.span(),
                        "structure implement serialize but no serializer defined",
                    ));
                }
                (false, Some(_)) => {
                    return Err(Error::new(
                        field_name.span(),
                        "structure doesn't implement serialize but a serializer is defined",
                    ));
                }
            }
            match (de, field_config.get_try_from(&value)) {
                (true, Some(conv)) => {
                    try_from_conv.push(conv);
                }
                (false, None) => (),
                (true, None) => {
                    return Err(Error::new(

View on GitHub (pinned to a39730c5cd)

Solutions

1. Define the serializer conversion for the field (e.g. `into = ...` / try_into mapping) in the field's serde_multikey config.
2. Or mark the field so it is not part of the serialized form (skip it) if it should not be serialized.

Example fix

// before
#[serde_multikey(
    fields(value)
)]
// after
#[serde_multikey(
    fields(value(into = into_str))
)]

// For every field in fields(...) of a Serialize struct, ensure an `into` conversion exists:
// #[serde_multikey(fields(value(into = convert_value)))]

When it happens

Trigger: The struct has a Serialize impl/derive, and #[serde_multikey(fields(...))] includes a field in the serialization path whose field config lacks an `into`/serializer conversion while that field is set for serialization.

Common situations: Adding a new field to a serialized multikey struct without adding its `into = ...` conversion; copy-pasting field configs from a deserialize-only struct.

Understand the failure class

Background: "Must pass :limit option" / "Missing required option" — required option errors explained — this error's family across 41 libraries.

Related errors

• `serde_multikey` was applied to a non Serialize/Deserialize
• `serde_multikey` was applied to a tuple-struct or an empty s
• structure doesn't implement serialize but a serializer is de
• structure implement deserialize but no deserializer defined
• structure doesn't implement deserialize but a deserializer i

AI-assisted analysis of quickwit-oss/quickwit@a39730c5cd (2026-09-08). Data as JSON: /api/errors/83616046bcc2da67. Report an issue: GitHub.