rust-lang/cargo · error · anyhow::Error

{fields} {are} not allowed in embedded manifests

Error message

{fields} {are} not allowed in embedded manifests

What it means

Thrown at src/workspace/parser/mod.rs:1503 when parsing an embedded (single-file) manifest. Embedded manifests are restricted and cannot carry package fields that imply target discovery, native linking, or workspace membership: `workspace`, `build`, `metabuild`, `links`, `autolib`, `autobins`, `autoexamples`, `autotests`, `autobenches`, and `default-run`. Any present field is collected and reported (with correct is/are agreement).

Source

Thrown at src/workspace/parser/mod.rs:1503

                ("`package.autobins`", autobins.is_some()),
                ("`package.autoexamples`", autoexamples.is_some()),
                ("`package.autotests`", autotests.is_some()),
                ("`package.autobenches`", autobenches.is_some()),
                ("`package.default-run`", default_run.is_some()),
            ]);
        }
        let invalid_fields = invalid_fields
            .into_iter()
            .filter_map(|(name, invalid)| invalid.then_some(name))
            .collect::<Vec<_>>();
        if !invalid_fields.is_empty() {
            let fields = invalid_fields.join(", ");
            let are = if invalid_fields.len() == 1 {
                "is"
            } else {
                "are"
            };
            anyhow::bail!("{fields} {are} not allowed in embedded manifests")
        }
    }

    let resolve_behavior = match (
        normalized_package.resolver.as_ref(),
        normalized_toml
            .workspace
            .as_ref()
            .and_then(|ws| ws.resolver.as_ref()),
    ) {
        (None, None) => None,
        (Some(s), None) | (None, Some(s)) => Some(ResolveBehavior::from_manifest(s)?),
        (Some(_), Some(_)) => {
            bail!("cannot specify `resolver` field in both `[workspace]` and `[package]`")
        }
    };

    // If we have no lib at all, use the inferred lib, if available.

View on GitHub (pinned to 0e07a15537)

Solutions

1. Remove the disallowed field(s) from the script's frontmatter `[package]` table.
2. If you need `links`/`build`/workspace features, convert the script into a normal multi-file crate with a `Cargo.toml`.

Example fix

# before (script frontmatter)
[package]
name = "demo"
links = "foo"
# after
[package]
name = "demo"

const FORBIDDEN: &[&str] = &["workspace","build","metabuild","links","autolib",
    "autobins","autoexamples","autotests","autobenches","default-run"];
if is_embedded {
    if let Some(pkg) = doc.get("package").and_then(|i| i.as_table_like()) {
        for f in FORBIDDEN {
            if pkg.contains_key(*f) { return Err(format!("{f} not allowed in embedded manifest")); }
        }
    }
}

When it happens

Trigger: A `.rs` cargo script whose frontmatter `[package]` table includes e.g. `links = "foo"`, `build = "build.rs"`, `default-run = "x"`, or `autobins = false`.

Common situations: Trying to reuse a regular crate's `[package]` table inside a script file; LLM-generated frontmatter; misunderstanding embedded-manifest limits.

Related errors

• parsing `{}` requires `-Zscript`
• the manifest-path must be a path to a Cargo.toml or script f
• the manifest-path must be a path to a Cargo.toml file: `{}`
• embedded manifest `{}` requires `-Zscript`
• parsing `{}` requires `-Zscript`

AI-assisted analysis of rust-lang/cargo@0e07a15537 (2026-08-06). Data as JSON: /data/errors/51fe6b79aecc5d32.json. Report an issue: GitHub.