[INFO] fetching crate maybe-serde 0.2.1...
[INFO] testing maybe-serde-0.2.1 against beta-2025-10-28 for beta-1.92-2
[INFO] extracting crate maybe-serde 0.2.1 into /workspace/builds/worker-0-tc2/source
[INFO] started tweaking crates.io crate maybe-serde 0.2.1
[INFO] finished tweaking crates.io crate maybe-serde 0.2.1
[INFO] tweaked toml for crates.io crate maybe-serde 0.2.1 written to /workspace/builds/worker-0-tc2/source/Cargo.toml
[INFO] validating manifest of crates.io crate maybe-serde 0.2.1 on toolchain beta-2025-10-28
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+beta-2025-10-28" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+beta-2025-10-28" "generate-lockfile" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Updating crates.io index
[INFO] [stderr]      Locking 11 packages to latest compatible versions
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+beta-2025-10-28" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc2/source:/opt/rustwide/workdir:ro,Z" "-v" "/var/lib/crater-agent-workspace/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/var/lib/crater-agent-workspace/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "1610612736" "--user" "0:0" "--network" "none" "ghcr.io/rust-lang/crates-build-env/linux@sha256:4848fb76d95f26979359cc7e45710b1dbc8f3acb7aeedee7c460d7702230f228" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2025-10-28" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 6a759082c8199b9babb6285e1091946fd172f0d23661f2beb380d069cf47d0e7
[INFO] running `Command { std: "docker" "start" "-a" "6a759082c8199b9babb6285e1091946fd172f0d23661f2beb380d069cf47d0e7", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "6a759082c8199b9babb6285e1091946fd172f0d23661f2beb380d069cf47d0e7", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "6a759082c8199b9babb6285e1091946fd172f0d23661f2beb380d069cf47d0e7", kill_on_drop: false }`
[INFO] [stdout] 6a759082c8199b9babb6285e1091946fd172f0d23661f2beb380d069cf47d0e7
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc2/source:/opt/rustwide/workdir:ro,Z" "-v" "/var/lib/crater-agent-workspace/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/var/lib/crater-agent-workspace/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "CARGO_INCREMENTAL=0" "-e" "RUST_BACKTRACE=full" "-e" "RUSTFLAGS=--cap-lints=warn" "-e" "RUSTDOCFLAGS=--cap-lints=warn" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "1610612736" "--user" "0:0" "--network" "none" "ghcr.io/rust-lang/crates-build-env/linux@sha256:4848fb76d95f26979359cc7e45710b1dbc8f3acb7aeedee7c460d7702230f228" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2025-10-28" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] d25fc1eb9837ee7624ef1f09db85f8a6b8f5dc29db3650ae84c16af465cf463c
[INFO] running `Command { std: "docker" "start" "-a" "d25fc1eb9837ee7624ef1f09db85f8a6b8f5dc29db3650ae84c16af465cf463c", kill_on_drop: false }`
[INFO] [stderr]    Compiling serde v1.0.228
[INFO] [stderr]    Compiling maybe-serde v0.2.1 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the beta release channel
[INFO] [stdout]  --> src/lib.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(specialization)]
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
[INFO] [stdout]  --> src/lib.rs:1:12
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(specialization)]
[INFO] [stdout]   |            ^^^^^^^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
[INFO] [stdout]   = help: consider using `min_specialization` instead, which is more stable and complete
[INFO] [stdout]   = note: `#[warn(incomplete_features)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `maybe-serde` (lib) due to 1 previous error; 1 warning emitted
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] running `Command { std: "docker" "inspect" "d25fc1eb9837ee7624ef1f09db85f8a6b8f5dc29db3650ae84c16af465cf463c", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "d25fc1eb9837ee7624ef1f09db85f8a6b8f5dc29db3650ae84c16af465cf463c", kill_on_drop: false }`
[INFO] [stdout] d25fc1eb9837ee7624ef1f09db85f8a6b8f5dc29db3650ae84c16af465cf463c