[INFO] fetching crate maybe-serde 0.2.1...
[INFO] checking maybe-serde-0.2.1 against try#6f8a6450478f69b8510c8976ab6c2a70b3b0e47c for pr-84920
[INFO] extracting crate maybe-serde 0.2.1 into /workspace/builds/worker-8/source
[INFO] validating manifest of crates.io crate maybe-serde 0.2.1 on toolchain 6f8a6450478f69b8510c8976ab6c2a70b3b0e47c
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+6f8a6450478f69b8510c8976ab6c2a70b3b0e47c" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[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-8/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+6f8a6450478f69b8510c8976ab6c2a70b3b0e47c" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+6f8a6450478f69b8510c8976ab6c2a70b3b0e47c" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/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@sha256:20528e8c29e4536546f0102ce88568b16ea7538393a33fcca951030f7af10457" "/opt/rustwide/cargo-home/bin/cargo" "+6f8a6450478f69b8510c8976ab6c2a70b3b0e47c" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] e612a9aa5b69be9dcaf57b9e4370a9c49ce413d51ad124dddab62a755fdd5c9a
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] running `Command { std: "docker" "start" "-a" "e612a9aa5b69be9dcaf57b9e4370a9c49ce413d51ad124dddab62a755fdd5c9a", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "e612a9aa5b69be9dcaf57b9e4370a9c49ce413d51ad124dddab62a755fdd5c9a", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "e612a9aa5b69be9dcaf57b9e4370a9c49ce413d51ad124dddab62a755fdd5c9a", kill_on_drop: false }`
[INFO] [stdout] e612a9aa5b69be9dcaf57b9e4370a9c49ce413d51ad124dddab62a755fdd5c9a
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/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=forbid" "-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@sha256:20528e8c29e4536546f0102ce88568b16ea7538393a33fcca951030f7af10457" "/opt/rustwide/cargo-home/bin/cargo" "+6f8a6450478f69b8510c8976ab6c2a70b3b0e47c" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 751372b7593e269940943444ee76e9c83949243849233adbc665449742224dc7
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] running `Command { std: "docker" "start" "-a" "751372b7593e269940943444ee76e9c83949243849233adbc665449742224dc7", kill_on_drop: false }`
[INFO] [stderr]    Compiling proc-macro2 v1.0.26
[INFO] [stderr]    Compiling unicode-xid v0.2.2
[INFO] [stderr]    Compiling serde v1.0.125
[INFO] [stderr]    Compiling serde_json v1.0.64
[INFO] [stderr]    Compiling serde_derive v1.0.125
[INFO] [stderr]     Checking itoa v0.4.7
[INFO] [stderr]    Compiling quote v1.0.9
[INFO] [stderr]    Compiling syn v1.0.72
[INFO] [stderr]     Checking maybe-serde v0.2.1 (/opt/rustwide/workdir)
[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: `#[warn(incomplete_features)]` on by default
[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] 
[INFO] [stdout] 
[INFO] [stdout] warning: 1 warning emitted
[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: `#[warn(incomplete_features)]` on by default
[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] 
[INFO] [stdout] 
[INFO] [stdout] warning: 1 warning emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 23.35s
[INFO] running `Command { std: "docker" "inspect" "751372b7593e269940943444ee76e9c83949243849233adbc665449742224dc7", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "751372b7593e269940943444ee76e9c83949243849233adbc665449742224dc7", kill_on_drop: false }`
[INFO] [stdout] 751372b7593e269940943444ee76e9c83949243849233adbc665449742224dc7