[INFO] fetching crate kf-protocol-core 0.1.2...
[INFO] testing kf-protocol-core-0.1.2 against 1.55.0 for beta-1.56-1
[INFO] extracting crate kf-protocol-core 0.1.2 into /workspace/builds/worker-37/source
[INFO] validating manifest of crates.io crate kf-protocol-core 0.1.2 on toolchain 1.55.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking crates.io crate kf-protocol-core 0.1.2
[INFO] finished tweaking crates.io crate kf-protocol-core 0.1.2
[INFO] tweaked toml for crates.io crate kf-protocol-core 0.1.2 written to /workspace/builds/worker-37/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "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" "+1.55.0" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-37/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-37/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:a89201d6b5b9fd45c15d5952ece0a0129e7e80cb26ec023fd59cf09bc26f1604" "/opt/rustwide/cargo-home/bin/cargo" "+1.55.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 614a6e8e6c2a2c3cf5f6229d58919a9c9e4d9724afcb7bdf48a4a4a85c15d6c5
[INFO] running `Command { std: "docker" "start" "-a" "614a6e8e6c2a2c3cf5f6229d58919a9c9e4d9724afcb7bdf48a4a4a85c15d6c5", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "614a6e8e6c2a2c3cf5f6229d58919a9c9e4d9724afcb7bdf48a4a4a85c15d6c5", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "614a6e8e6c2a2c3cf5f6229d58919a9c9e4d9724afcb7bdf48a4a4a85c15d6c5", kill_on_drop: false }`
[INFO] [stdout] 614a6e8e6c2a2c3cf5f6229d58919a9c9e4d9724afcb7bdf48a4a4a85c15d6c5
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-37/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-37/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" "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:a89201d6b5b9fd45c15d5952ece0a0129e7e80cb26ec023fd59cf09bc26f1604" "/opt/rustwide/cargo-home/bin/cargo" "+1.55.0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 3fb6e27d55eab3e7362dc35694dc9e5a4a79519a816b1f367c42ebe17595bb5d
[INFO] running `Command { std: "docker" "start" "-a" "3fb6e27d55eab3e7362dc35694dc9e5a4a79519a816b1f367c42ebe17595bb5d", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling proc-macro2 v1.0.29
[INFO] [stderr]    Compiling proc-macro2 v0.4.30
[INFO] [stderr]    Compiling syn v1.0.76
[INFO] [stderr]    Compiling unicode-xid v0.1.0
[INFO] [stderr]    Compiling syn v0.15.44
[INFO] [stderr]    Compiling serde_derive v1.0.130
[INFO] [stderr]    Compiling log v0.4.14
[INFO] [stderr]    Compiling num-derive v0.2.5
[INFO] [stderr]    Compiling serde v1.0.130
[INFO] [stderr]    Compiling bytes v0.5.6
[INFO] [stderr]    Compiling quote v1.0.9
[INFO] [stderr]    Compiling quote v0.6.13
[INFO] [stderr]    Compiling kf-protocol-core v0.1.2 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable 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: `#[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] error: aborting due to previous error; 1 warning emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `kf-protocol-core` due to 2 previous errors; 1 warning emitted
[INFO] running `Command { std: "docker" "inspect" "3fb6e27d55eab3e7362dc35694dc9e5a4a79519a816b1f367c42ebe17595bb5d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "3fb6e27d55eab3e7362dc35694dc9e5a4a79519a816b1f367c42ebe17595bb5d", kill_on_drop: false }`
[INFO] [stdout] 3fb6e27d55eab3e7362dc35694dc9e5a4a79519a816b1f367c42ebe17595bb5d