[INFO] fetching crate ipc 0.2.0...
[INFO] documenting ipc-0.2.0 against 1.54.0 for beta-1.55-rustdoc-1
[INFO] extracting crate ipc 0.2.0 into /workspace/builds/worker-71/source
[INFO] validating manifest of crates.io crate ipc 0.2.0 on toolchain 1.54.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.54.0" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking crates.io crate ipc 0.2.0
[INFO] finished tweaking crates.io crate ipc 0.2.0
[INFO] tweaked toml for crates.io crate ipc 0.2.0 written to /workspace/builds/worker-71/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.54.0" "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" "+1.54.0" "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-71/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-71/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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+1.54.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 7efb7ed41f67402d69085ba45c5fed4ea7fbfad2a583b51f382bc24b302abc86
[INFO] running `Command { std: "docker" "start" "-a" "7efb7ed41f67402d69085ba45c5fed4ea7fbfad2a583b51f382bc24b302abc86", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "7efb7ed41f67402d69085ba45c5fed4ea7fbfad2a583b51f382bc24b302abc86", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "7efb7ed41f67402d69085ba45c5fed4ea7fbfad2a583b51f382bc24b302abc86", kill_on_drop: false }`
[INFO] [stdout] 7efb7ed41f67402d69085ba45c5fed4ea7fbfad2a583b51f382bc24b302abc86
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-71/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-71/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" "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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+1.54.0" "doc" "--frozen" "--no-deps" "--document-private-items" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] f159a87235fd50bd0bb2544de34d39921c717997330363f74f16b2f66585adce
[INFO] running `Command { std: "docker" "start" "-a" "f159a87235fd50bd0bb2544de34d39921c717997330363f74f16b2f66585adce", kill_on_drop: false }`
[INFO] [stderr]    Compiling libc v0.2.98
[INFO] [stderr]    Compiling proc-macro2 v1.0.28
[INFO] [stderr]    Compiling unicode-xid v0.2.2
[INFO] [stderr]    Compiling log v0.4.14
[INFO] [stderr]    Compiling syn v1.0.74
[INFO] [stderr]    Compiling serde v1.0.127
[INFO] [stderr]    Compiling serde_derive v1.0.127
[INFO] [stderr]     Checking futures v0.1.31
[INFO] [stderr]    Compiling num-traits v0.2.14
[INFO] [stderr]    Compiling quote v1.0.9
[INFO] [stderr]     Checking iovec v0.1.4
[INFO] [stderr]     Checking bytes v0.4.12
[INFO] [stderr]     Checking rmp v0.8.10
[INFO] [stderr]     Checking tokio-io v0.1.13
[INFO] [stderr]     Checking rmp-serde v0.13.7
[INFO] [stderr]  Documenting ipc v0.2.0 (/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(proc_macro, conservative_impl_trait, generators)]
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = help: the feature `proc_macro` has been stable since 1.29.0 and no longer requires an attribute to enable
[INFO] [stdout]   = help: the feature `conservative_impl_trait` has been stable since 1.26.0 and no longer requires an attribute to enable
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: Compilation failed, aborting rustdoc
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to 2 previous errors
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not document `ipc`
[INFO] [stderr] 
[INFO] [stderr] Caused by:
[INFO] [stderr]   process didn't exit successfully: `rustdoc --crate-type lib --crate-name ipc src/lib.rs -o /opt/rustwide/target/doc --error-format=json --json=diagnostic-rendered-ansi --document-private-items -L dependency=/opt/rustwide/target/debug/deps --extern futures=/opt/rustwide/target/debug/deps/libfutures-533cf53875604e8f.rmeta --extern libc=/opt/rustwide/target/debug/deps/liblibc-d38c567ce4ccc50e.rmeta --extern log=/opt/rustwide/target/debug/deps/liblog-325d2e3c8b888de3.rmeta --extern rmp_serde=/opt/rustwide/target/debug/deps/librmp_serde-bbc001db4ec0db1e.rmeta --extern serde=/opt/rustwide/target/debug/deps/libserde-5678c1422d6b64cb.rmeta --extern serde_derive=/opt/rustwide/target/debug/deps/libserde_derive-05e319b971c8ec6f.so --extern tokio_io=/opt/rustwide/target/debug/deps/libtokio_io-02ad5d1208724aec.rmeta --cap-lints=warn --crate-version 0.2.0` (exit status: 1)
[INFO] running `Command { std: "docker" "inspect" "f159a87235fd50bd0bb2544de34d39921c717997330363f74f16b2f66585adce", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "f159a87235fd50bd0bb2544de34d39921c717997330363f74f16b2f66585adce", kill_on_drop: false }`
[INFO] [stdout] f159a87235fd50bd0bb2544de34d39921c717997330363f74f16b2f66585adce
