[INFO] fetching crate mech-syntax 0.0.5...
[INFO] testing mech-syntax-0.0.5 against 1.55.0 for beta-1.56-1
[INFO] extracting crate mech-syntax 0.0.5 into /workspace/builds/worker-65/source
[INFO] validating manifest of crates.io crate mech-syntax 0.0.5 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 mech-syntax 0.0.5
[INFO] finished tweaking crates.io crate mech-syntax 0.0.5
[INFO] tweaked toml for crates.io crate mech-syntax 0.0.5 written to /workspace/builds/worker-65/source/Cargo.toml
[INFO] crate crates.io crate mech-syntax 0.0.5 already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]  Downloading crates ...
[INFO] [stderr]   Downloaded static_assertions v0.3.4
[INFO] [stderr]   Downloaded lexical-core v0.6.7
[INFO] [stderr]   Downloaded rlibc v1.0.0
[INFO] [stderr]   Downloaded ahash v0.3.4
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-65/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-65/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] 82662399ec2c20f2138a71d13f2da83b30ba403b784f32f94f8d8ab89b3f653d
[INFO] running `Command { std: "docker" "start" "-a" "82662399ec2c20f2138a71d13f2da83b30ba403b784f32f94f8d8ab89b3f653d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "82662399ec2c20f2138a71d13f2da83b30ba403b784f32f94f8d8ab89b3f653d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "82662399ec2c20f2138a71d13f2da83b30ba403b784f32f94f8d8ab89b3f653d", kill_on_drop: false }`
[INFO] [stdout] 82662399ec2c20f2138a71d13f2da83b30ba403b784f32f94f8d8ab89b3f653d
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-65/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-65/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] d0c587104492960f334d1b60ad54f9de9cb23219d482b0741874ee4df56bb184
[INFO] running `Command { std: "docker" "start" "-a" "d0c587104492960f334d1b60ad54f9de9cb23219d482b0741874ee4df56bb184", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling proc-macro2 v1.0.12
[INFO] [stderr]    Compiling semver-parser v0.7.0
[INFO] [stderr]    Compiling ryu v1.0.4
[INFO] [stderr]    Compiling syn v1.0.18
[INFO] [stderr]    Compiling arrayvec v0.4.12
[INFO] [stderr]    Compiling memchr v2.3.3
[INFO] [stderr]    Compiling serde v1.0.106
[INFO] [stderr]    Compiling nodrop v0.1.14
[INFO] [stderr]    Compiling cfg-if v0.1.9
[INFO] [stderr]    Compiling static_assertions v0.3.4
[INFO] [stderr]    Compiling ahash v0.3.4
[INFO] [stderr]    Compiling hashbrown v0.7.2
[INFO] [stderr]    Compiling nom v5.1.1
[INFO] [stderr]    Compiling semver v0.9.0
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]   --> /opt/rustwide/cargo-home/registry/src/github.com-1ecc6299db9ec823/hashbrown-0.7.2/src/lib.rs:15:5
[INFO] [stdout]    |
[INFO] [stdout] 15 | /     feature(
[INFO] [stdout] 16 | |         alloc_layout_extra,
[INFO] [stdout] 17 | |         allocator_api,
[INFO] [stdout] 18 | |         ptr_offset_from,
[INFO] [stdout] ...  |
[INFO] [stdout] 22 | |         specialization,
[INFO] [stdout] 23 | |     )
[INFO] [stdout]    | |_____^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to previous error
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `hashbrown` due to 2 previous errors
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error: build failed
[INFO] running `Command { std: "docker" "inspect" "d0c587104492960f334d1b60ad54f9de9cb23219d482b0741874ee4df56bb184", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "d0c587104492960f334d1b60ad54f9de9cb23219d482b0741874ee4df56bb184", kill_on_drop: false }`
[INFO] [stdout] d0c587104492960f334d1b60ad54f9de9cb23219d482b0741874ee4df56bb184