[INFO] fetching crate phlow 2.0.1...
[INFO] testing phlow-2.0.1 against 1.90.0 for beta-1.91-3
[INFO] extracting crate phlow 2.0.1 into /workspace/builds/worker-5-tc1/source
[INFO] started tweaking crates.io crate phlow 2.0.1
[INFO] finished tweaking crates.io crate phlow 2.0.1
[INFO] tweaked toml for crates.io crate phlow 2.0.1 written to /workspace/builds/worker-5-tc1/source/Cargo.toml
[INFO] validating manifest of crates.io crate phlow 2.0.1 on toolchain 1.90.0
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+1.90.0" "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" "+1.90.0" "generate-lockfile" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Updating crates.io index
[INFO] [stderr]      Locking 63 packages to latest compatible versions
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+1.90.0" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]  Downloading crates ...
[INFO] [stderr]   Downloaded inventory v0.3.21
[INFO] [stderr]   Downloaded rust-format v0.3.4
[INFO] [stderr]   Downloaded phlow-derive v2.0.0
[INFO] [stderr]   Downloaded typetag v0.2.21
[INFO] [stderr]   Downloaded parking_lot_core v0.9.11
[INFO] [stderr]   Downloaded parking_lot v0.12.4
[INFO] [stderr]   Downloaded blob-uuid v0.5.0
[INFO] [stderr]   Downloaded typeid v1.0.3
[INFO] [stderr]   Downloaded typetag-impl v0.2.21
[INFO] [stderr]   Downloaded unique_id v0.1.7
[INFO] [stderr]   Downloaded erased-serde v0.4.8
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-5-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-5-tc1/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:e90291280db7d1fac5b66fc6dad9f9662629e7365a55743daf9bdf73ebc4ea79" "/opt/rustwide/cargo-home/bin/cargo" "+1.90.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 6bb7bf43c05f9409bea2ac070b673a3f0516eeeae3df2b4bcc874eb2f1c24f46
[INFO] running `Command { std: "docker" "start" "-a" "6bb7bf43c05f9409bea2ac070b673a3f0516eeeae3df2b4bcc874eb2f1c24f46", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "6bb7bf43c05f9409bea2ac070b673a3f0516eeeae3df2b4bcc874eb2f1c24f46", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "6bb7bf43c05f9409bea2ac070b673a3f0516eeeae3df2b4bcc874eb2f1c24f46", kill_on_drop: false }`
[INFO] [stdout] 6bb7bf43c05f9409bea2ac070b673a3f0516eeeae3df2b4bcc874eb2f1c24f46
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-5-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-5-tc1/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:e90291280db7d1fac5b66fc6dad9f9662629e7365a55743daf9bdf73ebc4ea79" "/opt/rustwide/cargo-home/bin/cargo" "+1.90.0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] e4d0b474bbdc4b8d429723513df25116996d96aaf519ea83e9c383635d5ee49a
[INFO] running `Command { std: "docker" "start" "-a" "e4d0b474bbdc4b8d429723513df25116996d96aaf519ea83e9c383635d5ee49a", kill_on_drop: false }`
[INFO] [stderr]    Compiling proc-macro2 v1.0.101
[INFO] [stderr]    Compiling unicode-ident v1.0.19
[INFO] [stderr]    Compiling quote v1.0.41
[INFO] [stderr]    Compiling autocfg v1.5.0
[INFO] [stderr]    Compiling parking_lot_core v0.9.11
[INFO] [stderr]    Compiling pin-utils v0.1.0
[INFO] [stderr]    Compiling scopeguard v1.2.0
[INFO] [stderr]    Compiling pin-project-lite v0.2.16
[INFO] [stderr]    Compiling futures-task v0.3.31
[INFO] [stderr]    Compiling smallvec v1.15.1
[INFO] [stderr]    Compiling futures-core v0.3.31
[INFO] [stderr]    Compiling slab v0.4.11
[INFO] [stderr]    Compiling log v0.4.28
[INFO] [stderr]    Compiling lock_api v0.4.13
[INFO] [stderr]    Compiling parking_lot v0.12.4
[INFO] [stderr]    Compiling rust-format v0.3.4
[INFO] [stderr]    Compiling syn v2.0.106
[INFO] [stderr]    Compiling futures-macro v0.3.31
[INFO] [stderr]    Compiling phlow-derive v2.0.0
[INFO] [stderr]    Compiling futures-util v0.3.31
[INFO] [stderr]    Compiling futures-executor v0.3.31
[INFO] [stderr]    Compiling phlow v2.0.1 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]  --> src/lib.rs:4:35
[INFO] [stdout]   |
[INFO] [stdout] 4 | #![cfg_attr(feature = "printing", feature(specialization))]
[INFO] [stdout]   |                                   ^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `phlow` (lib) due to 1 previous error
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] running `Command { std: "docker" "inspect" "e4d0b474bbdc4b8d429723513df25116996d96aaf519ea83e9c383635d5ee49a", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "e4d0b474bbdc4b8d429723513df25116996d96aaf519ea83e9c383635d5ee49a", kill_on_drop: false }`
[INFO] [stdout] e4d0b474bbdc4b8d429723513df25116996d96aaf519ea83e9c383635d5ee49a