[INFO] fetching crate maybe-single 0.15.0...
[INFO] testing maybe-single-0.15.0 against beta-2021-09-08 for beta-1.56-1
[INFO] extracting crate maybe-single 0.15.0 into /workspace/builds/worker-0/source
[INFO] validating manifest of crates.io crate maybe-single 0.15.0 on toolchain beta-2021-09-08
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta-2021-09-08" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking crates.io crate maybe-single 0.15.0
[INFO] finished tweaking crates.io crate maybe-single 0.15.0
[INFO] tweaked toml for crates.io crate maybe-single 0.15.0 written to /workspace/builds/worker-0/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta-2021-09-08" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta-2021-09-08" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/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" "+beta-2021-09-08" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] b1c716e920667958d23a0223e9f12ca9952b547497f0608311dc41afb5f565e6
[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" "b1c716e920667958d23a0223e9f12ca9952b547497f0608311dc41afb5f565e6", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "b1c716e920667958d23a0223e9f12ca9952b547497f0608311dc41afb5f565e6", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "b1c716e920667958d23a0223e9f12ca9952b547497f0608311dc41afb5f565e6", kill_on_drop: false }`
[INFO] [stdout] b1c716e920667958d23a0223e9f12ca9952b547497f0608311dc41afb5f565e6
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/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" "+beta-2021-09-08" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 26575c25b623da19bd0b0ed4003cb8794184f0afb3ea91e650bd3837d65a5651
[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" "26575c25b623da19bd0b0ed4003cb8794184f0afb3ea91e650bd3837d65a5651", kill_on_drop: false }`
[INFO] [stderr]    Compiling maybe-single v0.15.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: field is never read: `read_lock`
[INFO] [stdout]   --> src/blocking.rs:73:5
[INFO] [stdout]    |
[INFO] [stdout] 73 |     read_lock: Option<RwLockReadGuard<'a, ()>>,
[INFO] [stdout]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field is never read: `write_lock`
[INFO] [stdout]   --> src/blocking.rs:74:5
[INFO] [stdout]    |
[INFO] [stdout] 74 |     write_lock: Option<RwLockWriteGuard<'a, ()>>,
[INFO] [stdout]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 0.39s
[INFO] running `Command { std: "docker" "inspect" "26575c25b623da19bd0b0ed4003cb8794184f0afb3ea91e650bd3837d65a5651", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "26575c25b623da19bd0b0ed4003cb8794184f0afb3ea91e650bd3837d65a5651", kill_on_drop: false }`
[INFO] [stdout] 26575c25b623da19bd0b0ed4003cb8794184f0afb3ea91e650bd3837d65a5651
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/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" "+beta-2021-09-08" "test" "--frozen" "--no-run" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 265c818f6e12e1f70a8de7a21534a9a3191bea0ee8b7717a0fe0fcad6e391078
[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" "265c818f6e12e1f70a8de7a21534a9a3191bea0ee8b7717a0fe0fcad6e391078", kill_on_drop: false }`
[INFO] [stderr]    Compiling tokio v1.11.0
[INFO] [stdout] warning: field is never read: `read_lock`
[INFO] [stdout]   --> src/blocking.rs:73:5
[INFO] [stdout]    |
[INFO] [stdout] 73 |     read_lock: Option<RwLockReadGuard<'a, ()>>,
[INFO] [stdout]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field is never read: `write_lock`
[INFO] [stdout]   --> src/blocking.rs:74:5
[INFO] [stdout]    |
[INFO] [stdout] 74 |     write_lock: Option<RwLockWriteGuard<'a, ()>>,
[INFO] [stdout]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]    Compiling maybe-single v0.15.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: field is never read: `read_lock`
[INFO] [stdout]   --> src/blocking.rs:73:5
[INFO] [stdout]    |
[INFO] [stdout] 73 |     read_lock: Option<RwLockReadGuard<'a, ()>>,
[INFO] [stdout]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field is never read: `write_lock`
[INFO] [stdout]   --> src/blocking.rs:74:5
[INFO] [stdout]    |
[INFO] [stdout] 74 |     write_lock: Option<RwLockWriteGuard<'a, ()>>,
[INFO] [stdout]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished test [unoptimized + debuginfo] target(s) in 6.28s
[INFO] running `Command { std: "docker" "inspect" "265c818f6e12e1f70a8de7a21534a9a3191bea0ee8b7717a0fe0fcad6e391078", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "265c818f6e12e1f70a8de7a21534a9a3191bea0ee8b7717a0fe0fcad6e391078", kill_on_drop: false }`
[INFO] [stdout] 265c818f6e12e1f70a8de7a21534a9a3191bea0ee8b7717a0fe0fcad6e391078
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/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" "+beta-2021-09-08" "test" "--frozen", kill_on_drop: false }`
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] [stdout] 8e91fa764174919a49c73972e91d56b049ffd9302001b5e9ebe692b2de01a325
[INFO] running `Command { std: "docker" "start" "-a" "8e91fa764174919a49c73972e91d56b049ffd9302001b5e9ebe692b2de01a325", kill_on_drop: false }`
[INFO] [stdout] 
[INFO] [stderr] warning: field is never read: `read_lock`
[INFO] [stdout] running 2 tests
[INFO] [stderr]   --> src/blocking.rs:73:5
[INFO] [stderr]    |
[INFO] [stderr] 73 |     read_lock: Option<RwLockReadGuard<'a, ()>>,
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr]    |
[INFO] [stderr]    = note: `#[warn(dead_code)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: field is never read: `write_lock`
[INFO] [stderr]   --> src/blocking.rs:74:5
[INFO] [stderr]    |
[INFO] [stderr] 74 |     write_lock: Option<RwLockWriteGuard<'a, ()>>,
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: `maybe-single` (lib) generated 2 warnings
[INFO] [stderr] warning: `maybe-single` (lib test) generated 2 warnings (2 duplicates)
[INFO] [stderr]     Finished test [unoptimized + debuginfo] target(s) in 0.05s
[INFO] [stderr]      Running unittests (/opt/rustwide/target/debug/deps/maybe_single-7e1de0e719910ac9)
[INFO] [stdout] test blocking::test::should_execute_in_parallel ... ok
[INFO] [stderr]    Doc-tests maybe-single
[INFO] [stdout] test blocking::test::should_execute_serially ... ok
[INFO] [stdout] 
[INFO] [stdout] test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.27s
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] running 0 tests
[INFO] [stdout] 
[INFO] [stdout] test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
[INFO] [stdout] 
[INFO] running `Command { std: "docker" "inspect" "8e91fa764174919a49c73972e91d56b049ffd9302001b5e9ebe692b2de01a325", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "8e91fa764174919a49c73972e91d56b049ffd9302001b5e9ebe692b2de01a325", kill_on_drop: false }`
[INFO] [stdout] 8e91fa764174919a49c73972e91d56b049ffd9302001b5e9ebe692b2de01a325