[INFO] fetching crate async-option 0.1.1...
[INFO] checking async-option-0.1.1 against master#dfd7b8d03fb93d0e03147d28b3be6d93260fa94d for pr-87050
[INFO] extracting crate async-option 0.1.1 into /workspace/builds/worker-3/source
[INFO] validating manifest of crates.io crate async-option 0.1.1 on toolchain dfd7b8d03fb93d0e03147d28b3be6d93260fa94d
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+dfd7b8d03fb93d0e03147d28b3be6d93260fa94d" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking crates.io crate async-option 0.1.1
[INFO] finished tweaking crates.io crate async-option 0.1.1
[INFO] tweaked toml for crates.io crate async-option 0.1.1 written to /workspace/builds/worker-3/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+dfd7b8d03fb93d0e03147d28b3be6d93260fa94d" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+dfd7b8d03fb93d0e03147d28b3be6d93260fa94d" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]  Downloading crates ...
[INFO] [stderr]   Downloaded tokio-mock-task v0.1.1
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-3/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-3/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" "+dfd7b8d03fb93d0e03147d28b3be6d93260fa94d" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 634cd76d268f76353488c622b060dda7cd5a96930bab8316c38726eeeff521f5
[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" "634cd76d268f76353488c622b060dda7cd5a96930bab8316c38726eeeff521f5", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "634cd76d268f76353488c622b060dda7cd5a96930bab8316c38726eeeff521f5", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "634cd76d268f76353488c622b060dda7cd5a96930bab8316c38726eeeff521f5", kill_on_drop: false }`
[INFO] [stdout] 634cd76d268f76353488c622b060dda7cd5a96930bab8316c38726eeeff521f5
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-3/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-3/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=forbid" "-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" "+dfd7b8d03fb93d0e03147d28b3be6d93260fa94d" "check" "--frozen" "--all" "--all-targets" "--message-format=json", 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] 2af2431868bb321d1cf815687e05f02b68e4093e28b148a9c787f399eb0d0ecb
[INFO] running `Command { std: "docker" "start" "-a" "2af2431868bb321d1cf815687e05f02b68e4093e28b148a9c787f399eb0d0ecb", kill_on_drop: false }`
[INFO] [stderr]    Compiling maybe-uninit v2.0.0
[INFO] [stderr]     Checking futures v0.1.31
[INFO] [stderr]    Compiling semver-parser v0.7.0
[INFO] [stderr]    Compiling log v0.4.14
[INFO] [stderr]    Compiling crossbeam-utils v0.7.2
[INFO] [stderr]    Compiling memoffset v0.5.6
[INFO] [stderr]    Compiling crossbeam-epoch v0.8.2
[INFO] [stderr]     Checking lock_api v0.3.4
[INFO] [stderr]     Checking bytes v0.4.12
[INFO] [stderr]    Compiling semver v0.9.0
[INFO] [stderr]     Checking smallvec v0.6.14
[INFO] [stderr]    Compiling rustc_version v0.2.3
[INFO] [stderr]     Checking mio v0.6.23
[INFO] [stderr]    Compiling parking_lot_core v0.6.2
[INFO] [stderr]    Compiling parking_lot v0.9.0
[INFO] [stderr]     Checking crossbeam-queue v0.2.3
[INFO] [stderr]     Checking mio-uds v0.6.8
[INFO] [stderr]     Checking crossbeam-deque v0.7.3
[INFO] [stderr]     Checking tokio-executor v0.1.10
[INFO] [stderr]     Checking tokio-io v0.1.13
[INFO] [stderr]     Checking tokio-sync v0.1.8
[INFO] [stderr]     Checking tokio-mock-task v0.1.1
[INFO] [stderr]     Checking tokio-threadpool v0.1.18
[INFO] [stderr]     Checking tokio-timer v0.2.13
[INFO] [stderr]     Checking tokio-current-thread v0.1.7
[INFO] [stderr]     Checking async-option v0.1.1 (/opt/rustwide/workdir)
[INFO] [stderr]     Checking tokio-reactor v0.1.12
[INFO] [stderr]     Checking tokio-codec v0.1.2
[INFO] [stdout] warning: unused return value of `std::mem::replace` that must be used
[INFO] [stdout]   --> src/lib.rs:96:17
[INFO] [stdout]    |
[INFO] [stdout] 96 |                 mem::replace(self, CellValue::Fin(None));
[INFO] [stdout]    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_must_use)]` on by default
[INFO] [stdout]    = note: if you don't need the old value, you can just assign the new value directly
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 1 warning emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Checking tokio-uds v0.2.7
[INFO] [stderr]     Checking tokio-udp v0.1.6
[INFO] [stderr]     Checking tokio-tcp v0.1.4
[INFO] [stderr]     Checking tokio-fs v0.1.7
[INFO] [stderr]     Checking tokio v0.1.22
[INFO] [stdout] error: unused return value of `std::mem::replace` that must be used
[INFO] [stdout]   --> src/lib.rs:96:17
[INFO] [stdout]    |
[INFO] [stdout] 96 |                 mem::replace(self, CellValue::Fin(None));
[INFO] [stdout]    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout] note: the lint level is defined here
[INFO] [stdout]   --> src/lib.rs:26:24
[INFO] [stdout]    |
[INFO] [stdout] 26 | #![cfg_attr(test, deny(warnings))]
[INFO] [stdout]    |                        ^^^^^^^^
[INFO] [stdout]    = note: `#[deny(unused_must_use)]` implied by `#[deny(warnings)]`
[INFO] [stdout]    = note: if you don't need the old value, you can just assign the new value directly
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to previous error
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `async-option`
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `Command { std: "docker" "inspect" "2af2431868bb321d1cf815687e05f02b68e4093e28b148a9c787f399eb0d0ecb", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "2af2431868bb321d1cf815687e05f02b68e4093e28b148a9c787f399eb0d0ecb", kill_on_drop: false }`
[INFO] [stdout] 2af2431868bb321d1cf815687e05f02b68e4093e28b148a9c787f399eb0d0ecb