[INFO] cloning repository https://github.com/Tandolf/semaphores
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/Tandolf/semaphores" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FTandolf%2Fsemaphores", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FTandolf%2Fsemaphores'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] e19f9d70de4243a3887f3ac3a43828feb2305ee3
[INFO] checking Tandolf/semaphores against try#afeffcd090fe6cee35c99f8b5539d74aa443fe34 for pr-140956
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FTandolf%2Fsemaphores" "/workspace/builds/worker-2-tc2/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-2-tc2/source'...
[INFO] [stderr] done.
[INFO] started tweaking git repo https://github.com/Tandolf/semaphores
[INFO] finished tweaking git repo https://github.com/Tandolf/semaphores
[INFO] tweaked toml for git repo https://github.com/Tandolf/semaphores written to /workspace/builds/worker-2-tc2/source/Cargo.toml
[INFO] validating manifest of git repo https://github.com/Tandolf/semaphores on toolchain afeffcd090fe6cee35c99f8b5539d74aa443fe34
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+afeffcd090fe6cee35c99f8b5539d74aa443fe34" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] crate git repo https://github.com/Tandolf/semaphores already has a lockfile, it will not be regenerated
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+afeffcd090fe6cee35c99f8b5539d74aa443fe34" "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-2-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/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@sha256:90999bfc7ae267e83380e433d8e61a7c072ca6729e92edbae886d3423b3a6f4c" "/opt/rustwide/cargo-home/bin/cargo" "+afeffcd090fe6cee35c99f8b5539d74aa443fe34" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] cb5de326aa02f5760c5e57988e0f032ec5a48cefdd6fa744ed95f120b1d1f40c
[INFO] running `Command { std: "docker" "start" "-a" "cb5de326aa02f5760c5e57988e0f032ec5a48cefdd6fa744ed95f120b1d1f40c", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "cb5de326aa02f5760c5e57988e0f032ec5a48cefdd6fa744ed95f120b1d1f40c", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "cb5de326aa02f5760c5e57988e0f032ec5a48cefdd6fa744ed95f120b1d1f40c", kill_on_drop: false }`
[INFO] [stdout] cb5de326aa02f5760c5e57988e0f032ec5a48cefdd6fa744ed95f120b1d1f40c
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/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" "RUSTDOCFLAGS=--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@sha256:90999bfc7ae267e83380e433d8e61a7c072ca6729e92edbae886d3423b3a6f4c" "/opt/rustwide/cargo-home/bin/cargo" "+afeffcd090fe6cee35c99f8b5539d74aa443fe34" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] b913eec6507d25da1030cc964f0189330ef040d46d2b26274207be3b30569422
[INFO] running `Command { std: "docker" "start" "-a" "b913eec6507d25da1030cc964f0189330ef040d46d2b26274207be3b30569422", kill_on_drop: false }`
[INFO] [stderr]    Compiling libc v0.2.149
[INFO] [stderr]     Checking getrandom v0.2.10
[INFO] [stderr]     Checking rand_core v0.6.4
[INFO] [stderr]     Checking rand_chacha v0.3.1
[INFO] [stderr]     Checking rand v0.8.5
[INFO] [stderr]     Checking semaphores v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] error: non-binding let on a synchronization lock
[INFO] [stdout]   --> src/multiplex.rs:34:25
[INFO] [stdout]    |
[INFO] [stdout] 34 |                     let _ = cvar.wait_while(queue.lock().unwrap(), |value| *value == 0);
[INFO] [stdout]    |                         ^ this lock is not assigned to a binding and is immediately dropped
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[deny(let_underscore_lock)]` on by default
[INFO] [stdout] help: consider binding to an unused variable to avoid immediately dropping the value
[INFO] [stdout]    |
[INFO] [stdout] 34 |                     let _unused = cvar.wait_while(queue.lock().unwrap(), |value| *value == 0);
[INFO] [stdout]    |                          ++++++
[INFO] [stdout] help: consider immediately dropping the value
[INFO] [stdout]    |
[INFO] [stdout] 34 -                     let _ = cvar.wait_while(queue.lock().unwrap(), |value| *value == 0);
[INFO] [stdout] 34 +                     drop(cvar.wait_while(queue.lock().unwrap(), |value| *value == 0));
[INFO] [stdout]    |
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `semaphores` (bin "semaphores") due to 1 previous error
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stdout] error: non-binding let on a synchronization lock
[INFO] [stdout]   --> src/multiplex.rs:34:25
[INFO] [stdout]    |
[INFO] [stdout] 34 |                     let _ = cvar.wait_while(queue.lock().unwrap(), |value| *value == 0);
[INFO] [stdout]    |                         ^ this lock is not assigned to a binding and is immediately dropped
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[deny(let_underscore_lock)]` on by default
[INFO] [stdout] help: consider binding to an unused variable to avoid immediately dropping the value
[INFO] [stdout]    |
[INFO] [stdout] 34 |                     let _unused = cvar.wait_while(queue.lock().unwrap(), |value| *value == 0);
[INFO] [stdout]    |                          ++++++
[INFO] [stdout] help: consider immediately dropping the value
[INFO] [stdout]    |
[INFO] [stdout] 34 -                     let _ = cvar.wait_while(queue.lock().unwrap(), |value| *value == 0);
[INFO] [stdout] 34 +                     drop(cvar.wait_while(queue.lock().unwrap(), |value| *value == 0));
[INFO] [stdout]    |
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `semaphores` (bin "semaphores" test) due to 1 previous error
[INFO] running `Command { std: "docker" "inspect" "b913eec6507d25da1030cc964f0189330ef040d46d2b26274207be3b30569422", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "b913eec6507d25da1030cc964f0189330ef040d46d2b26274207be3b30569422", kill_on_drop: false }`
[INFO] [stdout] b913eec6507d25da1030cc964f0189330ef040d46d2b26274207be3b30569422