[INFO] cloning repository https://github.com/learn-you-a-rust/references
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/learn-you-a-rust/references" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Flearn-you-a-rust%2Freferences", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Flearn-you-a-rust%2Freferences'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 6ff4ef6f42c370e58278100c0a8e74b01e4b82a9
[INFO] checking learn-you-a-rust/references against beta for pr-78714
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Flearn-you-a-rust%2Freferences" "/workspace/builds/worker-4/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-4/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/learn-you-a-rust/references on toolchain beta
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta" "read-manifest" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] started tweaking git repo https://github.com/learn-you-a-rust/references
[INFO] finished tweaking git repo https://github.com/learn-you-a-rust/references
[INFO] tweaked toml for git repo https://github.com/learn-you-a-rust/references written to /workspace/builds/worker-4/source/Cargo.toml
[INFO] crate git repo https://github.com/learn-you-a-rust/references already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/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" "rustops/crates-build-env@sha256:6eabd152ff4036248d66efda456a36cb33d24b7291b33f25f75140726c88da35" "/opt/rustwide/cargo-home/bin/cargo" "+beta" "metadata" "--no-deps" "--format-version=1", 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] 50be936a2986be82de4c00fc6154598238d53d7ddeb9e5ca88a1dd089987dbe6
[INFO] running `Command { std: "docker" "start" "-a" "50be936a2986be82de4c00fc6154598238d53d7ddeb9e5ca88a1dd089987dbe6", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "50be936a2986be82de4c00fc6154598238d53d7ddeb9e5ca88a1dd089987dbe6", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "50be936a2986be82de4c00fc6154598238d53d7ddeb9e5ca88a1dd089987dbe6", kill_on_drop: false }`
[INFO] [stdout] 50be936a2986be82de4c00fc6154598238d53d7ddeb9e5ca88a1dd089987dbe6
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/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" "rustops/crates-build-env@sha256:6eabd152ff4036248d66efda456a36cb33d24b7291b33f25f75140726c88da35" "/opt/rustwide/cargo-home/bin/cargo" "+beta" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 03042f2fe2ce605b779cdfb5e02ec5ca44a14600e0834c7bcd11b52929116e3c
[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" "03042f2fe2ce605b779cdfb5e02ec5ca44a14600e0834c7bcd11b52929116e3c", kill_on_drop: false }`
[INFO] [stderr]     Checking references v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: unused variable: `s4`
[INFO] [stdout]   --> src/main.rs:19:9
[INFO] [stdout]    |
[INFO] [stdout] 19 |     let s4 = &s1;        // <-- if this ref exists, &mut s1 refs can't be used 
[INFO] [stdout]    |         ^^ help: if this is intentional, prefix it with an underscore: `_s4`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `s2`
[INFO] [stdout]   --> src/main.rs:31:13
[INFO] [stdout]    |
[INFO] [stdout] 31 |         let s2 = &mut s1;
[INFO] [stdout]    |             ^^ help: if this is intentional, prefix it with an underscore: `_s2`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `reference_to_nothing`
[INFO] [stdout]   --> src/main.rs:45:9
[INFO] [stdout]    |
[INFO] [stdout] 45 |     let reference_to_nothing = no_dangle();
[INFO] [stdout]    |         ^^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_reference_to_nothing`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `some_string`
[INFO] [stdout]   --> src/main.rs:65:11
[INFO] [stdout]    |
[INFO] [stdout] 65 | fn change(some_string: &String) {
[INFO] [stdout]    |           ^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_some_string`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `s4`
[INFO] [stdout]   --> src/main.rs:19:9
[INFO] [stdout]    |
[INFO] [stdout] 19 |     let s4 = &s1;        // <-- if this ref exists, &mut s1 refs can't be used 
[INFO] [stdout]    |         ^^ help: if this is intentional, prefix it with an underscore: `_s4`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `s2`
[INFO] [stdout]   --> src/main.rs:31:13
[INFO] [stdout]    |
[INFO] [stdout] 31 |         let s2 = &mut s1;
[INFO] [stdout]    |             ^^ help: if this is intentional, prefix it with an underscore: `_s2`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `reference_to_nothing`
[INFO] [stdout]   --> src/main.rs:45:9
[INFO] [stdout]    |
[INFO] [stdout] 45 |     let reference_to_nothing = no_dangle();
[INFO] [stdout]    |         ^^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_reference_to_nothing`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `some_string`
[INFO] [stdout]   --> src/main.rs:65:11
[INFO] [stdout]    |
[INFO] [stdout] 65 | fn change(some_string: &String) {
[INFO] [stdout]    |           ^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_some_string`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `change`
[INFO] [stdout]   --> src/main.rs:65:4
[INFO] [stdout]    |
[INFO] [stdout] 65 | fn change(some_string: &String) {
[INFO] [stdout]    |    ^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `change`
[INFO] [stdout]   --> src/main.rs:65:4
[INFO] [stdout]    |
[INFO] [stdout] 65 | fn change(some_string: &String) {
[INFO] [stdout]    |    ^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 5 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 5 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 0.14s
[INFO] running `Command { std: "docker" "inspect" "03042f2fe2ce605b779cdfb5e02ec5ca44a14600e0834c7bcd11b52929116e3c", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "03042f2fe2ce605b779cdfb5e02ec5ca44a14600e0834c7bcd11b52929116e3c", kill_on_drop: false }`
[INFO] [stdout] 03042f2fe2ce605b779cdfb5e02ec5ca44a14600e0834c7bcd11b52929116e3c