[INFO] updating cached repository https://github.com/arashout/rust_linkedlist
[INFO] running `"git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "-c" "remote.origin.fetch=refs/heads/*:refs/heads/*" "fetch" "origin" "--force" "--prune"`
[INFO] running `"git" "rev-parse" "HEAD"`
[INFO] [stdout] 1e6015ad0ec7684f3091ed0f40001734934354c9
[INFO] checking arashout/rust_linkedlist against master#2748a9fd93dd1a00a4521f4f16de5befbf77f6cd for pr-62262-1
[INFO] running `"git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Farashout%2Frust_linkedlist" "/workspace/builds/worker-2/source"`
[INFO] [stderr] Cloning into '/workspace/builds/worker-2/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/arashout/rust_linkedlist on toolchain 2748a9fd93dd1a00a4521f4f16de5befbf77f6cd
[INFO] running `"/workspace/cargo-home/bin/cargo" "+2748a9fd93dd1a00a4521f4f16de5befbf77f6cd" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] started tweaking git repo https://github.com/arashout/rust_linkedlist
[INFO] finished tweaking git repo https://github.com/arashout/rust_linkedlist
[INFO] tweaked toml for git repo https://github.com/arashout/rust_linkedlist written to /workspace/builds/worker-2/source/Cargo.toml
[INFO] crate git repo https://github.com/arashout/rust_linkedlist already has a lockfile, it will not be regenerated
[INFO] running `"/workspace/cargo-home/bin/cargo" "+2748a9fd93dd1a00a4521f4f16de5befbf77f6cd" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] running `"docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/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" "MAP_USER_ID=0" "-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" "--network" "none" "rustops/crates-build-env" "/opt/rustwide/cargo-home/bin/cargo" "+2748a9fd93dd1a00a4521f4f16de5befbf77f6cd" "check" "--frozen" "--all" "--all-targets"`
[INFO] [stdout] 7e32699b0ab19ab463078e0fa044accd774cb097e7861ea0b01b58a89e4f58aa
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] running `"docker" "start" "-a" "7e32699b0ab19ab463078e0fa044accd774cb097e7861ea0b01b58a89e4f58aa"`
[INFO] [stderr]     Checking linkedlist v0.1.0 (/opt/rustwide/workdir)
[INFO] [stderr] warning: unused variable: `old_tail`
[INFO] [stderr]   --> src/fourth.rs:67:18
[INFO] [stderr]    |
[INFO] [stderr] 67 |             Some(old_tail) => {
[INFO] [stderr]    |                  ^^^^^^^^ help: consider prefixing with an underscore: `_old_tail`
[INFO] [stderr]    |
[INFO] [stderr]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: variant is never constructed: `More`
[INFO] [stderr]   --> src/first.rs:11:5
[INFO] [stderr]    |
[INFO] [stderr] 11 |     More(Box<Node>),
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^
[INFO] [stderr]    |
[INFO] [stderr]    = note: `#[warn(dead_code)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `new`
[INFO] [stderr]   --> src/first.rs:21:5
[INFO] [stderr]    |
[INFO] [stderr] 21 |     pub fn new()-> Self {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `push`
[INFO] [stderr]   --> src/first.rs:25:5
[INFO] [stderr]    |
[INFO] [stderr] 25 |     pub fn push(&mut self, elem: i32) {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `pop`
[INFO] [stderr]   --> src/first.rs:33:5
[INFO] [stderr]    |
[INFO] [stderr] 33 |     pub fn pop(&mut self) -> Option<i32> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `new`
[INFO] [stderr]   --> src/second.rs:13:5
[INFO] [stderr]    |
[INFO] [stderr] 13 |     pub fn new() -> Self {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `push`
[INFO] [stderr]   --> src/second.rs:17:5
[INFO] [stderr]    |
[INFO] [stderr] 17 |     pub fn push(&mut self, elem: T) {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `peek`
[INFO] [stderr]   --> src/second.rs:33:5
[INFO] [stderr]    |
[INFO] [stderr] 33 |     pub fn peek(&self) -> Option<&T> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `peek_mut`
[INFO] [stderr]   --> src/second.rs:37:5
[INFO] [stderr]    |
[INFO] [stderr] 37 |     pub fn peek_mut(&mut self) -> Option<&mut T> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `into_iter`
[INFO] [stderr]   --> src/second.rs:52:5
[INFO] [stderr]    |
[INFO] [stderr] 52 |     pub fn into_iter(self) -> IntoIter<T> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `iter`
[INFO] [stderr]   --> src/second.rs:70:5
[INFO] [stderr]    |
[INFO] [stderr] 70 |     pub fn iter<'a>(&'a self) -> Iter<'a, T> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `iter_mut`
[INFO] [stderr]   --> src/second.rs:92:5
[INFO] [stderr]    |
[INFO] [stderr] 92 |     pub fn iter_mut(&mut self) -> IterMut<'_, T> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `new`
[INFO] [stderr]   --> src/third.rs:15:5
[INFO] [stderr]    |
[INFO] [stderr] 15 |     pub fn new() -> Self {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `append`
[INFO] [stderr]   --> src/third.rs:18:5
[INFO] [stderr]    |
[INFO] [stderr] 18 |     pub fn append(&self, elem: T) -> List<T> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `tail`
[INFO] [stderr]   --> src/third.rs:26:5
[INFO] [stderr]    |
[INFO] [stderr] 26 |     pub fn tail(&self) -> List<T> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `head`
[INFO] [stderr]   --> src/third.rs:31:5
[INFO] [stderr]    |
[INFO] [stderr] 31 |     pub fn head(&self) -> Option<&T> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `iter`
[INFO] [stderr]   --> src/third.rs:41:5
[INFO] [stderr]    |
[INFO] [stderr] 41 |     pub fn iter(&self) -> Iter<'_, T> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `new`
[INFO] [stderr]   --> src/fourth.rs:18:5
[INFO] [stderr]    |
[INFO] [stderr] 18 |     fn new(elem: T) -> Rc<RefCell<Self>> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `new`
[INFO] [stderr]   --> src/fourth.rs:28:5
[INFO] [stderr]    |
[INFO] [stderr] 28 |     pub fn new() -> Self {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `push_front`
[INFO] [stderr]   --> src/fourth.rs:34:5
[INFO] [stderr]    |
[INFO] [stderr] 34 |     pub fn push_front(&mut self, elem: T) {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `push_back`
[INFO] [stderr]   --> src/fourth.rs:64:5
[INFO] [stderr]    |
[INFO] [stderr] 64 |     pub fn push_back(&mut self, elem: T) {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `peek_front`
[INFO] [stderr]   --> src/fourth.rs:76:5
[INFO] [stderr]    |
[INFO] [stderr] 76 |     pub fn peek_front(&self) -> Option<Ref<T>> {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `old_tail`
[INFO] [stderr]   --> src/fourth.rs:67:18
[INFO] [stderr]    |
[INFO] [stderr] 67 |             Some(old_tail) => {
[INFO] [stderr]    |                  ^^^^^^^^ help: consider prefixing with an underscore: `_old_tail`
[INFO] [stderr]    |
[INFO] [stderr]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: method is never used: `push_back`
[INFO] [stderr]   --> src/fourth.rs:64:5
[INFO] [stderr]    |
[INFO] [stderr] 64 |     pub fn push_back(&mut self, elem: T) {
[INFO] [stderr]    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr]    |
[INFO] [stderr]    = note: `#[warn(dead_code)]` on by default
[INFO] [stderr] 
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 1.06s
[INFO] running `"docker" "inspect" "7e32699b0ab19ab463078e0fa044accd774cb097e7861ea0b01b58a89e4f58aa"`
[INFO] running `"docker" "rm" "-f" "7e32699b0ab19ab463078e0fa044accd774cb097e7861ea0b01b58a89e4f58aa"`
[INFO] [stdout] 7e32699b0ab19ab463078e0fa044accd774cb097e7861ea0b01b58a89e4f58aa