[INFO] cloning repository https://github.com/arashout/rust_linkedlist
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/arashout/rust_linkedlist" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Farashout%2Frust_linkedlist", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Farashout%2Frust_linkedlist'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 1e6015ad0ec7684f3091ed0f40001734934354c9
[INFO] checking arashout/rust_linkedlist against try#ad93f57d532978d6739002a21bc66b45ed22f998 for pr-155418
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Farashout%2Frust_linkedlist" "/workspace/builds/worker-6-tc2/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-6-tc2/source'...
[INFO] [stderr] done.
[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-6-tc2/source/Cargo.toml
[INFO] validating manifest of git repo https://github.com/arashout/rust_linkedlist on toolchain ad93f57d532978d6739002a21bc66b45ed22f998
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+ad93f57d532978d6739002a21bc66b45ed22f998" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] crate git repo https://github.com/arashout/rust_linkedlist 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" "+ad93f57d532978d6739002a21bc66b45ed22f998" "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
[ERROR] error running command: no output for 300 seconds
[INFO] checking arashout/rust_linkedlist against try#ad93f57d532978d6739002a21bc66b45ed22f998 for pr-155418
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Farashout%2Frust_linkedlist" "/workspace/builds/worker-6-tc2/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-6-tc2/source'...
[INFO] [stderr] done.
[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-6-tc2/source/Cargo.toml
[INFO] validating manifest of git repo https://github.com/arashout/rust_linkedlist on toolchain ad93f57d532978d6739002a21bc66b45ed22f998
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+ad93f57d532978d6739002a21bc66b45ed22f998" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] crate git repo https://github.com/arashout/rust_linkedlist 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" "+ad93f57d532978d6739002a21bc66b45ed22f998" "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-6-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-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:d429b63d4308055ea97f60fb1d3dfca48854a00942f1bd2ad806beaf015945ec" "/opt/rustwide/cargo-home/bin/cargo" "+ad93f57d532978d6739002a21bc66b45ed22f998" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] ef02f18750c204d20d70fa0a003b516169d183c130a00e05586cf8ba747423da
[INFO] running `Command { std: "docker" "start" "-a" "ef02f18750c204d20d70fa0a003b516169d183c130a00e05586cf8ba747423da", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "ef02f18750c204d20d70fa0a003b516169d183c130a00e05586cf8ba747423da", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "ef02f18750c204d20d70fa0a003b516169d183c130a00e05586cf8ba747423da", kill_on_drop: false }`
[INFO] [stdout] ef02f18750c204d20d70fa0a003b516169d183c130a00e05586cf8ba747423da
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-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:d429b63d4308055ea97f60fb1d3dfca48854a00942f1bd2ad806beaf015945ec" "/opt/rustwide/cargo-home/bin/cargo" "+ad93f57d532978d6739002a21bc66b45ed22f998" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 8763ff12225b9f912e5c9f330a9ac8c7a7727ac3abbfafcd86f0e0b49152fa20
[INFO] running `Command { std: "docker" "start" "-a" "8763ff12225b9f912e5c9f330a9ac8c7a7727ac3abbfafcd86f0e0b49152fa20", kill_on_drop: false }`
[INFO] [stderr]     Checking linkedlist v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: unused variable: `old_tail`
[INFO] [stdout]   --> src/fourth.rs:67:18
[INFO] [stdout]    |
[INFO] [stdout] 67 |             Some(old_tail) => {
[INFO] [stdout]    |                  ^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_old_tail`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `List` is never constructed
[INFO] [stdout]  --> src/first.rs:4:12
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub struct List {
[INFO] [stdout]   |            ^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: enum `Link` is never used
[INFO] [stdout]  --> src/first.rs:9:6
[INFO] [stdout]   |
[INFO] [stdout] 9 | enum Link {
[INFO] [stdout]   |      ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `Node` is never constructed
[INFO] [stdout]   --> src/first.rs:15:8
[INFO] [stdout]    |
[INFO] [stdout] 15 | struct Node {
[INFO] [stdout]    |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: associated items `new`, `push`, and `pop` are never used
[INFO] [stdout]   --> src/first.rs:21:12
[INFO] [stdout]    |
[INFO] [stdout] 20 | impl List {
[INFO] [stdout]    | --------- associated items in this implementation
[INFO] [stdout] 21 |     pub fn new()-> Self {
[INFO] [stdout]    |            ^^^
[INFO] [stdout] ...
[INFO] [stdout] 25 |     pub fn push(&mut self, elem: i32) {
[INFO] [stdout]    |            ^^^^
[INFO] [stdout] ...
[INFO] [stdout] 33 |     pub fn pop(&mut self) -> Option<i32> {
[INFO] [stdout]    |            ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `List` is never constructed
[INFO] [stdout]  --> src/second.rs:1:12
[INFO] [stdout]   |
[INFO] [stdout] 1 | pub struct List<T> {
[INFO] [stdout]   |            ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: type alias `Link` is never used
[INFO] [stdout]  --> src/second.rs:5:6
[INFO] [stdout]   |
[INFO] [stdout] 5 | type Link<T> = Option<Box<Node<T>>>;
[INFO] [stdout]   |      ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `Node` is never constructed
[INFO] [stdout]  --> src/second.rs:7:8
[INFO] [stdout]   |
[INFO] [stdout] 7 | struct Node<T> {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: associated items `new`, `push`, `pop`, `peek`, and `peek_mut` are never used
[INFO] [stdout]   --> src/second.rs:13:12
[INFO] [stdout]    |
[INFO] [stdout] 12 | impl<T> List<T> {
[INFO] [stdout]    | --------------- associated items in this implementation
[INFO] [stdout] 13 |     pub fn new() -> Self {
[INFO] [stdout]    |            ^^^
[INFO] [stdout] ...
[INFO] [stdout] 17 |     pub fn push(&mut self, elem: T) {
[INFO] [stdout]    |            ^^^^
[INFO] [stdout] ...
[INFO] [stdout] 26 |     pub fn pop(&mut self) -> Option<T> {
[INFO] [stdout]    |            ^^^
[INFO] [stdout] ...
[INFO] [stdout] 33 |     pub fn peek(&self) -> Option<&T> {
[INFO] [stdout]    |            ^^^^
[INFO] [stdout] ...
[INFO] [stdout] 37 |     pub fn peek_mut(&mut self) -> Option<&mut T> {
[INFO] [stdout]    |            ^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `IntoIter` is never constructed
[INFO] [stdout]   --> src/second.rs:47:12
[INFO] [stdout]    |
[INFO] [stdout] 47 | pub struct IntoIter<T> {
[INFO] [stdout]    |            ^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: method `into_iter` is never used
[INFO] [stdout]   --> src/second.rs:52:12
[INFO] [stdout]    |
[INFO] [stdout] 51 | impl<T> List<T> {
[INFO] [stdout]    | --------------- method in this implementation
[INFO] [stdout] 52 |     pub fn into_iter(self) -> IntoIter<T> {
[INFO] [stdout]    |            ^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `Iter` is never constructed
[INFO] [stdout]   --> src/second.rs:65:12
[INFO] [stdout]    |
[INFO] [stdout] 65 | pub struct Iter<'a, T> {
[INFO] [stdout]    |            ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: method `iter` is never used
[INFO] [stdout]   --> src/second.rs:70:12
[INFO] [stdout]    |
[INFO] [stdout] 69 | impl<T> List<T> {
[INFO] [stdout]    | --------------- method in this implementation
[INFO] [stdout] 70 |     pub fn iter<'a>(&'a self) -> Iter<'a, T> {
[INFO] [stdout]    |            ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `IterMut` is never constructed
[INFO] [stdout]   --> src/second.rs:87:12
[INFO] [stdout]    |
[INFO] [stdout] 87 | pub struct IterMut<'a, T> {
[INFO] [stdout]    |            ^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: method `iter_mut` is never used
[INFO] [stdout]   --> src/second.rs:92:12
[INFO] [stdout]    |
[INFO] [stdout] 91 | impl<T> List<T> {
[INFO] [stdout]    | --------------- method in this implementation
[INFO] [stdout] 92 |     pub fn iter_mut(&mut self) -> IterMut<'_, T> {
[INFO] [stdout]    |            ^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `List` is never constructed
[INFO] [stdout]  --> src/third.rs:3:12
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub struct List<T> {
[INFO] [stdout]   |            ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: type alias `Link` is never used
[INFO] [stdout]  --> src/third.rs:7:6
[INFO] [stdout]   |
[INFO] [stdout] 7 | type Link<T> = Option<Rc<Node<T>>>;
[INFO] [stdout]   |      ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `Node` is never constructed
[INFO] [stdout]  --> src/third.rs:9:8
[INFO] [stdout]   |
[INFO] [stdout] 9 | struct Node<T> {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: associated items `new`, `append`, `tail`, and `head` are never used
[INFO] [stdout]   --> src/third.rs:15:12
[INFO] [stdout]    |
[INFO] [stdout] 14 | impl<T> List<T> {
[INFO] [stdout]    | --------------- associated items in this implementation
[INFO] [stdout] 15 |     pub fn new() -> Self {
[INFO] [stdout]    |            ^^^
[INFO] [stdout] ...
[INFO] [stdout] 18 |     pub fn append(&self, elem: T) -> List<T> {
[INFO] [stdout]    |            ^^^^^^
[INFO] [stdout] ...
[INFO] [stdout] 26 |     pub fn tail(&self) -> List<T> {
[INFO] [stdout]    |            ^^^^
[INFO] [stdout] ...
[INFO] [stdout] 31 |     pub fn head(&self) -> Option<&T> {
[INFO] [stdout]    |            ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `Iter` is never constructed
[INFO] [stdout]   --> src/third.rs:36:12
[INFO] [stdout]    |
[INFO] [stdout] 36 | pub struct Iter<'a, T> {
[INFO] [stdout]    |            ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: method `iter` is never used
[INFO] [stdout]   --> src/third.rs:41:12
[INFO] [stdout]    |
[INFO] [stdout] 40 | impl<T> List<T> {
[INFO] [stdout]    | --------------- method in this implementation
[INFO] [stdout] 41 |     pub fn iter(&self) -> Iter<'_, T> {
[INFO] [stdout]    |            ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `List` is never constructed
[INFO] [stdout]  --> src/fourth.rs:4:12
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub struct List<T> {
[INFO] [stdout]   |            ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: type alias `Link` is never used
[INFO] [stdout]  --> src/fourth.rs:9:6
[INFO] [stdout]   |
[INFO] [stdout] 9 | type Link<T> = Option<Rc<RefCell<Node<T>>>>;
[INFO] [stdout]   |      ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `Node` is never constructed
[INFO] [stdout]   --> src/fourth.rs:11:8
[INFO] [stdout]    |
[INFO] [stdout] 11 | struct Node<T> {
[INFO] [stdout]    |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: associated function `new` is never used
[INFO] [stdout]   --> src/fourth.rs:18:8
[INFO] [stdout]    |
[INFO] [stdout] 17 | impl<T> Node<T> {
[INFO] [stdout]    | --------------- associated function in this implementation
[INFO] [stdout] 18 |     fn new(elem: T) -> Rc<RefCell<Self>> {
[INFO] [stdout]    |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: associated items `new`, `push_front`, `pop_front`, `push_back`, and `peek_front` are never used
[INFO] [stdout]   --> src/fourth.rs:28:12
[INFO] [stdout]    |
[INFO] [stdout] 27 | impl<T> List<T> {
[INFO] [stdout]    | --------------- associated items in this implementation
[INFO] [stdout] 28 |     pub fn new() -> Self {
[INFO] [stdout]    |            ^^^
[INFO] [stdout] ...
[INFO] [stdout] 34 |     pub fn push_front(&mut self, elem: T) {
[INFO] [stdout]    |            ^^^^^^^^^^
[INFO] [stdout] ...
[INFO] [stdout] 48 |     pub fn pop_front(&mut self) -> Option<T> {
[INFO] [stdout]    |            ^^^^^^^^^
[INFO] [stdout] ...
[INFO] [stdout] 64 |     pub fn push_back(&mut self, elem: T) {
[INFO] [stdout]    |            ^^^^^^^^^
[INFO] [stdout] ...
[INFO] [stdout] 76 |     pub fn peek_front(&self) -> Option<Ref<T>> {
[INFO] [stdout]    |            ^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: hiding a lifetime that's elided elsewhere is confusing
[INFO] [stdout]   --> src/fourth.rs:76:23
[INFO] [stdout]    |
[INFO] [stdout] 76 |     pub fn peek_front(&self) -> Option<Ref<T>> {
[INFO] [stdout]    |                       ^^^^^            ^^^^^^ the same lifetime is hidden here
[INFO] [stdout]    |                       |
[INFO] [stdout]    |                       the lifetime is elided here
[INFO] [stdout]    |
[INFO] [stdout]    = help: the same lifetime is referred to in inconsistent ways, making the signature confusing
[INFO] [stdout]    = note: `#[warn(mismatched_lifetime_syntaxes)]` on by default
[INFO] [stdout] help: use `'_` for type paths
[INFO] [stdout]    |
[INFO] [stdout] 76 |     pub fn peek_front(&self) -> Option<Ref<'_, T>> {
[INFO] [stdout]    |                                            +++
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `old_tail`
[INFO] [stdout]   --> src/fourth.rs:67:18
[INFO] [stdout]    |
[INFO] [stdout] 67 |             Some(old_tail) => {
[INFO] [stdout]    |                  ^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_old_tail`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: method `push_back` is never used
[INFO] [stdout]   --> src/fourth.rs:64:12
[INFO] [stdout]    |
[INFO] [stdout] 27 | impl<T> List<T> {
[INFO] [stdout]    | --------------- method in this implementation
[INFO] [stdout] ...
[INFO] [stdout] 64 |     pub fn push_back(&mut self, elem: T) {
[INFO] [stdout]    |            ^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: hiding a lifetime that's elided elsewhere is confusing
[INFO] [stdout]   --> src/fourth.rs:76:23
[INFO] [stdout]    |
[INFO] [stdout] 76 |     pub fn peek_front(&self) -> Option<Ref<T>> {
[INFO] [stdout]    |                       ^^^^^            ^^^^^^ the same lifetime is hidden here
[INFO] [stdout]    |                       |
[INFO] [stdout]    |                       the lifetime is elided here
[INFO] [stdout]    |
[INFO] [stdout]    = help: the same lifetime is referred to in inconsistent ways, making the signature confusing
[INFO] [stdout]    = note: `#[warn(mismatched_lifetime_syntaxes)]` on by default
[INFO] [stdout] help: use `'_` for type paths
[INFO] [stdout]    |
[INFO] [stdout] 76 |     pub fn peek_front(&self) -> Option<Ref<'_, T>> {
[INFO] [stdout]    |                                            +++
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.13s
[INFO] running `Command { std: "docker" "inspect" "8763ff12225b9f912e5c9f330a9ac8c7a7727ac3abbfafcd86f0e0b49152fa20", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "8763ff12225b9f912e5c9f330a9ac8c7a7727ac3abbfafcd86f0e0b49152fa20", kill_on_drop: false }`
[INFO] [stdout] 8763ff12225b9f912e5c9f330a9ac8c7a7727ac3abbfafcd86f0e0b49152fa20