[INFO] cloning repository https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/halfzebra/rust-smart-pointers-examples" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples'...
[INFO] [stderr] /workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples: No space left on device
[WARN] Retrying crate fetch in 3 seconds (attempt 1)
[INFO] cloning repository https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/halfzebra/rust-smart-pointers-examples" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples'...
[INFO] [stderr] /workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples: No space left on device
[WARN] Retrying crate fetch in 3 seconds (attempt 2)
[INFO] cloning repository https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/halfzebra/rust-smart-pointers-examples" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples'...
[INFO] [stderr] /workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples: No space left on device
[WARN] Retrying crate fetch in 3 seconds (attempt 3)
[INFO] cloning repository https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/halfzebra/rust-smart-pointers-examples" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples'...
[INFO] [stderr] /workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples: No space left on device
[WARN] Retrying crate fetch in 3 seconds (attempt 4)
[INFO] cloning repository https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/halfzebra/rust-smart-pointers-examples" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples'...
[INFO] [stderr] /workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples: No space left on device
[WARN] Retrying crate fetch in 3 seconds (attempt 5)
[INFO] cloning repository https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/halfzebra/rust-smart-pointers-examples" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples'...
[INFO] [stderr] /workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples: No space left on device
[WARN] Retrying crate fetch in 3 seconds (attempt 6)
[INFO] cloning repository https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/halfzebra/rust-smart-pointers-examples" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples'...
[INFO] [stderr] /workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples: No space left on device
[WARN] Retrying crate fetch in 3 seconds (attempt 7)
[INFO] cloning repository https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/halfzebra/rust-smart-pointers-examples" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] d0f57ba42e7466e89ac79f06a9ce5a0f97765967
[INFO] checking halfzebra/rust-smart-pointers-examples against master#01706e1a34c87656fcbfce198608f4cd2ac6461a for pr-135272
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fhalfzebra%2Frust-smart-pointers-examples" "/workspace/builds/worker-0-tc1/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-0-tc1/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/halfzebra/rust-smart-pointers-examples on toolchain 01706e1a34c87656fcbfce198608f4cd2ac6461a
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+01706e1a34c87656fcbfce198608f4cd2ac6461a" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking git repo https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] finished tweaking git repo https://github.com/halfzebra/rust-smart-pointers-examples
[INFO] tweaked toml for git repo https://github.com/halfzebra/rust-smart-pointers-examples written to /workspace/builds/worker-0-tc1/source/Cargo.toml
[INFO] crate git repo https://github.com/halfzebra/rust-smart-pointers-examples 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" "+01706e1a34c87656fcbfce198608f4cd2ac6461a" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc1/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@sha256:819108c5571ea2e421544af4d832f968d213c87fbe3707a016657f43d2f853bc" "/opt/rustwide/cargo-home/bin/cargo" "+01706e1a34c87656fcbfce198608f4cd2ac6461a" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 308938031ebd15b7ee649f39da1b69c4e3d7ae535e1cab8570fb5c6cbbef22e3
[INFO] running `Command { std: "docker" "start" "-a" "308938031ebd15b7ee649f39da1b69c4e3d7ae535e1cab8570fb5c6cbbef22e3", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "308938031ebd15b7ee649f39da1b69c4e3d7ae535e1cab8570fb5c6cbbef22e3", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "308938031ebd15b7ee649f39da1b69c4e3d7ae535e1cab8570fb5c6cbbef22e3", kill_on_drop: false }`
[INFO] [stdout] 308938031ebd15b7ee649f39da1b69c4e3d7ae535e1cab8570fb5c6cbbef22e3
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc1/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@sha256:819108c5571ea2e421544af4d832f968d213c87fbe3707a016657f43d2f853bc" "/opt/rustwide/cargo-home/bin/cargo" "+01706e1a34c87656fcbfce198608f4cd2ac6461a" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 3cb784aed2a3d48db491858748275fe8deb11ea73e7c3b056b5cff13db1f91c7
[INFO] running `Command { std: "docker" "start" "-a" "3cb784aed2a3d48db491858748275fe8deb11ea73e7c3b056b5cff13db1f91c7", kill_on_drop: false }`
[INFO] [stderr]     Checking rust-smart-pointers-examples v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: trait `Messenger` is never used
[INFO] [stdout]  --> src/messenger.rs:1:11
[INFO] [stdout]   |
[INFO] [stdout] 1 | pub trait Messenger {
[INFO] [stdout]   |           ^^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: struct `LimitTracker` is never constructed
[INFO] [stdout]  --> src/limit_tracker.rs:4:12
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub struct LimitTracker<'a, T: Messenger> {
[INFO] [stdout]   |            ^^^^^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: `LimitTracker` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: associated items `new` and `set_value` are never used
[INFO] [stdout]   --> src/limit_tracker.rs:14:12
[INFO] [stdout]    |
[INFO] [stdout] 10 | / impl<'a, T> LimitTracker<'a, T>
[INFO] [stdout] 11 | | where
[INFO] [stdout] 12 | |     T: Messenger,
[INFO] [stdout]    | |_________________- associated items in this implementation
[INFO] [stdout] 13 |   {
[INFO] [stdout] 14 |       pub fn new(messenger: &T, max: usize) -> LimitTracker<T> {
[INFO] [stdout]    |              ^^^
[INFO] [stdout] ...
[INFO] [stdout] 22 |       pub fn set_value(&mut self, value: usize) {
[INFO] [stdout]    |              ^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused borrow that must be used
[INFO] [stdout]   --> src/limit_tracker.rs:62:13
[INFO] [stdout]    |
[INFO] [stdout] 62 |             &self.sent_messages.borrow_mut().push(String::from(message));
[INFO] [stdout]    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the borrow produces a value
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_must_use)]` on by default
[INFO] [stdout] help: use `let _ = ...` to ignore the resulting value
[INFO] [stdout]    |
[INFO] [stdout] 62 |             let _ = &self.sent_messages.borrow_mut().push(String::from(message));
[INFO] [stdout]    |             +++++++
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field `value` is never read
[INFO] [stdout]   --> src/main.rs:33:5
[INFO] [stdout]    |
[INFO] [stdout] 32 | struct CustomPointer<T> {
[INFO] [stdout]    |        ------------- field in this struct
[INFO] [stdout] 33 |     value: T,
[INFO] [stdout]    |     ^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `CustomPointer` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout]    = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: fields `0` and `1` are never read
[INFO] [stdout]  --> src/linked_list_tail_box.rs:4:10
[INFO] [stdout]   |
[INFO] [stdout] 4 |     Cons(i32, Box<List>),
[INFO] [stdout]   |     ---- ^^^  ^^^^^^^^^
[INFO] [stdout]   |     |
[INFO] [stdout]   |     fields in this variant
[INFO] [stdout]   |
[INFO] [stdout]   = note: `List` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
[INFO] [stdout]   |
[INFO] [stdout] 4 |     Cons((), ()),
[INFO] [stdout]   |          ~~  ~~
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: fields `0` and `1` are never read
[INFO] [stdout]  --> src/linked_list_tail_rc.rs:9:10
[INFO] [stdout]   |
[INFO] [stdout] 9 |     Cons(i32, Rc<List>),
[INFO] [stdout]   |     ---- ^^^  ^^^^^^^^
[INFO] [stdout]   |     |
[INFO] [stdout]   |     fields in this variant
[INFO] [stdout]   |
[INFO] [stdout]   = note: `List` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
[INFO] [stdout]   |
[INFO] [stdout] 9 |     Cons((), ()),
[INFO] [stdout]   |          ~~  ~~
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: fields `0` and `1` are never read
[INFO] [stdout]  --> src/list_with_mutable_value.rs:7:10
[INFO] [stdout]   |
[INFO] [stdout] 7 |     Cons(Rc<RefCell<i32>>, Rc<List>),
[INFO] [stdout]   |     ---- ^^^^^^^^^^^^^^^^  ^^^^^^^^
[INFO] [stdout]   |     |
[INFO] [stdout]   |     fields in this variant
[INFO] [stdout]   |
[INFO] [stdout]   = note: `List` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
[INFO] [stdout]   |
[INFO] [stdout] 7 |     Cons((), ()),
[INFO] [stdout]   |          ~~  ~~
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field `0` is never read
[INFO] [stdout]  --> src/reference_cycle.rs:7:10
[INFO] [stdout]   |
[INFO] [stdout] 7 |     Cons(i32, RefCell<Rc<List>>),
[INFO] [stdout]   |     ---- ^^^
[INFO] [stdout]   |     |
[INFO] [stdout]   |     field in this variant
[INFO] [stdout]   |
[INFO] [stdout]   = note: `List` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
[INFO] [stdout]   |
[INFO] [stdout] 7 |     Cons((), RefCell<Rc<List>>),
[INFO] [stdout]   |          ~~
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: fields `value` and `children` are never read
[INFO] [stdout]  --> src/reference_cycle_tree.rs:6:5
[INFO] [stdout]   |
[INFO] [stdout] 5 | struct Node {
[INFO] [stdout]   |        ---- fields in this struct
[INFO] [stdout] 6 |     value: i32,
[INFO] [stdout]   |     ^^^^^
[INFO] [stdout] 7 |     children: RefCell<Vec<Rc<Node>>>,
[INFO] [stdout]   |     ^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: `Node` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field `value` is never read
[INFO] [stdout]   --> src/main.rs:33:5
[INFO] [stdout]    |
[INFO] [stdout] 32 | struct CustomPointer<T> {
[INFO] [stdout]    |        ------------- field in this struct
[INFO] [stdout] 33 |     value: T,
[INFO] [stdout]    |     ^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `CustomPointer` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout]    = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: fields `0` and `1` are never read
[INFO] [stdout]  --> src/linked_list_tail_box.rs:4:10
[INFO] [stdout]   |
[INFO] [stdout] 4 |     Cons(i32, Box<List>),
[INFO] [stdout]   |     ---- ^^^  ^^^^^^^^^
[INFO] [stdout]   |     |
[INFO] [stdout]   |     fields in this variant
[INFO] [stdout]   |
[INFO] [stdout]   = note: `List` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
[INFO] [stdout]   |
[INFO] [stdout] 4 |     Cons((), ()),
[INFO] [stdout]   |          ~~  ~~
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: fields `0` and `1` are never read
[INFO] [stdout]  --> src/linked_list_tail_rc.rs:9:10
[INFO] [stdout]   |
[INFO] [stdout] 9 |     Cons(i32, Rc<List>),
[INFO] [stdout]   |     ---- ^^^  ^^^^^^^^
[INFO] [stdout]   |     |
[INFO] [stdout]   |     fields in this variant
[INFO] [stdout]   |
[INFO] [stdout]   = note: `List` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
[INFO] [stdout]   |
[INFO] [stdout] 9 |     Cons((), ()),
[INFO] [stdout]   |          ~~  ~~
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: fields `0` and `1` are never read
[INFO] [stdout]  --> src/list_with_mutable_value.rs:7:10
[INFO] [stdout]   |
[INFO] [stdout] 7 |     Cons(Rc<RefCell<i32>>, Rc<List>),
[INFO] [stdout]   |     ---- ^^^^^^^^^^^^^^^^  ^^^^^^^^
[INFO] [stdout]   |     |
[INFO] [stdout]   |     fields in this variant
[INFO] [stdout]   |
[INFO] [stdout]   = note: `List` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
[INFO] [stdout]   |
[INFO] [stdout] 7 |     Cons((), ()),
[INFO] [stdout]   |          ~~  ~~
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field `0` is never read
[INFO] [stdout]  --> src/reference_cycle.rs:7:10
[INFO] [stdout]   |
[INFO] [stdout] 7 |     Cons(i32, RefCell<Rc<List>>),
[INFO] [stdout]   |     ---- ^^^
[INFO] [stdout]   |     |
[INFO] [stdout]   |     field in this variant
[INFO] [stdout]   |
[INFO] [stdout]   = note: `List` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
[INFO] [stdout]   |
[INFO] [stdout] 7 |     Cons((), RefCell<Rc<List>>),
[INFO] [stdout]   |          ~~
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: fields `value` and `children` are never read
[INFO] [stdout]  --> src/reference_cycle_tree.rs:6:5
[INFO] [stdout]   |
[INFO] [stdout] 5 | struct Node {
[INFO] [stdout]   |        ---- fields in this struct
[INFO] [stdout] 6 |     value: i32,
[INFO] [stdout]   |     ^^^^^
[INFO] [stdout] 7 |     children: RefCell<Vec<Rc<Node>>>,
[INFO] [stdout]   |     ^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: `Node` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.14s
[INFO] running `Command { std: "docker" "inspect" "3cb784aed2a3d48db491858748275fe8deb11ea73e7c3b056b5cff13db1f91c7", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "3cb784aed2a3d48db491858748275fe8deb11ea73e7c3b056b5cff13db1f91c7", kill_on_drop: false }`
[INFO] [stdout] 3cb784aed2a3d48db491858748275fe8deb11ea73e7c3b056b5cff13db1f91c7
