[INFO] fetching crate colon 0.1.0...
[INFO] checking colon-0.1.0 against try#f47dd4da3ae8c32c9e65d307bfe640b143e674df for pr-77526
[INFO] extracting crate colon 0.1.0 into /workspace/builds/worker-0/source
[INFO] validating manifest of crates.io crate colon 0.1.0 on toolchain f47dd4da3ae8c32c9e65d307bfe640b143e674df
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+f47dd4da3ae8c32c9e65d307bfe640b143e674df" "read-manifest" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] started tweaking crates.io crate colon 0.1.0
[INFO] finished tweaking crates.io crate colon 0.1.0
[INFO] tweaked toml for crates.io crate colon 0.1.0 written to /workspace/builds/worker-0/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+f47dd4da3ae8c32c9e65d307bfe640b143e674df" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+f47dd4da3ae8c32c9e65d307bfe640b143e674df" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/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:d92eaeed33fa75130ca1ee6c8a01d1ffb62bac859dfdfb3450e3e5d1c0146529" "/opt/rustwide/cargo-home/bin/cargo" "+f47dd4da3ae8c32c9e65d307bfe640b143e674df" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 214270265aa882592ad12e8cfec5d47fcbca0287805f1ec2bd647b5c627653a8
[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" "214270265aa882592ad12e8cfec5d47fcbca0287805f1ec2bd647b5c627653a8", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "214270265aa882592ad12e8cfec5d47fcbca0287805f1ec2bd647b5c627653a8", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "214270265aa882592ad12e8cfec5d47fcbca0287805f1ec2bd647b5c627653a8", kill_on_drop: false }`
[INFO] [stdout] 214270265aa882592ad12e8cfec5d47fcbca0287805f1ec2bd647b5c627653a8
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/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:d92eaeed33fa75130ca1ee6c8a01d1ffb62bac859dfdfb3450e3e5d1c0146529" "/opt/rustwide/cargo-home/bin/cargo" "+f47dd4da3ae8c32c9e65d307bfe640b143e674df" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] c55d8a893d6dc99332e50f893dcc0c133d9b130b326ba73df8063cb6f91ebd84
[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" "c55d8a893d6dc99332e50f893dcc0c133d9b130b326ba73df8063cb6f91ebd84", kill_on_drop: false }`
[INFO] [stderr]    Compiling autocfg v1.0.1
[INFO] [stderr]    Compiling num-traits v0.2.12
[INFO] [stderr]     Checking colon v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: unused variable: `i`
[INFO] [stdout]   --> src/sorted_index.rs:10:8
[INFO] [stdout]    |
[INFO] [stdout] 10 |     Ok(i) => {
[INFO] [stdout]    |        ^ help: if this is intentional, prefix it with an underscore: `_i`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `chunk`
[INFO] [stdout]  --> src/chunk.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn chunk<T: Clone>(v: Vec<T>, n: usize) -> Vec<Vec<T>> {
[INFO] [stdout]   |        ^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `compact`
[INFO] [stdout]  --> src/compact.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn compact<T: Clone>(v: Vec<Option<T>>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `concat`
[INFO] [stdout]  --> src/concat.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn concat<T: Clone>(v1: Vec<T>, v2: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `difference`
[INFO] [stdout]  --> src/difference.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn difference<T: Clone + Eq>(v1: Vec<T>, v2: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `drop`
[INFO] [stdout]  --> src/drop.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn drop<T: Clone>(v: Vec<T>, n: usize) -> Vec<T> {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `fill`
[INFO] [stdout]  --> src/fill.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn fill<T: Clone>(v: Vec<T>, val: T) -> Vec<T> {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `find_index`
[INFO] [stdout]  --> src/find_index.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn find_index<T: Clone, F>(v: Vec<T>, f: F) -> usize
[INFO] [stdout]   |        ^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `find_last_index`
[INFO] [stdout]  --> src/find_last_index.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn find_last_index<T: Clone, F>(v: Vec<T>, f: F) -> usize
[INFO] [stdout]   |        ^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `first`
[INFO] [stdout]  --> src/first.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn first<T: Clone>(v: Vec<T>) -> Option<T> {
[INFO] [stdout]   |        ^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `flatten`
[INFO] [stdout]  --> src/flatten.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn flatten<T>(v: Vec<Vec<T>>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `from_pairs`
[INFO] [stdout]  --> src/from_pairs.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn from_pairs<T: Clone>(v: Vec<(&str, T)>) -> HashMap<&str, T> {
[INFO] [stdout]   |        ^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `head`
[INFO] [stdout]  --> src/head.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn head<T: Clone>(v: Vec<T>) -> Option<T> {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `index_of`
[INFO] [stdout]  --> src/index_of.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn index_of<T: Clone + PartialEq>(v: Vec<T>, val: T) -> usize {
[INFO] [stdout]   |        ^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `initial`
[INFO] [stdout]  --> src/initial.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn initial<T: Clone>(mut v: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `intersection`
[INFO] [stdout]  --> src/intersection.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn intersection<T: Clone + Eq>(v1: Vec<T>, v2: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `join`
[INFO] [stdout]  --> src/join.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn join<T: Clone + ToString>(v: Vec<T>, sep: &str) -> String {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `last`
[INFO] [stdout]  --> src/last.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn last<T: Clone>(v: Vec<T>) -> Option<T> {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `last_index_of`
[INFO] [stdout]  --> src/last_index_of.rs:6:8
[INFO] [stdout]   |
[INFO] [stdout] 6 | pub fn last_index_of<T: Clone + PartialEq + Ord>(v: Vec<T>, val: T) -> usize {
[INFO] [stdout]   |        ^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `nth`
[INFO] [stdout]  --> src/nth.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn nth<T: Clone>(v: Vec<T>, idx: isize) -> Option<T> {
[INFO] [stdout]   |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `pull`
[INFO] [stdout]  --> src/pull.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn pull<T: PartialEq>(v: &mut Vec<T>, vals: Vec<T>) {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `pull_at`
[INFO] [stdout]  --> src/pull_at.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn pull_at<T: PartialEq>(v: &mut Vec<T>, mut idxs: Vec<usize>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `remove`
[INFO] [stdout]  --> src/remove.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn remove<T: Clone, F>(v: &mut Vec<T>, f: F) -> Vec<T>
[INFO] [stdout]   |        ^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `reverse`
[INFO] [stdout]  --> src/reverse.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn reverse<T: Clone>(v: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `slice`
[INFO] [stdout]  --> src/slice.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn slice<T: Clone>(v: Vec<T>, start: usize, end: usize) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `sorted_index`
[INFO] [stdout]  --> src/sorted_index.rs:6:8
[INFO] [stdout]   |
[INFO] [stdout] 6 | pub fn sorted_index<T: Clone + PartialEq + PartialOrd>(v: Vec<T>, val: T) -> usize {
[INFO] [stdout]   |        ^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `sorted_last_index`
[INFO] [stdout]  --> src/sorted_last_index.rs:6:8
[INFO] [stdout]   |
[INFO] [stdout] 6 | pub fn sorted_last_index<T: Clone + PartialEq + PartialOrd>(v: Vec<T>, val: T) -> usize {
[INFO] [stdout]   |        ^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `sorted_uniq`
[INFO] [stdout]  --> src/sorted_uniq.rs:6:8
[INFO] [stdout]   |
[INFO] [stdout] 6 | pub fn sorted_uniq<T: Clone + PartialEq + PartialOrd>(v: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `tail`
[INFO] [stdout]  --> src/tail.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn tail<T: Clone>(v: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `take`
[INFO] [stdout]  --> src/take.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn take<T: Clone>(v: Vec<T>, n: usize) -> Vec<T> {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `take_right`
[INFO] [stdout]  --> src/take_right.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn take_right<T: Clone>(v: Vec<T>, n: usize) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `union`
[INFO] [stdout]  --> src/union.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn union<T: Clone + PartialEq>(v1: Vec<T>, v2: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `unzip`
[INFO] [stdout]  --> src/unzip.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn unzip<T: Clone>(v: Vec<Vec<T>>) -> Vec<Vec<T>> {
[INFO] [stdout]   |        ^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `without`
[INFO] [stdout]  --> src/without.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn without<T: Clone + PartialEq>(v: Vec<T>, vals: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `xor`
[INFO] [stdout]  --> src/xor.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn xor<T: Clone + Eq>(v1: Vec<T>, v2: Vec<T>) -> Vec<T> {
[INFO] [stdout]   |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `zip`
[INFO] [stdout]  --> src/zip.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn zip<T: Clone>(v: Vec<Vec<T>>) -> Vec<Vec<T>> {
[INFO] [stdout]   |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `add`
[INFO] [stdout]  --> src/add.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn add<T: Signed + FromPrimitive>(v1: T, v2: T) -> T {
[INFO] [stdout]   |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `ceil`
[INFO] [stdout]  --> src/ceil.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn ceil<T: Float + Signed + FromPrimitive>(v: T, precision: i32) -> T {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `divide`
[INFO] [stdout]  --> src/divide.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn divide<T: Float + Signed + FromPrimitive>(dividend: T, divisor: T) -> T {
[INFO] [stdout]   |        ^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `floor`
[INFO] [stdout]  --> src/floor.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn floor<T: Float + Signed + FromPrimitive>(v: T, precision: i32) -> T {
[INFO] [stdout]   |        ^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `max`
[INFO] [stdout]  --> src/max.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn max<T: Copy + Ord>(v: Vec<T>) -> T {
[INFO] [stdout]   |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `mean`
[INFO] [stdout]  --> src/mean.rs:9:8
[INFO] [stdout]   |
[INFO] [stdout] 9 | pub fn mean<T: Copy + Sum + Div + PartialEq + FromPrimitive + ToPrimitive>(v: Vec<T>) -> f64 {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `min`
[INFO] [stdout]  --> src/min.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn min<T: Copy + Ord>(v: Vec<T>) -> T {
[INFO] [stdout]   |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `multiply`
[INFO] [stdout]  --> src/multiply.rs:7:8
[INFO] [stdout]   |
[INFO] [stdout] 7 | pub fn multiply<A, B>(v1: A, v2: B) -> f64
[INFO] [stdout]   |        ^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `round`
[INFO] [stdout]  --> src/round.rs:4:8
[INFO] [stdout]   |
[INFO] [stdout] 4 | pub fn round<T: Float + Signed + FromPrimitive>(v: T, precision: i32) -> T {
[INFO] [stdout]   |        ^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `subtract`
[INFO] [stdout]  --> src/subtract.rs:7:8
[INFO] [stdout]   |
[INFO] [stdout] 7 | pub fn subtract<A, B>(v1: A, v2: B) -> f64
[INFO] [stdout]   |        ^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `sum`
[INFO] [stdout]  --> src/sum.rs:7:8
[INFO] [stdout]   |
[INFO] [stdout] 7 | pub fn sum<T: Copy + Sum + ToPrimitive>(v: Vec<T>) -> f64 {
[INFO] [stdout]   |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 47 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `i`
[INFO] [stdout]   --> src/sorted_index.rs:10:8
[INFO] [stdout]    |
[INFO] [stdout] 10 |     Ok(i) => {
[INFO] [stdout]    |        ^ help: if this is intentional, prefix it with an underscore: `_i`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `head`
[INFO] [stdout]  --> src/head.rs:3:8
[INFO] [stdout]   |
[INFO] [stdout] 3 | pub fn head<T: Clone>(v: Vec<T>) -> Option<T> {
[INFO] [stdout]   |        ^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `index_of`
[INFO] [stdout]  --> src/index_of.rs:5:8
[INFO] [stdout]   |
[INFO] [stdout] 5 | pub fn index_of<T: Clone + PartialEq>(v: Vec<T>, val: T) -> usize {
[INFO] [stdout]   |        ^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `last_index_of`
[INFO] [stdout]  --> src/last_index_of.rs:6:8
[INFO] [stdout]   |
[INFO] [stdout] 6 | pub fn last_index_of<T: Clone + PartialEq + Ord>(v: Vec<T>, val: T) -> usize {
[INFO] [stdout]   |        ^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 4 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 4.29s
[INFO] running `Command { std: "docker" "inspect" "c55d8a893d6dc99332e50f893dcc0c133d9b130b326ba73df8063cb6f91ebd84", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "c55d8a893d6dc99332e50f893dcc0c133d9b130b326ba73df8063cb6f91ebd84", kill_on_drop: false }`
[INFO] [stdout] c55d8a893d6dc99332e50f893dcc0c133d9b130b326ba73df8063cb6f91ebd84