[INFO] cloning repository https://github.com/gdemarcsek/learn-rust
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/gdemarcsek/learn-rust" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fgdemarcsek%2Flearn-rust", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fgdemarcsek%2Flearn-rust'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] c8caf07a1205b8638e5b0711fd943f663662d11d
[INFO] testing gdemarcsek/learn-rust against master#a77da2d454e6caa227a85b16410b95f93495e7e0 for pr-91031
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fgdemarcsek%2Flearn-rust" "/workspace/builds/worker-20/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-20/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/gdemarcsek/learn-rust on toolchain a77da2d454e6caa227a85b16410b95f93495e7e0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+a77da2d454e6caa227a85b16410b95f93495e7e0" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking git repo https://github.com/gdemarcsek/learn-rust
[INFO] finished tweaking git repo https://github.com/gdemarcsek/learn-rust
[INFO] tweaked toml for git repo https://github.com/gdemarcsek/learn-rust written to /workspace/builds/worker-20/source/Cargo.toml
[INFO] crate git repo https://github.com/gdemarcsek/learn-rust already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+a77da2d454e6caa227a85b16410b95f93495e7e0" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-20/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-20/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@sha256:5736fa189c1c60b01babf4b8b698fe57b6ecc41933a7ff2e0b8d7a221459412b" "/opt/rustwide/cargo-home/bin/cargo" "+a77da2d454e6caa227a85b16410b95f93495e7e0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 7edb30c3f9c0b1d8cc192a8d9b725a19c5f02f3f312df7001fa4062e152889fa
[INFO] running `Command { std: "docker" "start" "-a" "7edb30c3f9c0b1d8cc192a8d9b725a19c5f02f3f312df7001fa4062e152889fa", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "7edb30c3f9c0b1d8cc192a8d9b725a19c5f02f3f312df7001fa4062e152889fa", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "7edb30c3f9c0b1d8cc192a8d9b725a19c5f02f3f312df7001fa4062e152889fa", kill_on_drop: false }`
[INFO] [stdout] 7edb30c3f9c0b1d8cc192a8d9b725a19c5f02f3f312df7001fa4062e152889fa
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-20/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-20/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" "ghcr.io/rust-lang/crates-build-env/linux@sha256:5736fa189c1c60b01babf4b8b698fe57b6ecc41933a7ff2e0b8d7a221459412b" "/opt/rustwide/cargo-home/bin/cargo" "+a77da2d454e6caa227a85b16410b95f93495e7e0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 9e0cb1d9cc5af953be6a23a35f505dd8159c00ed1686746e1be1ea65a12af28a
[INFO] running `Command { std: "docker" "start" "-a" "9e0cb1d9cc5af953be6a23a35f505dd8159c00ed1686746e1be1ea65a12af28a", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling learn-rust v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: unnecessary trailing semicolon
[INFO] [stdout]    --> src/main.rs:200:6
[INFO] [stdout]     |
[INFO] [stdout] 200 |     };
[INFO] [stdout]     |      ^ help: remove this semicolon
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(redundant_semicolons)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused import: `std::*`
[INFO] [stdout]    --> src/main.rs:297:9
[INFO] [stdout]     |
[INFO] [stdout] 297 |     use std::*;         // glob import from Rust's standard library
[INFO] [stdout]     |         ^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(unused_imports)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unreachable pattern
[INFO] [stdout]    --> src/main.rs:269:9
[INFO] [stdout]     |
[INFO] [stdout] 269 | ...   _ => -1,    // _ is a placeholder that matches any value - if we put it as last, this will mean what the "default" label menas for ...
[INFO] [stdout]     |       ^
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(unreachable_patterns)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `x`
[INFO] [stdout]   --> src/main.rs:17:9
[INFO] [stdout]    |
[INFO] [stdout] 17 |     let x = 42;             // (type is inferred by the compiler whenever possible)
[INFO] [stdout]    |         ^ help: if this is intentional, prefix it with an underscore: `_x`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable `x` is assigned to, but never used
[INFO] [stdout]   --> src/main.rs:19:13
[INFO] [stdout]    |
[INFO] [stdout] 19 |     let mut x = 42;         // Now 'x' is declared to be mutable, thus...
[INFO] [stdout]    |             ^
[INFO] [stdout]    |
[INFO] [stdout]    = note: consider using `_x` instead
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: value assigned to `x` is never read
[INFO] [stdout]   --> src/main.rs:20:5
[INFO] [stdout]    |
[INFO] [stdout] 20 |     x = 21;                 // its value can be changed later on
[INFO] [stdout]    |     ^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_assignments)]` on by default
[INFO] [stdout]    = help: maybe it is overwritten before being read?
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `s`
[INFO] [stdout]   --> src/main.rs:40:13
[INFO] [stdout]    |
[INFO] [stdout] 40 |         let s = String::from("dynamically allocated string");           // s owns the allocated memory...
[INFO] [stdout]    |             ^ help: if this is intentional, prefix it with an underscore: `_s`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `y`
[INFO] [stdout]   --> src/main.rs:50:9
[INFO] [stdout]    |
[INFO] [stdout] 50 |     let y = x;          // a copy of the value of 'x'
[INFO] [stdout]    |         ^ help: if this is intentional, prefix it with an underscore: `_y`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `s4`
[INFO] [stdout]   --> src/main.rs:72:9
[INFO] [stdout]    |
[INFO] [stdout] 72 |     let s4 = gives_ownership();
[INFO] [stdout]    |         ^^ help: if this is intentional, prefix it with an underscore: `_s4`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `r1`
[INFO] [stdout]    --> src/main.rs:105:13
[INFO] [stdout]     |
[INFO] [stdout] 105 |         let r1 = &mut s1;
[INFO] [stdout]     |             ^^ help: if this is intentional, prefix it with an underscore: `_r1`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `r2`
[INFO] [stdout]    --> src/main.rs:110:9
[INFO] [stdout]     |
[INFO] [stdout] 110 |     let r2 = &s1;                   // but out of the scope of 'r1', we can create a reference again...
[INFO] [stdout]     |         ^^ help: if this is intentional, prefix it with an underscore: `_r2`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `r3`
[INFO] [stdout]    --> src/main.rs:111:9
[INFO] [stdout]     |
[INFO] [stdout] 111 |     let r3 = &s1;                   // ...even multiple immutable ones
[INFO] [stdout]     |         ^^ help: if this is intentional, prefix it with an underscore: `_r3`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: value assigned to `slice3` is never read
[INFO] [stdout]    --> src/main.rs:150:13
[INFO] [stdout]     |
[INFO] [stdout] 150 |     let mut slice3 = &s[1..6];
[INFO] [stdout]     |             ^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = help: maybe it is overwritten before being read?
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `slice4`
[INFO] [stdout]    --> src/main.rs:155:9
[INFO] [stdout]     |
[INFO] [stdout] 155 |     let slice4: &[i32];         // the type of each item must be 'i32'
[INFO] [stdout]     |         ^^^^^^ help: if this is intentional, prefix it with an underscore: `_slice4`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `red`
[INFO] [stdout]    --> src/main.rs:191:9
[INFO] [stdout]     |
[INFO] [stdout] 191 |     let red = RGBColor(0xff, 0x00, 0x00);
[INFO] [stdout]     |         ^^^ help: if this is intentional, prefix it with an underscore: `_red`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `foreign`
[INFO] [stdout]    --> src/main.rs:233:9
[INFO] [stdout]     |
[INFO] [stdout] 233 |     let foreign = IpAddress::V6(314159263, 123442);
[INFO] [stdout]     |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_foreign`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `some_ip`
[INFO] [stdout]    --> src/main.rs:238:9
[INFO] [stdout]     |
[INFO] [stdout] 238 |     let some_ip = Some(home);
[INFO] [stdout]     |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_some_ip`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `absent_ip`
[INFO] [stdout]    --> src/main.rs:240:9
[INFO] [stdout]     |
[INFO] [stdout] 240 |     let absent_ip: Option<IpAddress> = None; 
[INFO] [stdout]     |         ^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_absent_ip`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `x`
[INFO] [stdout]    --> src/main.rs:243:9
[INFO] [stdout]     |
[INFO] [stdout] 243 |     let x: i8 = 5;
[INFO] [stdout]     |         ^ help: if this is intentional, prefix it with an underscore: `_x`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `y`
[INFO] [stdout]    --> src/main.rs:244:9
[INFO] [stdout]     |
[INFO] [stdout] 244 |     let y: Option<i8> = Some(5);
[INFO] [stdout]     |         ^ help: if this is intentional, prefix it with an underscore: `_y`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `retcode`
[INFO] [stdout]    --> src/main.rs:259:9
[INFO] [stdout]     |
[INFO] [stdout] 259 |     let retcode = match error {     // match forces us to cover all possible cases
[INFO] [stdout]     |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_retcode`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable does not need to be mutable
[INFO] [stdout]    --> src/main.rs:139:9
[INFO] [stdout]     |
[INFO] [stdout] 139 |     let mut s = String::from("hello world");
[INFO] [stdout]     |         ----^
[INFO] [stdout]     |         |
[INFO] [stdout]     |         help: remove this `mut`
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(unused_mut)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field is never read: `number_of_friends`
[INFO] [stdout]    --> src/main.rs:164:9
[INFO] [stdout]     |
[INFO] [stdout] 164 |         number_of_friends: u32,
[INFO] [stdout]     |         ^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variant is never constructed: `NetworkError`
[INFO] [stdout]    --> src/main.rs:252:9
[INFO] [stdout]     |
[INFO] [stdout] 252 |         NetworkError,
[INFO] [stdout]     |         ^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variant is never constructed: `SerilizationError`
[INFO] [stdout]    --> src/main.rs:253:9
[INFO] [stdout]     |
[INFO] [stdout] 253 |         SerilizationError(String),
[INFO] [stdout]     |         ^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `closures`
[INFO] [stdout]    --> src/main.rs:310:4
[INFO] [stdout]     |
[INFO] [stdout] 310 | fn closures() {
[INFO] [stdout]     |    ^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable `className` should have a snake case name
[INFO] [stdout]    --> src/main.rs:264:41
[INFO] [stdout]     |
[INFO] [stdout] 264 |         RPCCallError::SerilizationError(className) => {
[INFO] [stdout]     |                                         ^^^^^^^^^ help: convert the identifier to snake case: `class_name`
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(non_snake_case)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 27 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 3.97s
[INFO] running `Command { std: "docker" "inspect" "9e0cb1d9cc5af953be6a23a35f505dd8159c00ed1686746e1be1ea65a12af28a", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "9e0cb1d9cc5af953be6a23a35f505dd8159c00ed1686746e1be1ea65a12af28a", kill_on_drop: false }`
[INFO] [stdout] 9e0cb1d9cc5af953be6a23a35f505dd8159c00ed1686746e1be1ea65a12af28a
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-20/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-20/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" "ghcr.io/rust-lang/crates-build-env/linux@sha256:5736fa189c1c60b01babf4b8b698fe57b6ecc41933a7ff2e0b8d7a221459412b" "/opt/rustwide/cargo-home/bin/cargo" "+a77da2d454e6caa227a85b16410b95f93495e7e0" "test" "--frozen" "--no-run" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 3d716faabe816066ab9ced48869b60ed2e758bd0bd9f9ff2846cb7fe8f614661
[INFO] running `Command { std: "docker" "start" "-a" "3d716faabe816066ab9ced48869b60ed2e758bd0bd9f9ff2846cb7fe8f614661", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling learn-rust v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: unnecessary trailing semicolon
[INFO] [stdout]    --> src/main.rs:200:6
[INFO] [stdout]     |
[INFO] [stdout] 200 |     };
[INFO] [stdout]     |      ^ help: remove this semicolon
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(redundant_semicolons)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused import: `std::*`
[INFO] [stdout]    --> src/main.rs:297:9
[INFO] [stdout]     |
[INFO] [stdout] 297 |     use std::*;         // glob import from Rust's standard library
[INFO] [stdout]     |         ^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(unused_imports)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unreachable pattern
[INFO] [stdout]    --> src/main.rs:269:9
[INFO] [stdout]     |
[INFO] [stdout] 269 | ...   _ => -1,    // _ is a placeholder that matches any value - if we put it as last, this will mean what the "default" label menas for ...
[INFO] [stdout]     |       ^
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(unreachable_patterns)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `x`
[INFO] [stdout]   --> src/main.rs:17:9
[INFO] [stdout]    |
[INFO] [stdout] 17 |     let x = 42;             // (type is inferred by the compiler whenever possible)
[INFO] [stdout]    |         ^ help: if this is intentional, prefix it with an underscore: `_x`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable `x` is assigned to, but never used
[INFO] [stdout]   --> src/main.rs:19:13
[INFO] [stdout]    |
[INFO] [stdout] 19 |     let mut x = 42;         // Now 'x' is declared to be mutable, thus...
[INFO] [stdout]    |             ^
[INFO] [stdout]    |
[INFO] [stdout]    = note: consider using `_x` instead
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: value assigned to `x` is never read
[INFO] [stdout]   --> src/main.rs:20:5
[INFO] [stdout]    |
[INFO] [stdout] 20 |     x = 21;                 // its value can be changed later on
[INFO] [stdout]    |     ^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_assignments)]` on by default
[INFO] [stdout]    = help: maybe it is overwritten before being read?
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `s`
[INFO] [stdout]   --> src/main.rs:40:13
[INFO] [stdout]    |
[INFO] [stdout] 40 |         let s = String::from("dynamically allocated string");           // s owns the allocated memory...
[INFO] [stdout]    |             ^ help: if this is intentional, prefix it with an underscore: `_s`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `y`
[INFO] [stdout]   --> src/main.rs:50:9
[INFO] [stdout]    |
[INFO] [stdout] 50 |     let y = x;          // a copy of the value of 'x'
[INFO] [stdout]    |         ^ help: if this is intentional, prefix it with an underscore: `_y`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `s4`
[INFO] [stdout]   --> src/main.rs:72:9
[INFO] [stdout]    |
[INFO] [stdout] 72 |     let s4 = gives_ownership();
[INFO] [stdout]    |         ^^ help: if this is intentional, prefix it with an underscore: `_s4`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `r1`
[INFO] [stdout]    --> src/main.rs:105:13
[INFO] [stdout]     |
[INFO] [stdout] 105 |         let r1 = &mut s1;
[INFO] [stdout]     |             ^^ help: if this is intentional, prefix it with an underscore: `_r1`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `r2`
[INFO] [stdout]    --> src/main.rs:110:9
[INFO] [stdout]     |
[INFO] [stdout] 110 |     let r2 = &s1;                   // but out of the scope of 'r1', we can create a reference again...
[INFO] [stdout]     |         ^^ help: if this is intentional, prefix it with an underscore: `_r2`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `r3`
[INFO] [stdout]    --> src/main.rs:111:9
[INFO] [stdout]     |
[INFO] [stdout] 111 |     let r3 = &s1;                   // ...even multiple immutable ones
[INFO] [stdout]     |         ^^ help: if this is intentional, prefix it with an underscore: `_r3`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: value assigned to `slice3` is never read
[INFO] [stdout]    --> src/main.rs:150:13
[INFO] [stdout]     |
[INFO] [stdout] 150 |     let mut slice3 = &s[1..6];
[INFO] [stdout]     |             ^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = help: maybe it is overwritten before being read?
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `slice4`
[INFO] [stdout]    --> src/main.rs:155:9
[INFO] [stdout]     |
[INFO] [stdout] 155 |     let slice4: &[i32];         // the type of each item must be 'i32'
[INFO] [stdout]     |         ^^^^^^ help: if this is intentional, prefix it with an underscore: `_slice4`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `red`
[INFO] [stdout]    --> src/main.rs:191:9
[INFO] [stdout]     |
[INFO] [stdout] 191 |     let red = RGBColor(0xff, 0x00, 0x00);
[INFO] [stdout]     |         ^^^ help: if this is intentional, prefix it with an underscore: `_red`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `foreign`
[INFO] [stdout]    --> src/main.rs:233:9
[INFO] [stdout]     |
[INFO] [stdout] 233 |     let foreign = IpAddress::V6(314159263, 123442);
[INFO] [stdout]     |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_foreign`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `some_ip`
[INFO] [stdout]    --> src/main.rs:238:9
[INFO] [stdout]     |
[INFO] [stdout] 238 |     let some_ip = Some(home);
[INFO] [stdout]     |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_some_ip`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `absent_ip`
[INFO] [stdout]    --> src/main.rs:240:9
[INFO] [stdout]     |
[INFO] [stdout] 240 |     let absent_ip: Option<IpAddress> = None; 
[INFO] [stdout]     |         ^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_absent_ip`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `x`
[INFO] [stdout]    --> src/main.rs:243:9
[INFO] [stdout]     |
[INFO] [stdout] 243 |     let x: i8 = 5;
[INFO] [stdout]     |         ^ help: if this is intentional, prefix it with an underscore: `_x`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `y`
[INFO] [stdout]    --> src/main.rs:244:9
[INFO] [stdout]     |
[INFO] [stdout] 244 |     let y: Option<i8> = Some(5);
[INFO] [stdout]     |         ^ help: if this is intentional, prefix it with an underscore: `_y`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `retcode`
[INFO] [stdout]    --> src/main.rs:259:9
[INFO] [stdout]     |
[INFO] [stdout] 259 |     let retcode = match error {     // match forces us to cover all possible cases
[INFO] [stdout]     |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_retcode`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable does not need to be mutable
[INFO] [stdout]    --> src/main.rs:139:9
[INFO] [stdout]     |
[INFO] [stdout] 139 |     let mut s = String::from("hello world");
[INFO] [stdout]     |         ----^
[INFO] [stdout]     |         |
[INFO] [stdout]     |         help: remove this `mut`
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(unused_mut)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field is never read: `number_of_friends`
[INFO] [stdout]    --> src/main.rs:164:9
[INFO] [stdout]     |
[INFO] [stdout] 164 |         number_of_friends: u32,
[INFO] [stdout]     |         ^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variant is never constructed: `NetworkError`
[INFO] [stdout]    --> src/main.rs:252:9
[INFO] [stdout]     |
[INFO] [stdout] 252 |         NetworkError,
[INFO] [stdout]     |         ^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variant is never constructed: `SerilizationError`
[INFO] [stdout]    --> src/main.rs:253:9
[INFO] [stdout]     |
[INFO] [stdout] 253 |         SerilizationError(String),
[INFO] [stdout]     |         ^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `closures`
[INFO] [stdout]    --> src/main.rs:310:4
[INFO] [stdout]     |
[INFO] [stdout] 310 | fn closures() {
[INFO] [stdout]     |    ^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable `className` should have a snake case name
[INFO] [stdout]    --> src/main.rs:264:41
[INFO] [stdout]     |
[INFO] [stdout] 264 |         RPCCallError::SerilizationError(className) => {
[INFO] [stdout]     |                                         ^^^^^^^^^ help: convert the identifier to snake case: `class_name`
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(non_snake_case)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 27 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished test [unoptimized + debuginfo] target(s) in 1.84s
[INFO] running `Command { std: "docker" "inspect" "3d716faabe816066ab9ced48869b60ed2e758bd0bd9f9ff2846cb7fe8f614661", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "3d716faabe816066ab9ced48869b60ed2e758bd0bd9f9ff2846cb7fe8f614661", kill_on_drop: false }`
[INFO] [stdout] 3d716faabe816066ab9ced48869b60ed2e758bd0bd9f9ff2846cb7fe8f614661
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-20/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-20/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" "ghcr.io/rust-lang/crates-build-env/linux@sha256:5736fa189c1c60b01babf4b8b698fe57b6ecc41933a7ff2e0b8d7a221459412b" "/opt/rustwide/cargo-home/bin/cargo" "+a77da2d454e6caa227a85b16410b95f93495e7e0" "test" "--frozen", kill_on_drop: false }`
[INFO] [stdout] 1ce1b76e0e21763a53d85f5dc60ba643c34b2732b0f9ddfb32559a65939fea88
[INFO] running `Command { std: "docker" "start" "-a" "1ce1b76e0e21763a53d85f5dc60ba643c34b2732b0f9ddfb32559a65939fea88", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr] warning: unnecessary trailing semicolon
[INFO] [stderr]    --> src/main.rs:200:6
[INFO] [stderr]     |
[INFO] [stderr] 200 |     };
[INFO] [stderr]     |      ^ help: remove this semicolon
[INFO] [stderr]     |
[INFO] [stderr]     = note: `#[warn(redundant_semicolons)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: unused import: `std::*`
[INFO] [stderr]    --> src/main.rs:297:9
[INFO] [stderr]     |
[INFO] [stderr] 297 |     use std::*;         // glob import from Rust's standard library
[INFO] [stderr]     |         ^^^^^^
[INFO] [stderr]     |
[INFO] [stderr]     = note: `#[warn(unused_imports)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: unreachable pattern
[INFO] [stderr]    --> src/main.rs:269:9
[INFO] [stderr]     |
[INFO] [stderr] 269 | ...   _ => -1,    // _ is a placeholder that matches any value - if we put it as last, this will mean what the "default" label menas for ...
[INFO] [stderr]     |       ^
[INFO] [stderr]     |
[INFO] [stderr]     = note: `#[warn(unreachable_patterns)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `x`
[INFO] [stderr]   --> src/main.rs:17:9
[INFO] [stderr]    |
[INFO] [stderr] 17 |     let x = 42;             // (type is inferred by the compiler whenever possible)
[INFO] [stderr]    |         ^ help: if this is intentional, prefix it with an underscore: `_x`
[INFO] [stderr]    |
[INFO] [stderr]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: variable `x` is assigned to, but never used
[INFO] [stderr]   --> src/main.rs:19:13
[INFO] [stderr]    |
[INFO] [stderr] 19 |     let mut x = 42;         // Now 'x' is declared to be mutable, thus...
[INFO] [stderr]    |             ^
[INFO] [stderr]    |
[INFO] [stderr]    = note: consider using `_x` instead
[INFO] [stderr] 
[INFO] [stderr] warning: value assigned to `x` is never read
[INFO] [stderr]   --> src/main.rs:20:5
[INFO] [stderr]    |
[INFO] [stderr] 20 |     x = 21;                 // its value can be changed later on
[INFO] [stderr]    |     ^
[INFO] [stderr]    |
[INFO] [stderr]    = note: `#[warn(unused_assignments)]` on by default
[INFO] [stderr]    = help: maybe it is overwritten before being read?
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `s`
[INFO] [stderr]   --> src/main.rs:40:13
[INFO] [stderr]    |
[INFO] [stderr] 40 |         let s = String::from("dynamically allocated string");           // s owns the allocated memory...
[INFO] [stderr]    |             ^ help: if this is intentional, prefix it with an underscore: `_s`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `y`
[INFO] [stderr]   --> src/main.rs:50:9
[INFO] [stderr]    |
[INFO] [stderr] 50 |     let y = x;          // a copy of the value of 'x'
[INFO] [stderr]    |         ^ help: if this is intentional, prefix it with an underscore: `_y`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `s4`
[INFO] [stderr]   --> src/main.rs:72:9
[INFO] [stderr]    |
[INFO] [stderr] 72 |     let s4 = gives_ownership();
[INFO] [stderr]    |         ^^ help: if this is intentional, prefix it with an underscore: `_s4`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `r1`
[INFO] [stderr]    --> src/main.rs:105:13
[INFO] [stderr]     |
[INFO] [stderr] 105 |         let r1 = &mut s1;
[INFO] [stderr]     |             ^^ help: if this is intentional, prefix it with an underscore: `_r1`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `r2`
[INFO] [stderr]    --> src/main.rs:110:9
[INFO] [stderr]     |
[INFO] [stderr] 110 |     let r2 = &s1;                   // but out of the scope of 'r1', we can create a reference again...
[INFO] [stderr]     |         ^^ help: if this is intentional, prefix it with an underscore: `_r2`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `r3`
[INFO] [stderr]    --> src/main.rs:111:9
[INFO] [stderr]     |
[INFO] [stderr] 111 |     let r3 = &s1;                   // ...even multiple immutable ones
[INFO] [stderr]     |         ^^ help: if this is intentional, prefix it with an underscore: `_r3`
[INFO] [stderr] 
[INFO] [stderr] warning: value assigned to `slice3` is never read
[INFO] [stderr]    --> src/main.rs:150:13
[INFO] [stderr]     |
[INFO] [stderr] 150 |     let mut slice3 = &s[1..6];
[INFO] [stderr]     |             ^^^^^^
[INFO] [stderr]     |
[INFO] [stderr]     = help: maybe it is overwritten before being read?
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `slice4`
[INFO] [stderr]    --> src/main.rs:155:9
[INFO] [stderr]     |
[INFO] [stderr] 155 |     let slice4: &[i32];         // the type of each item must be 'i32'
[INFO] [stderr]     |         ^^^^^^ help: if this is intentional, prefix it with an underscore: `_slice4`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `red`
[INFO] [stderr]    --> src/main.rs:191:9
[INFO] [stderr]     |
[INFO] [stderr] 191 |     let red = RGBColor(0xff, 0x00, 0x00);
[INFO] [stderr]     |         ^^^ help: if this is intentional, prefix it with an underscore: `_red`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `foreign`
[INFO] [stderr]    --> src/main.rs:233:9
[INFO] [stderr]     |
[INFO] [stderr] 233 |     let foreign = IpAddress::V6(314159263, 123442);
[INFO] [stderr]     |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_foreign`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `some_ip`
[INFO] [stderr]    --> src/main.rs:238:9
[INFO] [stderr]     |
[INFO] [stderr] 238 |     let some_ip = Some(home);
[INFO] [stderr]     |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_some_ip`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `absent_ip`
[INFO] [stderr]    --> src/main.rs:240:9
[INFO] [stderr]     |
[INFO] [stderr] 240 |     let absent_ip: Option<IpAddress> = None; 
[INFO] [stderr]     |         ^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_absent_ip`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `x`
[INFO] [stderr]    --> src/main.rs:243:9
[INFO] [stderr]     |
[INFO] [stderr] 243 |     let x: i8 = 5;
[INFO] [stderr]     |         ^ help: if this is intentional, prefix it with an underscore: `_x`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `y`
[INFO] [stderr]    --> src/main.rs:244:9
[INFO] [stderr]     |
[INFO] [stderr] 244 |     let y: Option<i8> = Some(5);
[INFO] [stderr]     |         ^ help: if this is intentional, prefix it with an underscore: `_y`
[INFO] [stderr] 
[INFO] [stderr] warning: unused variable: `retcode`
[INFO] [stderr]    --> src/main.rs:259:9
[INFO] [stderr]     |
[INFO] [stderr] 259 |     let retcode = match error {     // match forces us to cover all possible cases
[INFO] [stderr]     |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_retcode`
[INFO] [stderr] 
[INFO] [stderr] warning: variable does not need to be mutable
[INFO] [stderr]    --> src/main.rs:139:9
[INFO] [stderr]     |
[INFO] [stderr] 139 |     let mut s = String::from("hello world");
[INFO] [stderr]     |         ----^
[INFO] [stderr]     |         |
[INFO] [stderr]     |         help: remove this `mut`
[INFO] [stderr]     |
[INFO] [stderr]     = note: `#[warn(unused_mut)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: field is never read: `number_of_friends`
[INFO] [stderr]    --> src/main.rs:164:9
[INFO] [stderr]     |
[INFO] [stderr] 164 |         number_of_friends: u32,
[INFO] [stderr]     |         ^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr]     |
[INFO] [stderr]     = note: `#[warn(dead_code)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: variant is never constructed: `NetworkError`
[INFO] [stderr]    --> src/main.rs:252:9
[INFO] [stderr]     |
[INFO] [stderr] 252 |         NetworkError,
[INFO] [stderr]     |         ^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: variant is never constructed: `SerilizationError`
[INFO] [stderr]    --> src/main.rs:253:9
[INFO] [stderr]     |
[INFO] [stderr] 253 |         SerilizationError(String),
[INFO] [stderr]     |         ^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: function is never used: `closures`
[INFO] [stderr]    --> src/main.rs:310:4
[INFO] [stderr]     |
[INFO] [stderr] 310 | fn closures() {
[INFO] [stderr]     |    ^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: variable `className` should have a snake case name
[INFO] [stderr]    --> src/main.rs:264:41
[INFO] [stderr]     |
[INFO] [stderr] 264 |         RPCCallError::SerilizationError(className) => {
[INFO] [stderr]     |                                         ^^^^^^^^^ help: convert the identifier to snake case: `class_name`
[INFO] [stderr]     |
[INFO] [stderr]     = note: `#[warn(non_snake_case)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: `learn-rust` (bin "learn-rust" test) generated 27 warnings
[INFO] [stderr]     Finished test [unoptimized + debuginfo] target(s) in 23.46s
[INFO] [stderr]      Running unittests (/opt/rustwide/target/debug/deps/learn_rust-9523b7a48c5c310e)
[INFO] [stdout] 
[INFO] [stdout] running 0 tests
[INFO] [stdout] 
[INFO] [stdout] test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
[INFO] [stdout] 
[INFO] running `Command { std: "docker" "inspect" "1ce1b76e0e21763a53d85f5dc60ba643c34b2732b0f9ddfb32559a65939fea88", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "1ce1b76e0e21763a53d85f5dc60ba643c34b2732b0f9ddfb32559a65939fea88", kill_on_drop: false }`
[INFO] [stdout] 1ce1b76e0e21763a53d85f5dc60ba643c34b2732b0f9ddfb32559a65939fea88