[INFO] cloning repository https://github.com/ShivanshuKantPrasad/rust_by_example
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/ShivanshuKantPrasad/rust_by_example" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FShivanshuKantPrasad%2Frust_by_example", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FShivanshuKantPrasad%2Frust_by_example'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] dba9913c264c48bd545059608bdb9c0fe36da640
[INFO] checking ShivanshuKantPrasad/rust_by_example/dba9913c264c48bd545059608bdb9c0fe36da640 against master#ab869e094a907cc5d19b4080f22eccaf347f1f95 for pr-129604
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FShivanshuKantPrasad%2Frust_by_example" "/workspace/builds/worker-2-tc1/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-2-tc1/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/ShivanshuKantPrasad/rust_by_example on toolchain ab869e094a907cc5d19b4080f22eccaf347f1f95
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+ab869e094a907cc5d19b4080f22eccaf347f1f95" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking git repo https://github.com/ShivanshuKantPrasad/rust_by_example
[INFO] finished tweaking git repo https://github.com/ShivanshuKantPrasad/rust_by_example
[INFO] tweaked toml for git repo https://github.com/ShivanshuKantPrasad/rust_by_example written to /workspace/builds/worker-2-tc1/source/Cargo.toml
[INFO] crate git repo https://github.com/ShivanshuKantPrasad/rust_by_example 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" "+ab869e094a907cc5d19b4080f22eccaf347f1f95" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-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@sha256:923055f121b5182466d55868a8b05e67af8ba4a3a3f6bad814e953ca3cd3ac2a" "/opt/rustwide/cargo-home/bin/cargo" "+ab869e094a907cc5d19b4080f22eccaf347f1f95" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] a70b7768a2bdd6397844d8fa9784ae189c7a0edc536235a5b8dfadd1f8e81c86
[INFO] running `Command { std: "docker" "start" "-a" "a70b7768a2bdd6397844d8fa9784ae189c7a0edc536235a5b8dfadd1f8e81c86", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "a70b7768a2bdd6397844d8fa9784ae189c7a0edc536235a5b8dfadd1f8e81c86", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "a70b7768a2bdd6397844d8fa9784ae189c7a0edc536235a5b8dfadd1f8e81c86", kill_on_drop: false }`
[INFO] [stdout] a70b7768a2bdd6397844d8fa9784ae189c7a0edc536235a5b8dfadd1f8e81c86
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-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@sha256:923055f121b5182466d55868a8b05e67af8ba4a3a3f6bad814e953ca3cd3ac2a" "/opt/rustwide/cargo-home/bin/cargo" "+ab869e094a907cc5d19b4080f22eccaf347f1f95" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] c61f1d867387ff5e289df1438a1d874ff5eb2a879d09887f910bb779903bb5af
[INFO] running `Command { std: "docker" "start" "-a" "c61f1d867387ff5e289df1438a1d874ff5eb2a879d09887f910bb779903bb5af", kill_on_drop: false }`
[INFO] [stderr]     Checking rust_by_example v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: unused variable: `logical`
[INFO] [stdout]  --> src/bin/primitives.rs:2:9
[INFO] [stdout]   |
[INFO] [stdout] 2 |     let logical: bool = true;
[INFO] [stdout]   |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_logical`
[INFO] [stdout]   |
[INFO] [stdout]   = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `a_float`
[INFO] [stdout]  --> src/bin/primitives.rs:4:9
[INFO] [stdout]   |
[INFO] [stdout] 4 |     let a_float: f64 = 1.0;
[INFO] [stdout]   |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_a_float`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `an_integer`
[INFO] [stdout]  --> src/bin/primitives.rs:5:9
[INFO] [stdout]   |
[INFO] [stdout] 5 |     let an_integer = 5i32;
[INFO] [stdout]   |         ^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_an_integer`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `default_float`
[INFO] [stdout]  --> src/bin/primitives.rs:7:9
[INFO] [stdout]   |
[INFO] [stdout] 7 |     let default_float = 3.0;
[INFO] [stdout]   |         ^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_default_float`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `default_integer`
[INFO] [stdout]  --> src/bin/primitives.rs:8:9
[INFO] [stdout]   |
[INFO] [stdout] 8 |     let default_integer = 7;
[INFO] [stdout]   |         ^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_default_integer`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable `inferred_type` is assigned to, but never used
[INFO] [stdout]   --> src/bin/primitives.rs:10:13
[INFO] [stdout]    |
[INFO] [stdout] 10 |     let mut inferred_type = 12;
[INFO] [stdout]    |             ^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: consider using `_inferred_type` instead
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: value assigned to `inferred_type` is never read
[INFO] [stdout]   --> src/bin/primitives.rs:11:5
[INFO] [stdout]    |
[INFO] [stdout] 11 |     inferred_type = 4294967296i64;
[INFO] [stdout]    |     ^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = help: maybe it is overwritten before being read?
[INFO] [stdout]    = note: `#[warn(unused_assignments)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable `mutable` is assigned to, but never used
[INFO] [stdout]   --> src/bin/primitives.rs:13:13
[INFO] [stdout]    |
[INFO] [stdout] 13 |     let mut mutable = 12;
[INFO] [stdout]    |             ^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: consider using `_mutable` instead
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: value assigned to `mutable` is never read
[INFO] [stdout]   --> src/bin/primitives.rs:14:5
[INFO] [stdout]    |
[INFO] [stdout] 14 |     mutable = 21;
[INFO] [stdout]    |     ^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = help: maybe it is overwritten before being read?
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `mutable`
[INFO] [stdout]   --> src/bin/primitives.rs:20:9
[INFO] [stdout]    |
[INFO] [stdout] 20 |     let mutable = true;
[INFO] [stdout]    |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_mutable`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `x`
[INFO] [stdout]   --> src/bin/type_aliases.rs:20:9
[INFO] [stdout]    |
[INFO] [stdout] 20 |     let x = Operations::Add;
[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: 10 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variant `Subtract` is never constructed
[INFO] [stdout]  --> src/bin/type_aliases.rs:3:5
[INFO] [stdout]   |
[INFO] [stdout] 1 | enum VeryVerboseEnumOfThingsToDoWithNumbers {
[INFO] [stdout]   |      -------------------------------------- variant in this enum
[INFO] [stdout] 2 |     Add,
[INFO] [stdout] 3 |     Subtract,
[INFO] [stdout]   |     ^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: method `run` is never used
[INFO] [stdout]   --> src/bin/type_aliases.rs:10:8
[INFO] [stdout]    |
[INFO] [stdout] 9  | impl Operations {
[INFO] [stdout]    | --------------- method in this implementation
[INFO] [stdout] 10 |     fn run(&self, x: i32, y: i32) -> i32 {
[INFO] [stdout]    |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field `0` is never read
[INFO] [stdout]  --> src/bin/debug.rs:5:18
[INFO] [stdout]   |
[INFO] [stdout] 5 | struct Structure(String);
[INFO] [stdout]   |        --------- ^^^^^^
[INFO] [stdout]   |        |
[INFO] [stdout]   |        field in this struct
[INFO] [stdout]   |
[INFO] [stdout]   = help: consider removing this field
[INFO] [stdout]   = note: `Structure` 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: unused variable: `shdowed_binding`
[INFO] [stdout]   --> src/bin/shadowing.rs:14:9
[INFO] [stdout]    |
[INFO] [stdout] 14 |     let shdowed_binding = 2;
[INFO] [stdout]    |         ^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_shdowed_binding`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field `0` is never read
[INFO] [stdout]  --> src/bin/debug.rs:5:18
[INFO] [stdout]   |
[INFO] [stdout] 5 | struct Structure(String);
[INFO] [stdout]   |        --------- ^^^^^^
[INFO] [stdout]   |        |
[INFO] [stdout]   |        field in this struct
[INFO] [stdout]   |
[INFO] [stdout]   = help: consider removing this field
[INFO] [stdout]   = note: `Structure` 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: field `0` is never read
[INFO] [stdout]  --> src/bin/debug.rs:8:13
[INFO] [stdout]   |
[INFO] [stdout] 8 | struct Deep(Structure);
[INFO] [stdout]   |        ---- ^^^^^^^^^
[INFO] [stdout]   |        |
[INFO] [stdout]   |        field in this struct
[INFO] [stdout]   |
[INFO] [stdout]   = help: consider removing this field
[INFO] [stdout]   = note: `Deep` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 3 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: field `0` is never read
[INFO] [stdout]  --> src/bin/debug.rs:8:13
[INFO] [stdout]   |
[INFO] [stdout] 8 | struct Deep(Structure);
[INFO] [stdout]   |        ---- ^^^^^^^^^
[INFO] [stdout]   |        |
[INFO] [stdout]   |        field in this struct
[INFO] [stdout]   |
[INFO] [stdout]   = help: consider removing this field
[INFO] [stdout]   = note: `Deep` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 1 warning emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `noise_unused_variable`
[INFO] [stdout]   --> src/bin/variable_bindings.rs:14:9
[INFO] [stdout]    |
[INFO] [stdout] 14 |     let noise_unused_variable = 2u32;
[INFO] [stdout]    |         ^^^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_noise_unused_variable`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 1 warning emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `x`
[INFO] [stdout]   --> src/bin/type_aliases.rs:20:9
[INFO] [stdout]    |
[INFO] [stdout] 20 |     let x = Operations::Add;
[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: variant `Subtract` is never constructed
[INFO] [stdout]  --> src/bin/type_aliases.rs:3:5
[INFO] [stdout]   |
[INFO] [stdout] 1 | enum VeryVerboseEnumOfThingsToDoWithNumbers {
[INFO] [stdout]   |      -------------------------------------- variant in this enum
[INFO] [stdout] 2 |     Add,
[INFO] [stdout] 3 |     Subtract,
[INFO] [stdout]   |     ^^^^^^^^
[INFO] [stdout]   |
[INFO] [stdout]   = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: method `run` is never used
[INFO] [stdout]   --> src/bin/type_aliases.rs:10:8
[INFO] [stdout]    |
[INFO] [stdout] 9  | impl Operations {
[INFO] [stdout]    | --------------- method in this implementation
[INFO] [stdout] 10 |     fn run(&self, x: i32, y: i32) -> i32 {
[INFO] [stdout]    |        ^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 3 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `noise_unused_variable`
[INFO] [stdout]   --> src/bin/variable_bindings.rs:14:9
[INFO] [stdout]    |
[INFO] [stdout] 14 |     let noise_unused_variable = 2u32;
[INFO] [stdout]    |         ^^^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_noise_unused_variable`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 1 warning emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `shdowed_binding`
[INFO] [stdout]   --> src/bin/shadowing.rs:14:9
[INFO] [stdout]    |
[INFO] [stdout] 14 |     let shdowed_binding = 2;
[INFO] [stdout]    |         ^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_shdowed_binding`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 1 warning emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `logical`
[INFO] [stdout]  --> src/bin/primitives.rs:2:9
[INFO] [stdout]   |
[INFO] [stdout] 2 |     let logical: bool = true;
[INFO] [stdout]   |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_logical`
[INFO] [stdout]   |
[INFO] [stdout]   = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `a_float`
[INFO] [stdout]  --> src/bin/primitives.rs:4:9
[INFO] [stdout]   |
[INFO] [stdout] 4 |     let a_float: f64 = 1.0;
[INFO] [stdout]   |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_a_float`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `an_integer`
[INFO] [stdout]  --> src/bin/primitives.rs:5:9
[INFO] [stdout]   |
[INFO] [stdout] 5 |     let an_integer = 5i32;
[INFO] [stdout]   |         ^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_an_integer`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `default_float`
[INFO] [stdout]  --> src/bin/primitives.rs:7:9
[INFO] [stdout]   |
[INFO] [stdout] 7 |     let default_float = 3.0;
[INFO] [stdout]   |         ^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_default_float`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `default_integer`
[INFO] [stdout]  --> src/bin/primitives.rs:8:9
[INFO] [stdout]   |
[INFO] [stdout] 8 |     let default_integer = 7;
[INFO] [stdout]   |         ^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_default_integer`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable `inferred_type` is assigned to, but never used
[INFO] [stdout]   --> src/bin/primitives.rs:10:13
[INFO] [stdout]    |
[INFO] [stdout] 10 |     let mut inferred_type = 12;
[INFO] [stdout]    |             ^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: consider using `_inferred_type` instead
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: value assigned to `inferred_type` is never read
[INFO] [stdout]   --> src/bin/primitives.rs:11:5
[INFO] [stdout]    |
[INFO] [stdout] 11 |     inferred_type = 4294967296i64;
[INFO] [stdout]    |     ^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = help: maybe it is overwritten before being read?
[INFO] [stdout]    = note: `#[warn(unused_assignments)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable `mutable` is assigned to, but never used
[INFO] [stdout]   --> src/bin/primitives.rs:13:13
[INFO] [stdout]    |
[INFO] [stdout] 13 |     let mut mutable = 12;
[INFO] [stdout]    |             ^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: consider using `_mutable` instead
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: value assigned to `mutable` is never read
[INFO] [stdout]   --> src/bin/primitives.rs:14:5
[INFO] [stdout]    |
[INFO] [stdout] 14 |     mutable = 21;
[INFO] [stdout]    |     ^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = help: maybe it is overwritten before being read?
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `mutable`
[INFO] [stdout]   --> src/bin/primitives.rs:20:9
[INFO] [stdout]    |
[INFO] [stdout] 20 |     let mutable = true;
[INFO] [stdout]    |         ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_mutable`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 10 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.84s
[INFO] running `Command { std: "docker" "inspect" "c61f1d867387ff5e289df1438a1d874ff5eb2a879d09887f910bb779903bb5af", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "c61f1d867387ff5e289df1438a1d874ff5eb2a879d09887f910bb779903bb5af", kill_on_drop: false }`
[INFO] [stdout] c61f1d867387ff5e289df1438a1d874ff5eb2a879d09887f910bb779903bb5af