[INFO] updating cached repository https://github.com/a74946443/learn_rust
[INFO] running `"git" "-c" "credential.helper=" "-c" "credential.helper=/mnt/big/crater/work/cargo-home/bin/git-credential-null" "-c" "remote.origin.fetch=refs/heads/*:refs/heads/*" "fetch" "origin" "--force" "--prune"`
[INFO] [stderr] From https://github.com/a74946443/learn_rust
[INFO] [stderr]    a9d0774..d622cf5  master     -> master
[INFO] running `"git" "rev-parse" "HEAD"`
[INFO] [stdout] d622cf5c15ac6aa7a0935afbcd649c11d6951aaa
[INFO] checking a74946443/learn_rust against master#c9edc02e8320a9e5799d185910ece7d491f524e6 for pr-64398
[INFO] running `"git" "clone" "work/cache/git-repos/https%3A%2F%2Fgithub.com%2Fa74946443%2Flearn_rust" "work/builds/worker-4/source"`
[INFO] [stderr] Cloning into 'work/builds/worker-4/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/a74946443/learn_rust on toolchain c9edc02e8320a9e5799d185910ece7d491f524e6-alt
[INFO] running `"/mnt/big/crater/work/cargo-home/bin/cargo" "+c9edc02e8320a9e5799d185910ece7d491f524e6-alt" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] started tweaking git repo https://github.com/a74946443/learn_rust
[INFO] finished tweaking git repo https://github.com/a74946443/learn_rust
[INFO] tweaked toml for git repo https://github.com/a74946443/learn_rust written to work/builds/worker-4/source/Cargo.toml
[INFO] crate git repo https://github.com/a74946443/learn_rust already has a lockfile, it will not be regenerated
[INFO] running `"/mnt/big/crater/work/cargo-home/bin/cargo" "+c9edc02e8320a9e5799d185910ece7d491f524e6-alt" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] running `"docker" "create" "-v" "/mnt/big/crater/work/builds/worker-4/target:/opt/rustwide/target:rw,Z" "-v" "/mnt/big/crater/work/builds/worker-4/source:/opt/rustwide/workdir:ro,Z" "-v" "/mnt/big/crater/work/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/mnt/big/crater/work/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "MAP_USER_ID=1000" "-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" "--network" "none" "rustops/crates-build-env" "/opt/rustwide/cargo-home/bin/cargo" "+c9edc02e8320a9e5799d185910ece7d491f524e6-alt" "check" "--frozen" "--all" "--all-targets"`
[INFO] [stdout] 9f8a91e67234f792ea162534766c4a56e99b70b9bb4f378770d5f0054f9620cb
[INFO] running `"docker" "start" "-a" "9f8a91e67234f792ea162534766c4a56e99b70b9bb4f378770d5f0054f9620cb"`
[INFO] [stderr]     Checking learn_rust v0.1.0 (/opt/rustwide/workdir)
[INFO] [stderr] warning: value assigned to `idx` is never read
[INFO] [stderr]   --> src/exercise/convert.rs:18:21
[INFO] [stderr]    |
[INFO] [stderr] 18 |             let mut idx:usize = 0;
[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: function is never used: `long_new`
[INFO] [stderr]  --> src/exercise/longest_palindrome.rs:2:1
[INFO] [stderr]   |
[INFO] [stderr] 2 | fn long_new(s: String) ->String {
[INFO] [stderr]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr]   |
[INFO] [stderr]   = note: `#[warn(dead_code)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: function is never used: `convert1`
[INFO] [stderr]   --> src/exercise/convert.rs:45:1
[INFO] [stderr]    |
[INFO] [stderr] 45 | fn convert1(s: String, num_rows: i32) -> String {
[INFO] [stderr]    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] warning: value assigned to `idx` is never read
[INFO] [stderr]   --> src/exercise/convert.rs:18:21
[INFO] [stderr]    |
[INFO] [stderr] 18 |             let mut idx:usize = 0;
[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: function is never used: `long_new`
[INFO] [stderr]  --> src/exercise/longest_palindrome.rs:2:1
[INFO] [stderr]   |
[INFO] [stderr] 2 | fn long_new(s: String) ->String {
[INFO] [stderr]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr]   |
[INFO] [stderr]   = note: `#[warn(dead_code)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: function is never used: `convert1`
[INFO] [stderr]   --> src/exercise/convert.rs:45:1
[INFO] [stderr]    |
[INFO] [stderr] 45 | fn convert1(s: String, num_rows: i32) -> String {
[INFO] [stderr]    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] error[E0432]: unresolved import `learn_rust::exercise::length_of_longest_substring::substring`
[INFO] [stderr]   --> tests/exercise.rs:16:9
[INFO] [stderr]    |
[INFO] [stderr] 16 |     use learn_rust::exercise::length_of_longest_substring::substring;
[INFO] [stderr]    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `substring` in `exercise::length_of_longest_substring`
[INFO] [stderr] 
[INFO] [stderr] error: aborting due to previous error
[INFO] [stderr] 
[INFO] [stderr] For more information about this error, try `rustc --explain E0432`.
[INFO] [stderr] error: Could not compile `learn_rust`.
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error: build failed
[INFO] running `"docker" "inspect" "9f8a91e67234f792ea162534766c4a56e99b70b9bb4f378770d5f0054f9620cb"`
[INFO] running `"docker" "rm" "-f" "9f8a91e67234f792ea162534766c4a56e99b70b9bb4f378770d5f0054f9620cb"`
[INFO] [stdout] 9f8a91e67234f792ea162534766c4a56e99b70b9bb4f378770d5f0054f9620cb