[INFO] updating cached repository https://github.com/ruggeri/rust_learning
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "-c" "remote.origin.fetch=refs/heads/*:refs/heads/*" "fetch" "origin" "--force" "--prune", kill_on_drop: false }`
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 6564c9e695a39cf690d74e0eb370d542f146007c
[INFO] testing ruggeri/rust_learning against master#8534be72fc3b9c5f2f2dc4e4ee7b651a008e9a3e for pr-74409
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fruggeri%2Frust_learning" "/workspace/builds/worker-4/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-4/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/ruggeri/rust_learning on toolchain 8534be72fc3b9c5f2f2dc4e4ee7b651a008e9a3e
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+8534be72fc3b9c5f2f2dc4e4ee7b651a008e9a3e" "read-manifest" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] started tweaking git repo https://github.com/ruggeri/rust_learning
[INFO] finished tweaking git repo https://github.com/ruggeri/rust_learning
[INFO] tweaked toml for git repo https://github.com/ruggeri/rust_learning written to /workspace/builds/worker-4/source/Cargo.toml
[INFO] crate git repo https://github.com/ruggeri/rust_learning already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+8534be72fc3b9c5f2f2dc4e4ee7b651a008e9a3e" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/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" "MAP_USER_ID=0" "-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" "--network" "none" "rustops/crates-build-env@sha256:a636fd89d022f18117e1dc8fb37a0a009933cdbbe082814857f0e2024962d47c" "/opt/rustwide/cargo-home/bin/cargo" "+8534be72fc3b9c5f2f2dc4e4ee7b651a008e9a3e" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 67a4aaa8f80a69af78232d3701333c10f72045053a47eeaeca14536d10959996
[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" "67a4aaa8f80a69af78232d3701333c10f72045053a47eeaeca14536d10959996", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "67a4aaa8f80a69af78232d3701333c10f72045053a47eeaeca14536d10959996", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "67a4aaa8f80a69af78232d3701333c10f72045053a47eeaeca14536d10959996", kill_on_drop: false }`
[INFO] [stdout] 67a4aaa8f80a69af78232d3701333c10f72045053a47eeaeca14536d10959996
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/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" "MAP_USER_ID=0" "-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@sha256:a636fd89d022f18117e1dc8fb37a0a009933cdbbe082814857f0e2024962d47c" "/opt/rustwide/cargo-home/bin/cargo" "+8534be72fc3b9c5f2f2dc4e4ee7b651a008e9a3e" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] ae1e199a0e88bc4715955b75c14b5ef6a7c55deaa1da2ff432ffc5e4b736d43d
[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" "ae1e199a0e88bc4715955b75c14b5ef6a7c55deaa1da2ff432ffc5e4b736d43d", kill_on_drop: false }`
[INFO] [stderr]    Compiling rust_learning v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0499]: cannot borrow `*self` as mutable more than once at a time
[INFO] [stdout]   --> src/bst/bst.rs:79:61
[INFO] [stdout]    |
[INFO] [stdout] 75 |       fn find_mut(&mut self, t: &T) -> &mut BST<T> {
[INFO] [stdout]    |                   - let's call the lifetime of this reference `'1`
[INFO] [stdout] 76 | /         match self {
[INFO] [stdout] 77 | |             Nil => self,
[INFO] [stdout] 78 | |             Node(NodeData { value, left, .. }) if *t < *value => left.find_mut(t),
[INFO] [stdout]    | |                                    ---- first mutable borrow occurs here
[INFO] [stdout] 79 | |             Node(NodeData { value, .. }) if *t == *value => self,
[INFO] [stdout]    | |                                                             ^^^^ second mutable borrow occurs here
[INFO] [stdout] 80 | |             Node(NodeData { value, right, .. }) if *value < *t => right.find_mut(t),
[INFO] [stdout] 81 | |             Node(_) => unreachable!(),
[INFO] [stdout] 82 | |         }
[INFO] [stdout]    | |_________- returning this value requires that `self.0.left` is borrowed for `'1`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: variable does not need to be mutable
[INFO] [stdout]    --> src/bst/bst.rs:146:21
[INFO] [stdout]     |
[INFO] [stdout] 146 |                 let mut prev_node = left.find_max_mut();
[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] error: aborting due to previous error; 1 warning emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0499`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `rust_learning`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `Command { std: "docker" "inspect" "ae1e199a0e88bc4715955b75c14b5ef6a7c55deaa1da2ff432ffc5e4b736d43d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "ae1e199a0e88bc4715955b75c14b5ef6a7c55deaa1da2ff432ffc5e4b736d43d", kill_on_drop: false }`
[INFO] [stdout] ae1e199a0e88bc4715955b75c14b5ef6a7c55deaa1da2ff432ffc5e4b736d43d