[INFO] cloning 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" "clone" "--bare" "https://github.com/ruggeri/rust_learning" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fruggeri%2Frust_learning", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fruggeri%2Frust_learning'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 6564c9e695a39cf690d74e0eb370d542f146007c
[INFO] checking ruggeri/rust_learning against master#5a8a44196b3cf099f8c9b0156bd902eaec0b4e5f for pr-87248
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fruggeri%2Frust_learning" "/workspace/builds/worker-3/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-3/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/ruggeri/rust_learning on toolchain 5a8a44196b3cf099f8c9b0156bd902eaec0b4e5f
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+5a8a44196b3cf099f8c9b0156bd902eaec0b4e5f" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", 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-3/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" "+5a8a44196b3cf099f8c9b0156bd902eaec0b4e5f" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-3/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-3/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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+5a8a44196b3cf099f8c9b0156bd902eaec0b4e5f" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 2bec5978fbdcf4ca712bfe662ef4f0ea86c5e20873b1c31b814cf9a313d2a257
[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" "2bec5978fbdcf4ca712bfe662ef4f0ea86c5e20873b1c31b814cf9a313d2a257", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "2bec5978fbdcf4ca712bfe662ef4f0ea86c5e20873b1c31b814cf9a313d2a257", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "2bec5978fbdcf4ca712bfe662ef4f0ea86c5e20873b1c31b814cf9a313d2a257", kill_on_drop: false }`
[INFO] [stdout] 2bec5978fbdcf4ca712bfe662ef4f0ea86c5e20873b1c31b814cf9a313d2a257
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-3/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-3/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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+5a8a44196b3cf099f8c9b0156bd902eaec0b4e5f" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 2533882e3e20840bdc0bce6c0c28688044d201ca9a177facbd8ffd3b5335bdb8
[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" "2533882e3e20840bdc0bce6c0c28688044d201ca9a177facbd8ffd3b5335bdb8", kill_on_drop: false }`
[INFO] [stderr]     Checking 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] [stderr] error: could not compile `rust_learning` due to 2 previous errors; 1 warning emitted
[INFO] [stdout] error: aborting due to previous error; 1 warning emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stdout] For more information about this error, try `rustc --explain E0499`.
[INFO] [stdout] 
[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: build failed
[INFO] running `Command { std: "docker" "inspect" "2533882e3e20840bdc0bce6c0c28688044d201ca9a177facbd8ffd3b5335bdb8", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "2533882e3e20840bdc0bce6c0c28688044d201ca9a177facbd8ffd3b5335bdb8", kill_on_drop: false }`
[INFO] [stdout] 2533882e3e20840bdc0bce6c0c28688044d201ca9a177facbd8ffd3b5335bdb8