[INFO] updating cached repository ruggeri/rust_learning
[INFO] running `"git" "fetch" "--all"`
[INFO] [stdout] Fetching origin
[INFO] [stderr] From git://github.com/ruggeri/rust_learning
[INFO] [stderr]  * branch            HEAD       -> FETCH_HEAD
[INFO] running `"git" "clone" "work/cache/sources/gh/ruggeri/rust_learning" "work/ex/pr-63376/sources/master#60960a260f7b5c695fd0717311d72ce62dd4eb43/gh/ruggeri/rust_learning"`
[INFO] [stderr] Cloning into 'work/ex/pr-63376/sources/master#60960a260f7b5c695fd0717311d72ce62dd4eb43/gh/ruggeri/rust_learning'...
[INFO] [stderr] done.
[INFO] running `"git" "clone" "work/cache/sources/gh/ruggeri/rust_learning" "work/ex/pr-63376/sources/try#266783e4e09e4e9d5307c1c8e695659c58bbcac7/gh/ruggeri/rust_learning"`
[INFO] [stderr] Cloning into 'work/ex/pr-63376/sources/try#266783e4e09e4e9d5307c1c8e695659c58bbcac7/gh/ruggeri/rust_learning'...
[INFO] [stderr] done.
[INFO] running `"git" "rev-parse" "HEAD"`
[INFO] [stdout] 6564c9e695a39cf690d74e0eb370d542f146007c
[INFO] sha for GitHub repo ruggeri/rust_learning: 6564c9e695a39cf690d74e0eb370d542f146007c
[INFO] validating manifest of ruggeri/rust_learning on toolchain master#60960a260f7b5c695fd0717311d72ce62dd4eb43
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+60960a260f7b5c695fd0717311d72ce62dd4eb43-alt" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] validating manifest of ruggeri/rust_learning on toolchain try#266783e4e09e4e9d5307c1c8e695659c58bbcac7
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+266783e4e09e4e9d5307c1c8e695659c58bbcac7-alt" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] started frobbing ruggeri/rust_learning
[INFO] finished frobbing ruggeri/rust_learning
[INFO] frobbed toml for ruggeri/rust_learning written to work/ex/pr-63376/sources/master#60960a260f7b5c695fd0717311d72ce62dd4eb43/gh/ruggeri/rust_learning/Cargo.toml
[INFO] started frobbing ruggeri/rust_learning
[INFO] finished frobbing ruggeri/rust_learning
[INFO] frobbed toml for ruggeri/rust_learning written to work/ex/pr-63376/sources/try#266783e4e09e4e9d5307c1c8e695659c58bbcac7/gh/ruggeri/rust_learning/Cargo.toml
[INFO] crate ruggeri/rust_learning already has a lockfile, it will not be regenerated
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+60960a260f7b5c695fd0717311d72ce62dd4eb43-alt" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+266783e4e09e4e9d5307c1c8e695659c58bbcac7-alt" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] checking ruggeri/rust_learning against try#266783e4e09e4e9d5307c1c8e695659c58bbcac7 for pr-63376
[INFO] running `"docker" "create" "-v" "/mnt/big/crater/work/local/target-dirs/pr-63376/worker-3/try#266783e4e09e4e9d5307c1c8e695659c58bbcac7:/opt/crater/target:rw,Z" "-v" "/mnt/big/crater/work/ex/pr-63376/sources/try#266783e4e09e4e9d5307c1c8e695659c58bbcac7/gh/ruggeri/rust_learning:/opt/crater/workdir:ro,Z" "-v" "/mnt/big/crater/work/local/cargo-home:/opt/crater/cargo-home:ro,Z" "-v" "/mnt/big/crater/work/local/rustup-home:/opt/crater/rustup-home:ro,Z" "-e" "USER_ID=1000" "-e" "SOURCE_DIR=/opt/crater/workdir" "-e" "MAP_USER_ID=1000" "-e" "CARGO_TARGET_DIR=/opt/crater/target" "-e" "CARGO_INCREMENTAL=0" "-e" "RUST_BACKTRACE=full" "-e" "RUSTFLAGS=--cap-lints=forbid" "-e" "CARGO_HOME=/opt/crater/cargo-home" "-e" "RUSTUP_HOME=/opt/crater/rustup-home" "-w" "/opt/crater/workdir" "-m" "1536M" "--network" "none" "rustops/crates-build-env" "/opt/crater/cargo-home/bin/cargo" "+266783e4e09e4e9d5307c1c8e695659c58bbcac7-alt" "check" "--frozen" "--all" "--all-targets"`
[INFO] [stdout] f3f4298bb3cc5897d8c163d514bc8b729df9cd208e06c2a9ff264776e9cf4ed3
[INFO] running `"docker" "start" "-a" "f3f4298bb3cc5897d8c163d514bc8b729df9cd208e06c2a9ff264776e9cf4ed3"`
[INFO] [stderr]     Checking rust_learning v0.1.0 (/opt/crater/workdir)
[INFO] [stderr] error[E0499]: cannot borrow `*self` as mutable more than once at a time
[INFO] [stderr]   --> src/bst/bst.rs:79:61
[INFO] [stderr]    |
[INFO] [stderr] 75 |       fn find_mut(&mut self, t: &T) -> &mut BST<T> {
[INFO] [stderr]    |                   - let's call the lifetime of this reference `'1`
[INFO] [stderr] 76 | /         match self {
[INFO] [stderr] 77 | |             Nil => self,
[INFO] [stderr] 78 | |             Node(NodeData { value, left, .. }) if *t < *value => left.find_mut(t),
[INFO] [stderr]    | |                                    ---- first mutable borrow occurs here
[INFO] [stderr] 79 | |             Node(NodeData { value, .. }) if *t == *value => self,
[INFO] [stderr]    | |                                                             ^^^^ second mutable borrow occurs here
[INFO] [stderr] 80 | |             Node(NodeData { value, right, .. }) if *value < *t => right.find_mut(t),
[INFO] [stderr] 81 | |             Node(_) => unreachable!(),
[INFO] [stderr] 82 | |         }
[INFO] [stderr]    | |_________- returning this value requires that `self.0.left` is borrowed for `'1`
[INFO] [stderr] 
[INFO] [stderr] warning: variable does not need to be mutable
[INFO] [stderr]    --> src/bst/bst.rs:146:21
[INFO] [stderr]     |
[INFO] [stderr] 146 |                 let mut prev_node = left.find_max_mut();
[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] error: aborting due to previous error
[INFO] [stderr] 
[INFO] [stderr] For more information about this error, try `rustc --explain E0499`.
[INFO] [stderr] error: Could not compile `rust_learning`.
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error[E0499]: cannot borrow `*self` as mutable more than once at a time
[INFO] [stderr]   --> src/bst/bst.rs:79:61
[INFO] [stderr]    |
[INFO] [stderr] 75 |       fn find_mut(&mut self, t: &T) -> &mut BST<T> {
[INFO] [stderr]    |                   - let's call the lifetime of this reference `'1`
[INFO] [stderr] 76 | /         match self {
[INFO] [stderr] 77 | |             Nil => self,
[INFO] [stderr] 78 | |             Node(NodeData { value, left, .. }) if *t < *value => left.find_mut(t),
[INFO] [stderr]    | |                                    ---- first mutable borrow occurs here
[INFO] [stderr] 79 | |             Node(NodeData { value, .. }) if *t == *value => self,
[INFO] [stderr]    | |                                                             ^^^^ second mutable borrow occurs here
[INFO] [stderr] 80 | |             Node(NodeData { value, right, .. }) if *value < *t => right.find_mut(t),
[INFO] [stderr] 81 | |             Node(_) => unreachable!(),
[INFO] [stderr] 82 | |         }
[INFO] [stderr]    | |_________- returning this value requires that `self.0.left` is borrowed for `'1`
[INFO] [stderr] 
[INFO] [stderr] warning: variable does not need to be mutable
[INFO] [stderr]    --> src/bst/bst.rs:146:21
[INFO] [stderr]     |
[INFO] [stderr] 146 |                 let mut prev_node = left.find_max_mut();
[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] error: aborting due to previous error
[INFO] [stderr] 
[INFO] [stderr] For more information about this error, try `rustc --explain E0499`.
[INFO] [stderr] error: Could not compile `rust_learning`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `"docker" "inspect" "f3f4298bb3cc5897d8c163d514bc8b729df9cd208e06c2a9ff264776e9cf4ed3"`
[INFO] running `"docker" "rm" "-f" "f3f4298bb3cc5897d8c163d514bc8b729df9cd208e06c2a9ff264776e9cf4ed3"`
[INFO] [stdout] f3f4298bb3cc5897d8c163d514bc8b729df9cd208e06c2a9ff264776e9cf4ed3