[INFO] fetching crate preftool-dirs 0.2.0...
[INFO] testing preftool-dirs-0.2.0 against 1.75.0 for beta-1.76-1
[INFO] extracting crate preftool-dirs 0.2.0 into /workspace/builds/worker-2-tc1/source
[INFO] validating manifest of crates.io crate preftool-dirs 0.2.0 on toolchain 1.75.0
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+1.75.0" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking crates.io crate preftool-dirs 0.2.0
[INFO] finished tweaking crates.io crate preftool-dirs 0.2.0
[INFO] tweaked toml for crates.io crate preftool-dirs 0.2.0 written to /workspace/builds/worker-2-tc1/source/Cargo.toml
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+1.75.0" "generate-lockfile" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Updating crates.io index
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+1.75.0" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]  Downloading crates ...
[INFO] [stderr]   Downloaded slog-stdlog v3.0.5
[INFO] [stderr]   Downloaded caseless v0.2.1
[INFO] [stderr]   Downloaded dirs-sys v0.1.0
[INFO] [stderr]   Downloaded preftool v0.2.0
[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@sha256:2788e3201cd34a07e3172128adcd8b3090168a8e3bcc40d7c032b9dda1df7d1c" "/opt/rustwide/cargo-home/bin/cargo" "+1.75.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 30a0fd0c371661632bd65156d817c019230f0c1565ae2743144c7d955b2971f8
[INFO] running `Command { std: "docker" "start" "-a" "30a0fd0c371661632bd65156d817c019230f0c1565ae2743144c7d955b2971f8", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "30a0fd0c371661632bd65156d817c019230f0c1565ae2743144c7d955b2971f8", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "30a0fd0c371661632bd65156d817c019230f0c1565ae2743144c7d955b2971f8", kill_on_drop: false }`
[INFO] [stdout] 30a0fd0c371661632bd65156d817c019230f0c1565ae2743144c7d955b2971f8
[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=warn" "-e" "RUSTDOCFLAGS=--cap-lints=warn" "-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@sha256:2788e3201cd34a07e3172128adcd8b3090168a8e3bcc40d7c032b9dda1df7d1c" "/opt/rustwide/cargo-home/bin/cargo" "+1.75.0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] e7a9cf3b38bce7bb0ce98d6de52488c2988ddf1e6edb59e92ad7a76b54a5fa8e
[INFO] running `Command { std: "docker" "start" "-a" "e7a9cf3b38bce7bb0ce98d6de52488c2988ddf1e6edb59e92ad7a76b54a5fa8e", kill_on_drop: false }`
[INFO] [stderr]    Compiling memchr v2.7.1
[INFO] [stderr]    Compiling libc v0.2.151
[INFO] [stderr]    Compiling regex-syntax v0.8.2
[INFO] [stderr]    Compiling slog v2.7.0
[INFO] [stderr]    Compiling tinyvec_macros v0.1.1
[INFO] [stderr]    Compiling version_check v0.9.4
[INFO] [stderr]    Compiling gimli v0.28.1
[INFO] [stderr]    Compiling adler v1.0.2
[INFO] [stderr]    Compiling cfg-if v1.0.0
[INFO] [stderr]    Compiling arc-swap v1.6.0
[INFO] [stderr]    Compiling rustc-demangle v0.1.23
[INFO] [stderr]    Compiling log v0.4.20
[INFO] [stderr]    Compiling crossbeam v0.2.12
[INFO] [stderr]    Compiling bitflags v1.3.2
[INFO] [stderr]    Compiling tinyvec v1.6.0
[INFO] [stderr]    Compiling miniz_oxide v0.7.1
[INFO] [stderr]    Compiling log v0.3.9
[INFO] [stderr]    Compiling error-chain v0.12.4
[INFO] [stderr]    Compiling slog-scope v4.4.0
[INFO] [stderr]    Compiling aho-corasick v1.1.2
[INFO] [stderr]    Compiling object v0.32.2
[INFO] [stderr]    Compiling slog-stdlog v3.0.5
[INFO] [stderr]    Compiling cc v1.0.83
[INFO] [stderr]    Compiling dirs-sys v0.1.0
[INFO] [stderr]    Compiling unicode-normalization v0.1.22
[INFO] [stderr]    Compiling backtrace v0.3.69
[INFO] [stderr]    Compiling regex-automata v0.4.3
[INFO] [stderr]    Compiling addr2line v0.21.0
[INFO] [stderr]    Compiling regex v1.10.2
[INFO] [stderr]    Compiling caseless v0.2.1
[INFO] [stderr]    Compiling preftool v0.2.0
[INFO] [stderr]    Compiling preftool-dirs v0.2.0 (/opt/rustwide/workdir)
[INFO] [stdout] error: no rules expected the token `:`
[INFO] [stdout]   --> src/lib.rs:22:34
[INFO] [stdout]    |
[INFO] [stdout] 16 |   macro_rules! vec_opt {
[INFO] [stdout]    |   -------------------- when calling this macro
[INFO] [stdout] ...
[INFO] [stdout] 22 |       1 + vec_opt!(__count $($value:expr,)*)
[INFO] [stdout]    |                                    ^ no rules expected this token in macro call
[INFO] [stdout]    |
[INFO] [stdout]   ::: src/lin.rs:18:14
[INFO] [stdout]    |
[INFO] [stdout] 18 |     let dirs = vec_opt!(
[INFO] [stdout]    |  ______________-
[INFO] [stdout] 19 | |     // XDG config path
[INFO] [stdout] 20 | |     env::var_os("XDG_CONFIG_HOME")
[INFO] [stdout] 21 | |       .and_then(dirs_sys::is_absolute_path)
[INFO] [stdout] ...  |
[INFO] [stdout] 26 | |       .map(|home_dir| home_dir.join(".config").join(&application)),
[INFO] [stdout] 27 | |   );
[INFO] [stdout]    | |___- in this macro invocation
[INFO] [stdout]    |
[INFO] [stdout] note: while trying to match `,`
[INFO] [stdout]   --> src/lib.rs:21:22
[INFO] [stdout]    |
[INFO] [stdout] 21 |   (__count $_fst:expr, $($value:expr,)*) => {
[INFO] [stdout]    |                      ^
[INFO] [stdout]    = note: this error originates in the macro `vec_opt` (in Nightly builds, run with -Z macro-backtrace for more info)
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unnecessary trailing semicolon
[INFO] [stdout]    --> src/lib.rs:204:6
[INFO] [stdout]     |
[INFO] [stdout] 204 |     };
[INFO] [stdout]     |      ^ help: remove this semicolon
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(redundant_semicolons)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unnecessary trailing semicolon
[INFO] [stdout]    --> src/lib.rs:220:6
[INFO] [stdout]     |
[INFO] [stdout] 220 |     };
[INFO] [stdout]     |      ^ help: remove this semicolon
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]    --> src/lib.rs:262:60
[INFO] [stdout]     |
[INFO] [stdout] 262 |   fn serialize(&self, rec: &slog::Record, serializer: &mut slog::Serializer) -> slog::Result {
[INFO] [stdout]     |                                                            ^^^^^^^^^^^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]     = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
[INFO] [stdout]     = note: `#[warn(bare_trait_objects)]` on by default
[INFO] [stdout] help: use `dyn`
[INFO] [stdout]     |
[INFO] [stdout] 262 |   fn serialize(&self, rec: &slog::Record, serializer: &mut dyn slog::Serializer) -> slog::Result {
[INFO] [stdout]     |                                                            +++
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]    --> src/lib.rs:300:66
[INFO] [stdout]     |
[INFO] [stdout] 300 |     fn serialize(&self, rec: &Record, key: Key, serializer: &mut Serializer) -> Result {
[INFO] [stdout]     |                                                                  ^^^^^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]     = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
[INFO] [stdout] help: use `dyn`
[INFO] [stdout]     |
[INFO] [stdout] 300 |     fn serialize(&self, rec: &Record, key: Key, serializer: &mut dyn Serializer) -> Result {
[INFO] [stdout]     |                                                                  +++
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to previous error; 4 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `preftool-dirs` (lib) due to 2 previous errors; 4 warnings emitted
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] running `Command { std: "docker" "inspect" "e7a9cf3b38bce7bb0ce98d6de52488c2988ddf1e6edb59e92ad7a76b54a5fa8e", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "e7a9cf3b38bce7bb0ce98d6de52488c2988ddf1e6edb59e92ad7a76b54a5fa8e", kill_on_drop: false }`
[INFO] [stdout] e7a9cf3b38bce7bb0ce98d6de52488c2988ddf1e6edb59e92ad7a76b54a5fa8e
[INFO] testing preftool-dirs-0.2.0 against beta-2023-12-22 for beta-1.76-1
[INFO] extracting crate preftool-dirs 0.2.0 into /workspace/builds/worker-2-tc2/source
[INFO] validating manifest of crates.io crate preftool-dirs 0.2.0 on toolchain beta-2023-12-22
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+beta-2023-12-22" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking crates.io crate preftool-dirs 0.2.0
[INFO] finished tweaking crates.io crate preftool-dirs 0.2.0
[INFO] tweaked toml for crates.io crate preftool-dirs 0.2.0 written to /workspace/builds/worker-2-tc2/source/Cargo.toml
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+beta-2023-12-22" "generate-lockfile" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Updating crates.io index
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+beta-2023-12-22" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/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@sha256:2788e3201cd34a07e3172128adcd8b3090168a8e3bcc40d7c032b9dda1df7d1c" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2023-12-22" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 5298299a81086bf6a967fa4f0f7df97d089f044bf0c9f3faf20818fafb70aca2
[INFO] running `Command { std: "docker" "start" "-a" "5298299a81086bf6a967fa4f0f7df97d089f044bf0c9f3faf20818fafb70aca2", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "5298299a81086bf6a967fa4f0f7df97d089f044bf0c9f3faf20818fafb70aca2", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "5298299a81086bf6a967fa4f0f7df97d089f044bf0c9f3faf20818fafb70aca2", kill_on_drop: false }`
[INFO] [stdout] 5298299a81086bf6a967fa4f0f7df97d089f044bf0c9f3faf20818fafb70aca2
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/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=warn" "-e" "RUSTDOCFLAGS=--cap-lints=warn" "-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@sha256:2788e3201cd34a07e3172128adcd8b3090168a8e3bcc40d7c032b9dda1df7d1c" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2023-12-22" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 6434ec979e23001807ae78c94cfe152a4bbbe6f6ba1fb964a326cdee20d86636
[INFO] running `Command { std: "docker" "start" "-a" "6434ec979e23001807ae78c94cfe152a4bbbe6f6ba1fb964a326cdee20d86636", kill_on_drop: false }`
[INFO] [stderr]    Compiling memchr v2.7.1
[INFO] [stderr]    Compiling libc v0.2.151
[INFO] [stderr]    Compiling regex-syntax v0.8.2
[INFO] [stderr]    Compiling slog v2.7.0
[INFO] [stderr]    Compiling adler v1.0.2
[INFO] [stderr]    Compiling gimli v0.28.1
[INFO] [stderr]    Compiling tinyvec_macros v0.1.1
[INFO] [stderr]    Compiling version_check v0.9.4
[INFO] [stderr]    Compiling log v0.4.20
[INFO] [stderr]    Compiling cfg-if v1.0.0
[INFO] [stderr]    Compiling arc-swap v1.6.0
[INFO] [stderr]    Compiling rustc-demangle v0.1.23
[INFO] [stderr]    Compiling crossbeam v0.2.12
[INFO] [stderr]    Compiling bitflags v1.3.2
[INFO] [stderr]    Compiling tinyvec v1.6.0
[INFO] [stderr]    Compiling miniz_oxide v0.7.1
[INFO] [stderr]    Compiling log v0.3.9
[INFO] [stderr]    Compiling error-chain v0.12.4
[INFO] [stderr]    Compiling aho-corasick v1.1.2
[INFO] [stderr]    Compiling object v0.32.2
[INFO] [stderr]    Compiling slog-scope v4.4.0
[INFO] [stderr]    Compiling slog-stdlog v3.0.5
[INFO] [stderr]    Compiling unicode-normalization v0.1.22
[INFO] [stderr]    Compiling cc v1.0.83
[INFO] [stderr]    Compiling dirs-sys v0.1.0
[INFO] [stderr]    Compiling backtrace v0.3.69
[INFO] [stderr]    Compiling regex-automata v0.4.3
[INFO] [stderr]    Compiling addr2line v0.21.0
[INFO] [stderr]    Compiling regex v1.10.2
[INFO] [stderr]    Compiling caseless v0.2.1
[INFO] [stderr]    Compiling preftool v0.2.0
[INFO] [stderr]    Compiling preftool-dirs v0.2.0 (/opt/rustwide/workdir)
[INFO] [stdout] error: no rules expected the token `:`
[INFO] [stdout]   --> src/lib.rs:22:34
[INFO] [stdout]    |
[INFO] [stdout] 16 |   macro_rules! vec_opt {
[INFO] [stdout]    |   -------------------- when calling this macro
[INFO] [stdout] ...
[INFO] [stdout] 22 |       1 + vec_opt!(__count $($value:expr,)*)
[INFO] [stdout]    |                                    ^ no rules expected this token in macro call
[INFO] [stdout]    |
[INFO] [stdout]   ::: src/lin.rs:18:14
[INFO] [stdout]    |
[INFO] [stdout] 18 |     let dirs = vec_opt!(
[INFO] [stdout]    |  ______________-
[INFO] [stdout] 19 | |     // XDG config path
[INFO] [stdout] 20 | |     env::var_os("XDG_CONFIG_HOME")
[INFO] [stdout] 21 | |       .and_then(dirs_sys::is_absolute_path)
[INFO] [stdout] ...  |
[INFO] [stdout] 26 | |       .map(|home_dir| home_dir.join(".config").join(&application)),
[INFO] [stdout] 27 | |   );
[INFO] [stdout]    | |___- in this macro invocation
[INFO] [stdout]    |
[INFO] [stdout] note: while trying to match `,`
[INFO] [stdout]   --> src/lib.rs:21:22
[INFO] [stdout]    |
[INFO] [stdout] 21 |   (__count $_fst:expr, $($value:expr,)*) => {
[INFO] [stdout]    |                      ^
[INFO] [stdout]    = note: this error originates in the macro `vec_opt` (in Nightly builds, run with -Z macro-backtrace for more info)
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unnecessary trailing semicolon
[INFO] [stdout]    --> src/lib.rs:204:6
[INFO] [stdout]     |
[INFO] [stdout] 204 |     };
[INFO] [stdout]     |      ^ help: remove this semicolon
[INFO] [stdout]     |
[INFO] [stdout]     = note: `#[warn(redundant_semicolons)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unnecessary trailing semicolon
[INFO] [stdout]    --> src/lib.rs:220:6
[INFO] [stdout]     |
[INFO] [stdout] 220 |     };
[INFO] [stdout]     |      ^ help: remove this semicolon
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]    --> src/lib.rs:262:60
[INFO] [stdout]     |
[INFO] [stdout] 262 |   fn serialize(&self, rec: &slog::Record, serializer: &mut slog::Serializer) -> slog::Result {
[INFO] [stdout]     |                                                            ^^^^^^^^^^^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]     = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
[INFO] [stdout]     = note: `#[warn(bare_trait_objects)]` on by default
[INFO] [stdout] help: use `dyn`
[INFO] [stdout]     |
[INFO] [stdout] 262 |   fn serialize(&self, rec: &slog::Record, serializer: &mut dyn slog::Serializer) -> slog::Result {
[INFO] [stdout]     |                                                            +++
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]    --> src/lib.rs:300:66
[INFO] [stdout]     |
[INFO] [stdout] 300 |     fn serialize(&self, rec: &Record, key: Key, serializer: &mut Serializer) -> Result {
[INFO] [stdout]     |                                                                  ^^^^^^^^^^
[INFO] [stdout]     |
[INFO] [stdout]     = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]     = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
[INFO] [stdout] help: use `dyn`
[INFO] [stdout]     |
[INFO] [stdout] 300 |     fn serialize(&self, rec: &Record, key: Key, serializer: &mut dyn Serializer) -> Result {
[INFO] [stdout]     |                                                                  +++
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to 1 previous error; 4 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `preftool-dirs` (lib) due to 2 previous errors; 4 warnings emitted
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] running `Command { std: "docker" "inspect" "6434ec979e23001807ae78c94cfe152a4bbbe6f6ba1fb964a326cdee20d86636", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "6434ec979e23001807ae78c94cfe152a4bbbe6f6ba1fb964a326cdee20d86636", kill_on_drop: false }`
[INFO] [stdout] 6434ec979e23001807ae78c94cfe152a4bbbe6f6ba1fb964a326cdee20d86636
