[INFO] fetching crate bulls-and-cows 1.0.7...
[INFO] extracting crate bulls-and-cows 1.0.7 into work/ex/beta-1.37-6/sources/1.36.0/reg/bulls-and-cows/1.0.7
[INFO] extracting crate bulls-and-cows 1.0.7 into work/ex/beta-1.37-6/sources/beta-2019-07-23/reg/bulls-and-cows/1.0.7
[INFO] validating manifest of bulls-and-cows-1.0.7 on toolchain 1.36.0
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.36.0" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] validating manifest of bulls-and-cows-1.0.7 on toolchain beta-2019-07-23
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-07-23" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] started frobbing bulls-and-cows-1.0.7
[INFO] finished frobbing bulls-and-cows-1.0.7
[INFO] frobbed toml for bulls-and-cows-1.0.7 written to work/ex/beta-1.37-6/sources/1.36.0/reg/bulls-and-cows/1.0.7/Cargo.toml
[INFO] started frobbing bulls-and-cows-1.0.7
[INFO] finished frobbing bulls-and-cows-1.0.7
[INFO] frobbed toml for bulls-and-cows-1.0.7 written to work/ex/beta-1.37-6/sources/beta-2019-07-23/reg/bulls-and-cows/1.0.7/Cargo.toml
[INFO] crate bulls-and-cows-1.0.7 already has a lockfile, it will not be regenerated
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.36.0" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-07-23" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] testing bulls-and-cows-1.0.7 against 1.36.0 for beta-1.37-6
[INFO] running `"docker" "create" "-v" "/mnt/big/crater/work/local/target-dirs/beta-1.37-6/worker-2/1.36.0:/opt/crater/target:rw,Z" "-v" "/mnt/big/crater/work/ex/beta-1.37-6/sources/1.36.0/reg/bulls-and-cows/1.0.7:/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=warn" "-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" "+1.36.0" "build" "--frozen"`
[INFO] [stdout] 0c2e02e87ff4455dd261b9a58c9daed91e00849cf0b46a1d179bd0e14e6ccfcf
[INFO] running `"docker" "start" "-a" "0c2e02e87ff4455dd261b9a58c9daed91e00849cf0b46a1d179bd0e14e6ccfcf"`
[INFO] [stderr]    Compiling libc v0.2.50
[INFO] [stderr]    Compiling regex v1.1.2
[INFO] [stderr]    Compiling debug-helper v0.3.2
[INFO] [stderr]    Compiling permutohedron v0.2.4
[INFO] [stderr]    Compiling rand_chacha v0.1.1
[INFO] [stderr]    Compiling rand_pcg v0.1.2
[INFO] [stderr]    Compiling rand v0.6.5
[INFO] [stderr]    Compiling rand_jitter v0.1.3
[INFO] [stderr]    Compiling regex-syntax v0.6.5
[INFO] [stderr]    Compiling aho-corasick v0.6.10
[INFO] [stderr]    Compiling rand_os v0.1.3
[INFO] [stderr]    Compiling random-integer v1.0.2
[INFO] [stderr]    Compiling random-pick v1.2.3
[INFO] [stderr]    Compiling bulls-and-cows v1.0.7 (/opt/crater/workdir)
[INFO] [stderr] error: enum variants on type aliases are experimental
[INFO] [stderr]   --> src/host.rs:22:9
[INFO] [stderr]    |
[INFO] [stderr] 22 |         impl_debug_for_enum!(HostError::{LettersEmpty, AnswerLengthIncorrect, (AnswerContainsIncorrectLetter(_): (let .0 = "AnswerContainsIncorrectLetter")), (AnswerContainsDuplicatedLetter(_): (let .0 = "AnswerContainsDuplicatedLetter"))}, f, self);
[INFO] [stderr]    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr]    |
[INFO] [stderr]    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
[INFO] [stderr] 
[INFO] [stderr] error: enum variants on type aliases are experimental
[INFO] [stderr]   --> src/host.rs:22:9
[INFO] [stderr]    |
[INFO] [stderr] 22 |         impl_debug_for_enum!(HostError::{LettersEmpty, AnswerLengthIncorrect, (AnswerContainsIncorrectLetter(_): (let .0 = "AnswerContainsIncorrectLetter")), (AnswerContainsDuplicatedLetter(_): (let .0 = "AnswerContainsDuplicatedLetter"))}, f, self);
[INFO] [stderr]    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr]    |
[INFO] [stderr]    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
[INFO] [stderr] 
[INFO] [stderr] error: aborting due to 2 previous errors
[INFO] [stderr] 
[INFO] [stderr] error: Could not compile `bulls-and-cows`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `"docker" "inspect" "0c2e02e87ff4455dd261b9a58c9daed91e00849cf0b46a1d179bd0e14e6ccfcf"`
[INFO] running `"docker" "rm" "-f" "0c2e02e87ff4455dd261b9a58c9daed91e00849cf0b46a1d179bd0e14e6ccfcf"`
[INFO] [stdout] 0c2e02e87ff4455dd261b9a58c9daed91e00849cf0b46a1d179bd0e14e6ccfcf