[INFO] crate mapcomp 0.1.3 is already in cache
[INFO] extracting crate mapcomp 0.1.3 into work/ex/beta-1.38-1/sources/1.37.0/reg/mapcomp/0.1.3
[INFO] extracting crate mapcomp 0.1.3 into work/ex/beta-1.38-1/sources/beta-2019-08-13/reg/mapcomp/0.1.3
[INFO] validating manifest of mapcomp-0.1.3 on toolchain 1.37.0
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.37.0" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] validating manifest of mapcomp-0.1.3 on toolchain beta-2019-08-13
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-08-13" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] started frobbing mapcomp-0.1.3
[INFO] finished frobbing mapcomp-0.1.3
[INFO] frobbed toml for mapcomp-0.1.3 written to work/ex/beta-1.38-1/sources/1.37.0/reg/mapcomp/0.1.3/Cargo.toml
[INFO] started frobbing mapcomp-0.1.3
[INFO] finished frobbing mapcomp-0.1.3
[INFO] frobbed toml for mapcomp-0.1.3 written to work/ex/beta-1.38-1/sources/beta-2019-08-13/reg/mapcomp/0.1.3/Cargo.toml
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.37.0" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update"`
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-08-13" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update"`
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.37.0" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-08-13" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] testing mapcomp-0.1.3 against beta-2019-08-13 for beta-1.38-1
[INFO] running `"docker" "create" "-v" "/mnt/big/crater/work/local/target-dirs/beta-1.38-1/worker-2/beta-2019-08-13:/opt/crater/target:rw,Z" "-v" "/mnt/big/crater/work/ex/beta-1.38-1/sources/beta-2019-08-13/reg/mapcomp/0.1.3:/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" "+beta-2019-08-13" "build" "--frozen"`
[INFO] [stdout] f5915d1207cce5ecd49368e38e6126b741a2752c0a32b233ca8a98d4bc02741d
[INFO] running `"docker" "start" "-a" "f5915d1207cce5ecd49368e38e6126b741a2752c0a32b233ca8a98d4bc02741d"`
[INFO] [stderr]    Compiling mapcomp v0.1.3 (/opt/crater/workdir)
[INFO] [stderr] error[E0554]: `#![feature]` may not be used on the beta release channel
[INFO] [stderr]   --> src/lib.rs:50:1
[INFO] [stderr]    |
[INFO] [stderr] 50 | #![feature(generators, generator_trait)]
[INFO] [stderr]    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] error[E0599]: no method named `resume` found for type `G` in the current scope
[INFO] [stderr]   --> src/lib.rs:71:39
[INFO] [stderr]    |
[INFO] [stderr] 71 |         match unsafe { self.generator.resume() } {
[INFO] [stderr]    |                                       ^^^^^^
[INFO] [stderr]    |
[INFO] [stderr]    = help: items from traits can only be used if the type parameter is bounded by the trait
[INFO] [stderr] help: the following trait defines an item `resume`, perhaps you need to restrict type parameter `G` with it:
[INFO] [stderr]    |
[INFO] [stderr] 66 | impl<G: std::ops::Generator + ::std::ops::Generator> Iterator for GeneratorIterator<G> {
[INFO] [stderr]    |      ^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] error: aborting due to 2 previous errors
[INFO] [stderr] 
[INFO] [stderr] Some errors have detailed explanations: E0554, E0599.
[INFO] [stderr] For more information about an error, try `rustc --explain E0554`.
[INFO] [stderr] error: Could not compile `mapcomp`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `"docker" "inspect" "f5915d1207cce5ecd49368e38e6126b741a2752c0a32b233ca8a98d4bc02741d"`
[INFO] running `"docker" "rm" "-f" "f5915d1207cce5ecd49368e38e6126b741a2752c0a32b233ca8a98d4bc02741d"`
[INFO] [stdout] f5915d1207cce5ecd49368e38e6126b741a2752c0a32b233ca8a98d4bc02741d