[INFO] crate gen-iter 0.1.2 is already in cache
[INFO] extracting crate gen-iter 0.1.2 into work/ex/beta-1.38-1/sources/1.37.0/reg/gen-iter/0.1.2
[INFO] extracting crate gen-iter 0.1.2 into work/ex/beta-1.38-1/sources/beta-2019-08-13/reg/gen-iter/0.1.2
[INFO] validating manifest of gen-iter-0.1.2 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 gen-iter-0.1.2 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 gen-iter-0.1.2
[INFO] finished frobbing gen-iter-0.1.2
[INFO] frobbed toml for gen-iter-0.1.2 written to work/ex/beta-1.38-1/sources/1.37.0/reg/gen-iter/0.1.2/Cargo.toml
[INFO] started frobbing gen-iter-0.1.2
[INFO] finished frobbing gen-iter-0.1.2
[INFO] frobbed toml for gen-iter-0.1.2 written to work/ex/beta-1.38-1/sources/beta-2019-08-13/reg/gen-iter/0.1.2/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] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.37.0" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-08-13" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] testing gen-iter-0.1.2 against 1.37.0 for beta-1.38-1
[INFO] running `"docker" "create" "-v" "/mnt/big/crater/work/local/target-dirs/beta-1.38-1/worker-5/1.37.0:/opt/crater/target:rw,Z" "-v" "/mnt/big/crater/work/ex/beta-1.38-1/sources/1.37.0/reg/gen-iter/0.1.2:/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" "+1.37.0" "build" "--frozen"`
[INFO] [stdout] a2290b9213dede5b36839dc447e10041491c2216a035efa65611f06ec8301c07
[INFO] running `"docker" "start" "-a" "a2290b9213dede5b36839dc447e10041491c2216a035efa65611f06ec8301c07"`
[INFO] [stderr]    Compiling gen-iter v0.1.2 (/opt/crater/workdir)
[INFO] [stderr] error[E0554]: #![feature] may not be used on the stable release channel
[INFO] [stderr]   --> src/lib.rs:37:1
[INFO] [stderr]    |
[INFO] [stderr] 37 | #![feature(generators, generator_trait)]
[INFO] [stderr]    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] error[E0599]: no method named `resume` found for type `T` in the current scope
[INFO] [stderr]   --> src/lib.rs:53:22
[INFO] [stderr]    |
[INFO] [stderr] 53 |         match self.0.resume() {
[INFO] [stderr]    |                      ^^^^^^
[INFO] [stderr]    |
[INFO] [stderr]    = help: items from traits can only be used if the trait is implemented and in scope
[INFO] [stderr]    = note: the following trait defines an item `resume`, perhaps you need to implement it:
[INFO] [stderr]            candidate #1: `std::ops::Generator`
[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 `gen-iter`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `"docker" "inspect" "a2290b9213dede5b36839dc447e10041491c2216a035efa65611f06ec8301c07"`
[INFO] running `"docker" "rm" "-f" "a2290b9213dede5b36839dc447e10041491c2216a035efa65611f06ec8301c07"`
[INFO] [stdout] a2290b9213dede5b36839dc447e10041491c2216a035efa65611f06ec8301c07