[INFO] crate symbolics_calculus 0.1.5 is already in cache
[INFO] extracting crate symbolics_calculus 0.1.5 into work/ex/beta-1.38-1/sources/1.37.0/reg/symbolics_calculus/0.1.5
[INFO] extracting crate symbolics_calculus 0.1.5 into work/ex/beta-1.38-1/sources/beta-2019-08-13/reg/symbolics_calculus/0.1.5
[INFO] validating manifest of symbolics_calculus-0.1.5 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 symbolics_calculus-0.1.5 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 symbolics_calculus-0.1.5
[INFO] finished frobbing symbolics_calculus-0.1.5
[INFO] frobbed toml for symbolics_calculus-0.1.5 written to work/ex/beta-1.38-1/sources/1.37.0/reg/symbolics_calculus/0.1.5/Cargo.toml
[INFO] started frobbing symbolics_calculus-0.1.5
[INFO] finished frobbing symbolics_calculus-0.1.5
[INFO] frobbed toml for symbolics_calculus-0.1.5 written to work/ex/beta-1.38-1/sources/beta-2019-08-13/reg/symbolics_calculus/0.1.5/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 symbolics_calculus-0.1.5 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-1/1.37.0:/opt/crater/target:rw,Z" "-v" "/mnt/big/crater/work/ex/beta-1.38-1/sources/1.37.0/reg/symbolics_calculus/0.1.5:/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] 400293c7cc8e52df7e20a3df796a900657a363562c1640c3a3af2d882d8f4b72
[INFO] running `"docker" "start" "-a" "400293c7cc8e52df7e20a3df796a900657a363562c1640c3a3af2d882d8f4b72"`
[INFO] [stderr]    Compiling symbolics_core v0.1.5
[INFO] [stderr]    Compiling symbolics_calculus v0.1.5 (/opt/crater/workdir)
[INFO] [stderr] warning: unused imports: `apply`, `s`
[INFO] [stderr]  --> src/lib.rs:3:22
[INFO] [stderr]   |
[INFO] [stderr] 3 | use symbolics_core::{s, apply};
[INFO] [stderr]   |                      ^  ^^^^^
[INFO] [stderr]   |
[INFO] [stderr]   = note: #[warn(unused_imports)] on by default
[INFO] [stderr] 
[INFO] [stderr] error[E0283]: type annotations required: cannot resolve `std::string::String: std::convert::AsRef<_>`
[INFO] [stderr]   --> src/lib.rs:16:47
[INFO] [stderr]    |
[INFO] [stderr] 16 |             Add(a, b) => a.clone().deriv1(wrt.as_ref()) + b.clone().deriv1(wrt.as_ref()),
[INFO] [stderr]    |                                               ^^^^^^
[INFO] [stderr] 
[INFO] [stderr] error: aborting due to previous error
[INFO] [stderr] 
[INFO] [stderr] For more information about this error, try `rustc --explain E0283`.
[INFO] [stderr] error: Could not compile `symbolics_calculus`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `"docker" "inspect" "400293c7cc8e52df7e20a3df796a900657a363562c1640c3a3af2d882d8f4b72"`
[INFO] running `"docker" "rm" "-f" "400293c7cc8e52df7e20a3df796a900657a363562c1640c3a3af2d882d8f4b72"`
[INFO] [stdout] 400293c7cc8e52df7e20a3df796a900657a363562c1640c3a3af2d882d8f4b72