[INFO] cloning repository https://github.com/yegor256/microstack
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/yegor256/microstack" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fyegor256%2Fmicrostack", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fyegor256%2Fmicrostack'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] b408d3eed60dae98844218eddf71534b79a4f56f
[INFO] checking yegor256/microstack against master#068609ce766e55d2e7371cd2a86143a6d7e8e2e4 for pr-138952
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fyegor256%2Fmicrostack" "/workspace/builds/worker-4-tc1/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-4-tc1/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/yegor256/microstack on toolchain 068609ce766e55d2e7371cd2a86143a6d7e8e2e4
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+068609ce766e55d2e7371cd2a86143a6d7e8e2e4" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking git repo https://github.com/yegor256/microstack
[INFO] finished tweaking git repo https://github.com/yegor256/microstack
[INFO] tweaked toml for git repo https://github.com/yegor256/microstack written to /workspace/builds/worker-4-tc1/source/Cargo.toml
[INFO] crate git repo https://github.com/yegor256/microstack already has a lockfile, it will not be regenerated
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+068609ce766e55d2e7371cd2a86143a6d7e8e2e4" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-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@sha256:4b26683ee3c49f365255c425c23003cbf4366de097804722c29c5bbbee3624d2" "/opt/rustwide/cargo-home/bin/cargo" "+068609ce766e55d2e7371cd2a86143a6d7e8e2e4" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 085050331b07c566ee20612a94bacd6782ba3baf2873a3453508fe3615db4ab5
[INFO] running `Command { std: "docker" "start" "-a" "085050331b07c566ee20612a94bacd6782ba3baf2873a3453508fe3615db4ab5", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "085050331b07c566ee20612a94bacd6782ba3baf2873a3453508fe3615db4ab5", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "085050331b07c566ee20612a94bacd6782ba3baf2873a3453508fe3615db4ab5", kill_on_drop: false }`
[INFO] [stdout] 085050331b07c566ee20612a94bacd6782ba3baf2873a3453508fe3615db4ab5
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4-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=forbid" "-e" "RUSTDOCFLAGS=--cap-lints=forbid" "-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@sha256:4b26683ee3c49f365255c425c23003cbf4366de097804722c29c5bbbee3624d2" "/opt/rustwide/cargo-home/bin/cargo" "+068609ce766e55d2e7371cd2a86143a6d7e8e2e4" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] ff75bc6003a9a7f2868ed444599dfb324e8321ca5b4f9ee849c4d0ddba2fb167
[INFO] running `Command { std: "docker" "start" "-a" "ff75bc6003a9a7f2868ed444599dfb324e8321ca5b4f9ee849c4d0ddba2fb167", kill_on_drop: false }`
[INFO] [stderr]    Compiling serde v1.0.193
[INFO] [stderr]     Checking microstack v0.0.0 (/opt/rustwide/workdir)
[INFO] [stdout] error: `#[must_use]` has no effect when applied to a provided trait method
[INFO] [stdout]   --> src/clone.rs:26:5
[INFO] [stdout]    |
[INFO] [stdout] 26 |     #[must_use]
[INFO] [stdout]    |     ^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout] note: the lint level is defined here
[INFO] [stdout]   --> src/lib.rs:41:9
[INFO] [stdout]    |
[INFO] [stdout] 41 | #![deny(warnings)]
[INFO] [stdout]    |         ^^^^^^^^
[INFO] [stdout]    = note: `#[deny(unused_attributes)]` implied by `#[deny(warnings)]`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: `#[must_use]` has no effect when applied to a provided trait method
[INFO] [stdout]   --> src/ctors.rs:27:5
[INFO] [stdout]    |
[INFO] [stdout] 27 |     #[must_use]
[INFO] [stdout]    |     ^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: `#[must_use]` has no effect when applied to a provided trait method
[INFO] [stdout]   --> src/iterators.rs:28:5
[INFO] [stdout]    |
[INFO] [stdout] 28 |     #[must_use]
[INFO] [stdout]    |     ^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: `#[must_use]` has no effect when applied to a provided trait method
[INFO] [stdout]   --> src/iterators.rs:56:5
[INFO] [stdout]    |
[INFO] [stdout] 56 |     #[must_use]
[INFO] [stdout]    |     ^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `microstack` (lib) due to 4 previous errors
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] running `Command { std: "docker" "inspect" "ff75bc6003a9a7f2868ed444599dfb324e8321ca5b4f9ee849c4d0ddba2fb167", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "ff75bc6003a9a7f2868ed444599dfb324e8321ca5b4f9ee849c4d0ddba2fb167", kill_on_drop: false }`
[INFO] [stdout] ff75bc6003a9a7f2868ed444599dfb324e8321ca5b4f9ee849c4d0ddba2fb167