[INFO] fetching crate singleton-attr 0.1.9...
[INFO] testing singleton-attr-0.1.9 against beta-2026-04-21 for beta-1.96-2
[INFO] extracting crate singleton-attr 0.1.9 into /workspace/builds/worker-2-tc2/source
[INFO] started tweaking crates.io crate singleton-attr 0.1.9
[INFO] removed 0 missing examples
[INFO] finished tweaking crates.io crate singleton-attr 0.1.9
[INFO] tweaked toml for crates.io crate singleton-attr 0.1.9 written to /workspace/builds/worker-2-tc2/source/Cargo.toml
[INFO] validating manifest of crates.io crate singleton-attr 0.1.9 on toolchain beta-2026-04-21
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+beta-2026-04-21" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] crate crates.io crate singleton-attr 0.1.9 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" "+beta-2026-04-21" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/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:d429b63d4308055ea97f60fb1d3dfca48854a00942f1bd2ad806beaf015945ec" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2026-04-21" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 4a97a0f6b19305a1784c43db3b58b12630c27f76ff2f00f67fe049b79e2b485f
[INFO] running `Command { std: "docker" "start" "-a" "4a97a0f6b19305a1784c43db3b58b12630c27f76ff2f00f67fe049b79e2b485f", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "4a97a0f6b19305a1784c43db3b58b12630c27f76ff2f00f67fe049b79e2b485f", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "4a97a0f6b19305a1784c43db3b58b12630c27f76ff2f00f67fe049b79e2b485f", kill_on_drop: false }`
[INFO] [stdout] 4a97a0f6b19305a1784c43db3b58b12630c27f76ff2f00f67fe049b79e2b485f
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2-tc2/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=warn" "-e" "RUSTDOCFLAGS=--cap-lints=warn" "-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:d429b63d4308055ea97f60fb1d3dfca48854a00942f1bd2ad806beaf015945ec" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2026-04-21" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] a023a832ab48b58a1780f71063a4b51bbbf3468d94f08c22cc318a7e1369cbc9
[INFO] running `Command { std: "docker" "start" "-a" "a023a832ab48b58a1780f71063a4b51bbbf3468d94f08c22cc318a7e1369cbc9", kill_on_drop: false }`
[INFO] [stderr]    Compiling syn v2.0.75
[INFO] [stderr]    Compiling singleton-attr-proc-macro v0.1.8
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the beta release channel
[INFO] [stdout]  --> /opt/rustwide/cargo-home/registry/src/index.crates.io-1949cf8c6b5b557f/singleton-attr-proc-macro-0.1.8/src/lib.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(proc_macro_span)]
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `singleton-attr-proc-macro` (lib) due to 1 previous error
[INFO] running `Command { std: "docker" "inspect" "a023a832ab48b58a1780f71063a4b51bbbf3468d94f08c22cc318a7e1369cbc9", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "a023a832ab48b58a1780f71063a4b51bbbf3468d94f08c22cc318a7e1369cbc9", kill_on_drop: false }`
[INFO] [stdout] a023a832ab48b58a1780f71063a4b51bbbf3468d94f08c22cc318a7e1369cbc9
