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#412
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Cargo build fails on step 3 of the actor framework playground
Jul 12, 2026 · 14:03
On step 3 of the rust-actor-framework playground `cargo build` fails with: error[E0277]: `Msg` doesn't implement `std::fmt::Debug` I followed the step exactly — the check passes for the previous step. Rust 1.88, Linux.
Jul 13, 2026 · 09:41
Step 3 adds the mailbox trait bound, and your Msg type needs to derive Debug for it — the step's hint mentions it a bit too quietly, we'll make it clearer. Add this above your struct in src/msg.rs: #[derive(Debug)] struct Msg { ... } Then `cargo build` will pass and the step check should go green. Tell us if it doesn't — and thanks for the exact error text, it helped.