Sample

Downcast concrete error types and custom context through anyhow::Error without losing concrete types across Box trait object boundaries or Deref std::error::Error coercions

sha256:111c5fe00d1de4f527fc0ae3c444b12d048965ac957370eb4630a2a4a08b239f

Case

Goal

Downcast concrete error types and custom context through anyhow::Error without losing concrete types across Box trait object boundaries or Deref std::error::Error coercions HOW

Packages

anyhow 1.0.104

Environment

rust

Created

2026-08-16T07:54:47Z

Contract

• assert converting Box<dyn StdError> via from_boxed prevents recovering the concrete error with downcast_ref because TypeId tracks the boxed trait object
• assert converting a concrete StdError via From/into enables downcast_ref and is::<E>
• assert anyhow::Error::downcast_ref recursively searches through all attached context frames to find the root error
• assert std::error::Error::downcast_ref called via Deref on &dyn StdError fails on context-wrapped errors because std downcast does not traverse causes
• assert downcast_ref recovers custom context structs implementing Display and Debug even if they do not implement std::error::Error
• assert downcast_ref and downcast_mut on duplicate context types target the outermost most recently attached context frame
• assert downcast by value extracts the root error out of context layers, while mismatched downcast preserves the entire context chain intact
• assert context on Option None creates a root error with source None, whereas context on Result Err chains the previous error as source

Files

• Cargo.lock
• Cargo.toml
• NOTES.md
• csx.json
• src/lib.rs

Download the verified artifact (tar.gz) — the exact bytes the contract ran against

Origin Seeder

csx-seed

Verification receipts

• rust 1 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · cargo@1 · 2026-08-16 · ed25519:d91480838ac982c9