Sample
once_cell 1.21.4: Handle OnceCell try_insert (&T, T) error tuple return shape, Lazy into_value unevaluated Err(F) return, poison-free panic retry semantics, and &mut cell reset
Verified sample for cargo once_cell 1.21.4: Handle OnceCell try_insert (&T, T) error tuple return shape, Lazy into_value unevaluated Err(F) return…
sha256:606853390ed4aa0c8d86a36f2445430ec301faa64e65777b8f5770fd50e5ec46
This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured.
How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people.
MIT-0
Execution evidence
The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.
- Evidence basis
- Signed contract pass
- Verification receipts
- 2
- Signing keys that built it
- 2
Declared environment
rust linux x64 rust rust cargo
Verification-run environments
| Environment | Contract | Stages | Run |
|---|---|---|---|
| rust 1 · linux alpine/x64 · docker ed25519:d91480838ac982c9 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1 |
2026-08-16 |
| rust 1 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1 |
2026-08-18 |
Case
HOW- Goal
- Handle OnceCell try_insert (&T, T) error tuple return shape, Lazy into_value unevaluated Err(F) return, poison-free panic retry semantics, and &mut cell reset
- Packages
- Symbols
-
- once_cell::sync::OnceCell
- once_cell::sync::OnceCell::try_insert
- once_cell::sync::OnceCell::set
- once_cell::sync::OnceCell::get_mut
- once_cell::sync::OnceCell::take
- once_cell::sync::Lazy
- once_cell::sync::Lazy::into_value
- once_cell::sync::Lazy::get
- once_cell::sync::Lazy::force
- Environment
- rust
- Created
- 2026-08-16T08:09:37Z
Contract
- assert OnceCell::try_insert returns Ok(&T) on success and Err((&T, T)) with the existing reference and rejected value on collision instead of Err(T)
- assert OnceCell::set returns Result<(), T> without handing back a reference to the stored value
- assert Lazy::into_value on an uninitialized Lazy returns Err(F) without calling the initializer closure, and returns Ok(T) only after initialization
- assert Lazy::get returns None prior to forced evaluation without triggering the closure
- assert OnceCell does not become poisoned when get_or_init panics and allows subsequent initializations to retry and succeed
- assert OnceCell with &mut access can be modified in-place via get_mut and reset to empty via take for re-initialization
Files
- Cargo.lock
- Cargo.toml
- NOTES.md
- csx.json
- src/lib.rs
- tests/contract.rs