Sample
CompareAndSwap and CompareAndDelete on syncmap.Map distinguish absent keys from stored nil values rather than treating absent keys as nil
sha256:bb4cbf8a68f1606db024e32344cb04fd7a29f9c7fb1815eb5b9f5019df273754
PUBLISHED
L3_CONTRACT_PASS
MIT-0
Execution evidence
Declared environment and signed verification runs are separated so you can see exactly what this sample proves.
Evidence basisSigned contract pass
Verification receipts1
Verification levelL3_CONTRACT_PASS
Declared environment
- Execution context
- go
- Operating system
- linux
- Architecture
- x64
- Runtime
- go
- Language
- go
- Package manager
- gomod
Verification-run environments
- Execution context
- go 1.26
- Operating system
- linux alpine · musl
- Architecture
- x64
- Runtime
- go 1.26
- Language
- go
- Package manager
- gomod
- Execution
- container · docker
CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · golang@1 · 2026-08-17
Case
- Goal
- CompareAndSwap and CompareAndDelete on syncmap.Map distinguish absent keys from stored nil values rather than treating absent keys as nil HOW
- Packages
-
golang.org/x/sync 0.22.0
- Environment
- go
- Created
- 2026-08-17T23:39:23Z
Commonly assumed
Calling CompareAndSwap with an old value of nil acts as an insert-if-absent operation by treating unassigned keys as having a nil value.
The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.
Contract
- CompareAndSwap on an absent key returns false when old is nil, but succeeds and returns true when the key was explicitly stored with nil
- CompareAndDelete returns false on absent keys when old is nil, and returns true only when the key was explicitly stored with nil
- Load and LoadAndDelete distinguish absent keys (loaded=false) from keys explicitly stored with nil (loaded=true)
- Swap overwrites any existing value and returns whether the key was previously present
- Passing an unhashable key type such as a slice panics at runtime with hash of unhashable type
- CompareAndDelete and CompareAndSwap panic when comparing against an existing value of identical incomparable slice type, but return false without panic when the stored type differs
Files
- NOTES.md
- csx.json
- go.mod
- go.sum
- syncmap_test.go
Download the source artifact (tar.gz)
Origin Seeder
csx-seed
Verification receipts
- go 1.26 · linux alpine/x64 · docker · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · golang@1 · 2026-08-17 · ed25519:d91480838ac982c9