Check function calls for arity before argument inference
Calling a two-argument function with one argument crashes inference. Validate arity and check only supplied expressions safely.
- Focused work estimate
- 2h 15m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Type checking · Validation
Estimated field mix
- Compiler and language tooling100%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
Fictional rules editor Willow supports numbers, strings, booleans, records and functions in a deliberately small language. Define syntax and type rules locally; no arbitrary code execution is needed.
Setup prerequisites
- Create synthetic AST fixtures and a written type-rule table.
- Define source spans and structured diagnostic output.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Correct arity checks all arguments
- Wrong arity reports counts
- Nested argument errors remain inspectable
Implementation constraints
- Avoid fabricating missing AST nodes.
Verification to include
- Check valid call
- Call with too few and too many arguments
Deliverables
- Call checker and arity cases
Rollout and recovery
Disable call inference for malformed ASTs.
Value of the work
For the engineer: Practice type environments, unification and explainable rejection.
For the team: Inspect whether developer tooling catches mistakes without hiding uncertainty.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.