What problem does it solve? Codebases often contain types that allow invalid states to be represented, leading to runtime bugs that could have been prevented at compile time. This Skill performs a static, read-only review of type designs to determine whether they make illegal states harder or impossible to represent. ## Core Features & Use Cases - Four-Dimension Evaluation: Assesses each type on encapsulation, invariant expression, invariant usefulness, and enforcement by the type system. - Evidence-Based Findings: Reports only actionable defects tied to a file, line, triggering condition, and observable impact, with concrete invalid-state examples instead of numeric scores. - Read-Only Review Boundary: Never edits files, executes code, or connects to databases; it checks callers and existing tests before reporting a gap. - Use Case: During a code review of a pull request introducing a new Order type, use this Skill to verify that states like "shipped but unpaid" are prevented at the type level rather than guarded only by runtime checks. ## Quick Start Ask the AI to review the type design of the types changed in this diff for encapsulation and invariant enforcement.
