no-bare-casts

# No bare `as` casts Any bare `as` in production TypeScript is a signal to stop and work through the decision tree below. Test files (`*.test.ts`, `*.test-d.ts`, `test/**/*.ts`) are exempt — tests use `as` for stubbing and type assertions and that's fine. ## Decision tree Work through these in order before writing or keeping a cast: 1. **Tighten the input type.** Can the parameter, generic bound, or return type at the source be made more specific so the cast is unnecessary? 2. **Add a runtime check.** Can a type predicate (`function isUser(x): x is User`) narrow the type at runtime, eliminating the cast? 3. **Restructure a generic.** Can a bound or constraint carry the needed information, making the cast unnecessary? 4. **Use `satisfies`.** `expr satisfies T` checks the type without coercing it and is unaffected by this rule. Prefer it when you want a type-check, not a coercion. 5. **Use `castAs<T>(value)`.** When the value already satisfies `T` and the assertion is purely declarative, `castAs` is the right form. 6. **Only if none of the above: use `blindCast<T, "Reason">(value)`.** The `Reason` literal must name the specific compromise in language a reviewer can evaluate. ## Import ```typescript import { blindCast, castAs } from '@prisma-next/utils/casts'; ``` ## Helper signatures ```typescript // Escape hatch — the value is genuinely opaque or unrelated to the target type. // The Reason literal documents the compromise; the reviewer evaluates it. function blindCast<TargetType, Reason extends string>(input: unknown): TargetType // Declarative assertion — the value already satisfies T at runtime. function castAs<T>(value: T): T ``` ## The `Reason` bar `blindCast` is the auditable escape hatch of last resort — not a convenience wrapper. Reach for it only after the decision tree above has been exhausted. The second type argument must be a string literal that a reviewer can act on: ```typescript // ✅ Names the specific constraint blindCast<User, "deserialized from contract validator; shape has already been checked">(raw) // ❌ Adds no information — reviewer has nothing to evaluate blindCast<User, "trust me">(raw) ``` A vague reason is the reviewer's signal to push back and the author's signal to revisit the type design. ## "Convert when you touch" When you touch a file that contains a bare `as` cast — even as part of unrelated work — convert it to one of the accepted forms or eliminate it. The CI ratchet (`pnpm lint:casts`) rejects per-PR cast-count increases; converting on contact is how the total comes down over time.