Scala refined — Refinement Types

Why it matters

Refined types add invariants to types. Understanding shapes type-safe Scala.

The architecture

Type: 'Int Refined Positive'.

Predicate part of type.

How it works end to end

Predicates: Positive, NonEmpty, MatchesRegex, etc.

Compile-time: refineMV for literals.

Runtime: refineV[Pred](value) returns Either.

Scala 3 alternative: iron.