hearth-case-class-rules

Hearth's CaseClass.parse API automates type class derivation for Scala case classes by applying encoder-style field reading and decoder-style construction patterns. It leverages primaryConstructor and field maps to eliminate manual boilerplate and generate type-safe instances.

Handling nested structures and existential types in Scala type class derivation requires advanced patterns like LambdaBuilder and cache-aware strategies. Using nest versus nestInCache ensures type-safe, cache-friendly derivations for complex nested case classes and mixed field types.

Yes, dual-path derivation with a runtime flag supports both fail-fast and error-accumulating workflows when constructing Scala case class instances. This allows decoders to either stop at the first error or collect all validation errors during field mapping.

Encoder-style derivation uses CaseClass.parse to read case class fields and extract data, while decoder-style construction uses primaryConstructor and field maps to build instances from decoded values. Both approaches minimize boilerplate but serve opposite data flow directions for type class instances.

Cache-aware derivation strategies like nestInCache are needed when deriving type class instances for nested Scala case classes or ADTs with repeated structures. These patterns prevent redundant derivation overhead and ensure efficient, reusable instances for complex existential types and mixed field types.