hearth-macro-basics

Type class derivation across Scala 2.13 and Scala 3 requires a unified macro architecture. Hearth provides a cross-version foundation using a DerivationCtx to bundle inputs, enabling context passing, caching, and rule-based generation for complex type structures.

Avoiding duplicate definitions during recursive macro derivation relies on caching. Hearth uses ValDefsCache and MLocal to store generated definitions, preventing redundant code generation and supporting safe recursive expansion for complex types.

Coordinating decision points in rule-based derivation macros requires a canonical rule order. Hearth enforces this ordering alongside safety checks to ensure consistent behavior and guide macro expansion across different modules.

Tracing macro decisions during type class generation requires dedicated logging. Hearth integrates MIO and Log utilities to record internal derivation choices, helping developers debug the rule-based generation pipeline and verify complex type structures.

Hearth supports scalable macro architectures through cross-module entry point patterns. It enables self-type skipping and placeholder caching within the DerivationCtx, allowing developers to build modular type class derivation systems without hitting compilation bottlenecks.