Module types 

Unified Type System

This module provides a unified type representation used across Pack:

• Design-time (parsing, validation)
• Runtime metadata (embedded in WASM packages)
• ABI encoding/decoding

Key design decisions:

• Arena as unified scoping structure
• Lexical scoping with qualified paths for cross-arena references
• Nominal typing - names are part of identity
• Unit is explicit - no more optional ok/err in Result
• Everything derives Hash - enables hash-based comparison
• Value kept as dynamic escape hatch

Structs

Arena

An arena containing type definitions, functions, and child arenas.

Case

A variant case.

Field

A record field.

Function

A function signature with parameters and results.

Param

A function parameter.

TypePath

A qualified path to a type.

Enums

Type

A type reference.

TypeDef

A type definition (named type).

Functions

sexpr_type

Helper to build an sexpr type (common use case).