Fix issues encountered in code you touch. No "pre-existing" exceptions.

Do it properly, not just simply. Correct architecture over quick hacks; no shortcuts or "good enough" solutions.

Type System

Dual Representation

• Type (external): boxed, Box<Type> for recursive children
• TypeData (internal): TypeId refs, O(1) equality via interning

Type Enum Variants

• Primitives: Int, Float, Bool, Str, Char, Byte, Unit, Never
• Special: Duration, Size
• Compound: Function, Tuple, List, Map, Set, Option, Result, Range, Channel
• Generic: Named, Applied, Var, Projection, ModuleNamespace
• Error: Error

Type Interning

• Sharded: 16 shards, FxHashMap<TypeData, u32> + Vec<TypeData> per shard
• Pre-interned: shard 0 indices 0-10 (Int, Float, Bool, Str, Char, Byte, Unit, Never, Duration, Size, Error)
• SharedTypeInterner: Arc<TypeInterner> with per-shard RwLock
• O(1) dedup: map lookup before insert

Inference Context

• InferenceContext: mutable state for unification
• TypeVar mapping: HashMap<TypeVar, Type>
• fresh_var(): counter-based generation
• Unification: structural with occurs check
• Generalization: free vars → quantified

Size Assertions

• static_assert_size! macro prevents enum bloat
• Type ≤ 40 bytes, TypeVar = 4 bytes

Salsa Compatibility

• All types: Clone, Eq, PartialEq, Hash, Debug
• No Arc<Mutex<T>> or function pointers

Key Files

| File | Purpose | |------|---------| | core.rs | Type enum, variants | | data.rs | TypeData (internal), TypeVar | | type_interner.rs | Interning, sharding | | context.rs | InferenceContext, unification |