Flyweight Generator

The Flyweight generator emits a typed cache for a partial value type. Generated code is reflection-free and has no runtime dependency on PatternKit.

Usage

using PatternKit.Generators.Flyweight;

[Flyweight(typeof(string), CacheTypeName = "GlyphCache", Capacity = 10_000, Eviction = FlyweightEviction.Lru)]
public readonly partial record struct Glyph(char Value)
{
    [FlyweightFactory]
    private static Glyph Create(string key) => new(key[0]);
}

The generated cache exposes Get, TryGet, and Clear. Cache hits return the existing value; misses invoke the annotated factory under a lock so the factory is called once per key.

Eviction

FlyweightEviction.None creates an unbounded cache. FlyweightEviction.Lru requires Capacity > 0 and evicts the least recently used key deterministically.

Diagnostics

• PKFLY001: flyweight type must be partial.
• PKFLY002: no factory method found.
• PKFLY003: multiple factory methods found.
• PKFLY004: factory signature invalid.
• PKFLY005: generated cache type name conflicts.
• PKFLY006: invalid eviction configuration.