reincarnate

Appearance

Flash (AVM2 / ActionScript 3) ​

Status: Active — The first implemented target. The frontend, transform pipeline, and TypeScript runtime are all functional. Ongoing work focuses on output quality and API coverage.

Format ​

Flash applications are distributed as .swf files. SWF contains:

  • AVM2 bytecode — ActionScript 3 compiled to Adobe's ActionScript Virtual Machine 2
  • ABC (ActionScript Bytecode) — the bytecode container, embedded in DoABC tags
  • Assets — embedded images, audio, fonts, and binary data in typed tags
  • Display list — frame-by-frame timeline descriptions referencing symbol library entries

SWF is well-documented (SWF specification from Adobe, open-source parsers including Ruffle's swf crate).

Lifting Strategy ​

Full recompilation. The reincarnate-frontend-flash crate:

  1. Parses the SWF file (using the swf crate from Ruffle)
  2. Decodes ABC bytecode per class/method
  3. Emits typed IR — AS3 has full type annotations on locals, parameters, fields, and return types
  4. Identifies flash.* namespace boundaries (stdlib vs user code)

The replacement runtime in runtime/flash/ts/ implements the Flash API surface using Canvas 2D + Web Audio + DOM events.

Implementation Status ​

The pipeline is fully operational. Test project: ~/reincarnate/flash/cc/.

Frontend completeness ​

  • ✅ ABC bytecode decoding (all opcodes)
  • ✅ Class/interface/trait extraction
  • ✅ Type annotations from ABC metadata
  • ✅ Static method resolution, closure compilation
  • ✅ AVM2 int/uint semantics
  • ✅ CastKind (AsType vs Coerce), rest parameters
  • ⚠️ Exception handlers — from/to byte offsets extracted but no try/catch in IR yet
  • ⚠️ Class flags (is_sealed, is_final) — discarded
  • ⚠️ Protected namespace — per-class protected namespace not modeled
  • ⚠️ Trait metadata annotations ([Embed], [Bindable], custom) — discarded
  • ⚠️ override/final trait flags — discarded
  • ⚠️ DebugLine source line info — could enable source maps

Transform pass completeness ​

All passes implemented: TypeInference → ConstraintSolve → ConstantFolding → CfgSimplify → CoroutineLowering → Mem2Reg → ConstantFolding(2) → IntToBoolPromotion → RedCastElim → DCE.

Remaining quality issues:

  • ⚠️ Some while-loop bodies have unreachable code after continue
  • ⚠️ Structurizer occasionally inverts conditions (needs heuristic to match original polarity)
  • ⚠️ Inline closures: some fall back to $closureN field references when compile_closures() fails for dynamic features

Output quality ​

541 : any annotations in the cc test project (post-inference):

CategoryCountRoot cause
any[] arrays185No array element-type inference
Parameter : any186Untyped params from ABC metadata gaps
Return : any79Functions returning Dynamic
Field : any80Empty class defs, external supers
let locals11Block params with disagreeing arg types
const locals9Genuinely untyped from calls/block params

Runtime coverage ​

See API-COVERAGE-FLASH.md for full per-class/method tracking.

High-level gaps:

  • flash.display — 3D types (Matrix3D, Vector3D, PerspectiveProjection), Stage3D pipeline
  • flash.events — Touch/gesture events, NetStatusEvent, StageVideoEvent
  • flash.text.engine — TLF text block API (rarely used in games)
  • flash.net — Socket, XMLSocket, NetConnection/NetStream, LocalConnection
  • flash.system — System.gc/pause/resume, Worker/WorkerDomain
  • flash.utils — getTimer, setTimeout/setInterval
  • Top-level — Date, RegExp, XML (E4X), parseFloat/parseInt
  • flash.errors — All error subclasses (stubs needed)
  • flash.external — ExternalInterface

Known Limitations ​

  • AVM1 content (AS1/AS2 in old SWFs) is not supported and not planned
  • Stage3D (GPU-accelerated 3D pipeline) requires a WebGL/WebGPU backend — currently out of scope
  • Streaming — SWF streaming load semantics differ from static load; not modeled
  • Pixel fonts — Embedded bitmap fonts require glyph atlas extraction
  • Multi-typed locals — Some AS3 locals are assigned different types in different branches (e.g. sentinel 0.0 then string). These stay : any today; fixing requires SSA splitting, union types, or sentinel elimination

References ​