luawl/semantic-lifter

An IR Lifting Backend for Luau

Semantic-Lifter is a lifting backend for Luau made to validate, resolve, and restructure a typed intermediate representation into readable Luau that compiles under the official Luau compiler.

By separating frontend lifting from the core checks, the backend allows you to develop custom frontends for other Luau representations, each producing the same typed handoff, while reusing the unified checked pipeline.

This repository serves as the implementation of the forthcoming preprint "Checked, Not Trusted" and contains the backend, a source frontend, and a compiler-disassembly frontend.

To maintain clarity, everything is separated from one another. If you are new to Semantic-Lifter, please visit the links below:

• Getting Started & Introduction - Architecture overview, features, and short guides for building, lifting, and emitting.

To track active milestones, upcoming constructs, and the release of run records, visit our roadmap:

• Development Roadmap - Tracking of active milestones, upcoming constructs, solver work, and evidence publication.

Semantic-Lifter separates frontend lifting from the core backend pipeline, allowing new frontends to reuse the existing admission, checked resolution, structuring, and emission.

flowchart LR
    A["Luau Source / Disassembly Listing"]
        --> B["Frontend"]
        --> C["Typed Intermediate Representation (IR)"]
        --> D["Admission"]
        --> E["Checked Resolution"]
        --> F["Structuring"]
        --> G["Compile-Gated Emission"]
        --> H["Readable Luau"]

Each Semantic-Lifter build requires Zig and finds Lune, the Luau tools, and Node through build options or PATH.

Detailed building and testing instructions can be found here: Build and test.

Semantic-Lifter includes a PowerShell wrapper, build.ps1, for the common build and test invocations on Windows.

More information and usage examples can be found in build.ps1 and Build and test.

Every program that emit-luau publishes is first compiled by the official Luau compiler, and the conformance suite compiles every program it emits and checks what it computes. Two build steps, test and conformance, run every check.

The src directory contains the backend with its unit tests beside the sources.

• src/ - Backend and its unit tests

The luau directory contains the source frontend's tests and the conformance scripts, audits, and oracles that exercise the backend on its fixtures and generated programs.

• luau/ - Source frontend tests, conformance scripts, audits, and oracles
• luau/fixtures/ - Fixtures (Luau sources, manifests, and IR)

The frontends directory contains the compiler-disassembly frontend with its Node tests; the source frontend lives in luau/.

• frontends/disassembly/ - Compiler-disassembly frontend and adapter tests

An example lift of a Luau loop, with its emitted output, can be found in Example.

Command-line usage for both frontends is in Using Semantic-Lifter.

This repository implements the forthcoming preprint Checked, Not Trusted: Typed Evidence Contracts and Paired-Representation Testing for Luau Lifting Backends.

@misc{luawl2026semanticlifter,
  title  = {Checked, Not Trusted: Typed Evidence Contracts and Paired-Representation Testing for Luau Lifting Backends},
  author = {Luawl},
  year   = {2026},
  note   = {Preprint. Code: https://github.com/luawl/semantic-lifter},
}