# rust-lang/polonius

Defines the Rust borrow checker.

Repository: https://github.com/rust-lang/polonius
Canonical: https://ross.abutalabs.com/products/polonius
Language: Rust
License: Apache-2.0
License Family: permissive
Last push: 2026-08-17T12:55:41+00:00

## Health v2 (maintenance only)
Score: 67/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 98, release rhythm 8, longevity 100
- inputs: {"age_days": 3046, "days_push": 16, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1737, forks 85 (observed 2026-08-28T04:05:29.949995+00:00)

## What it is
Polonius is a core library from the Rust project that models and implements the Rust borrow checker analysis. It supports multiple algorithm implementations (Naive, DatafrogOpt, LocationInsensitive) that can be run on borrow-check facts extracted by rustc.

## Use cases
- experiment with alternative borrow checking algorithms for Rust
- analyze NLL borrow-check facts generated by rustc
- research dataflow analysis for ownership and borrowing
- compare performance of borrow checker implementations
- understand how the Rust borrow checker works

## When to choose
- you are doing compiler research on Rust's borrow checking
- you want to prototype or compare borrow-check analysis algorithms
- you need to run borrow-check analysis on rustc-generated NLL fact dumps

## When to avoid
- you want a production borrow checker for compiling Rust code (use rustc)
- you need a stable, documented API for embedding in other tools
- you are not working with Rust compiler internals

## Facets
- artifact type: library
- maturity: experimental
- function: compiler, parser, developer-tools
- domain: compilers, programming-languages, developer-tools
- platform: rust, cli, cross-platform
- tags: borrow-checker, rust-compiler, static-analysis, dataflow, nll, type-system

## Member repositories
- rust-lang/polonius (main) score 67

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:29.949995+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:30:39.109558+00:00, confidence not recorded.
  - readme: https://github.com/rust-lang/polonius (fetched 2026-08-28T04:05:29.949995+00:00, sha e7102175362d)
- Data as of 2026-08-30T08:39:29.467469+00:00.