Skip to content

Defines the Rust borrow checker.

License

Apache-2.0, MIT licenses found

Licenses found

Apache-2.0
LICENSE-APACHE
MIT
LICENSE-MIT
Notifications You must be signed in to change notification settings

rust-lang/polonius

Folders and files

NameName
Last commit message
Last commit date
Jun 3, 2021
Mar 4, 2022
May 22, 2024
Aug 1, 2021
Aug 27, 2021
Jul 30, 2021
Jul 30, 2021
May 22, 2024
May 1, 2018
Aug 6, 2021
Aug 27, 2021
May 1, 2018
May 1, 2018
Dec 30, 2022
Aug 1, 2021
Nov 30, 2018
Mar 31, 2020

This is a core library that models the borrow check. It implements the analysis described in this blogpost and in this talk. Details are in the Polonius book.

Why the name "Polonius"?

The name comes from the famous quote "Neither a borrower nor a lender be", which comes from the character Polonius in Shakespeare's Hamlet.

Want to run the code?

One of the goals with this repo is to experiment and compare different implementations of the same algorithm. You can run the analysis by using cargo run and you can choose the analysis with -a. So for example to run against an example extract from clap, you might do:

> cargo +nightly run --release -- -a DatafrogOpt inputs/clap-rs/app-parser-{{impl}}-add_defaults/
    Finished release [optimized] target(s) in 0.05 secs
     Running `target/release/borrow-check 'inputs/clap-rs/app-parser-{{impl}}-add_defaults/'`
--------------------------------------------------
Directory: inputs/clap-rs/app-parser-{{impl}}-add_defaults/
Time: 3.856s

You could also try -a Naive to get the naive rules (more readable, slower) -- these are the exact rules described in the blogpost. You can also use -a LocationInsensitive to use a location insensitive analysis (faster, but may yield spurious errors).

By default, cargo run just prints timing. If you also want to see the results, try --show-tuples (which will show errors) and maybe -v (to show more intermediate computations). You can supply --help to get more docs.

How to generate your own inputs

To run the borrow checker on an input, you first need to generate the input facts. For that, you will need to run rustc with the -Znll-facts option:

> rustc -Znll-facts inputs/issue-47680/issue-47680.rs

Or, for generating the input facts of a crate using the #![feature(nll)] flag:

> cargo rustc -- -Znll-facts

This will generate a nll-facts directory with one subdirectory per function:

> ls -F nll-facts
{{impl}}-maybe_next/  main/

You can then run on these directories.