This is a core library that models the borrow check. It implements the analysis
[described in this blogpost][post].
[post]: http://smallcultfollowing.com/babysteps/blog/2018/04/27/an-alias-based-formulation-of-the-borrow-checker/
### How to use
First off, you must use the **nightly** channel. To build, do something like this:
```bash
cargo +nightly build --release
```
You can try it on one our input tests like so:
```bash
cargo +nightly run --release -- inputs/issue-47680/nll-facts/main
```
This will generate a bunch of output tuples:
```
# borrow_live_at
"Mid(bb3[2])" "bw0"
"Mid(bb3[2])" "bw2"
"Mid(bb10[2])" "bw0"
...
```
### Want to see something slow?
One of the goals with this repo is to experiment and compare different
implementations of the same algorithm. The repo includes one
particularly egregious case where we currently perform poorly, and you
can test it against it like so:
```bash
> cargo +nightly run --release -- inputs/clap-rs/app-parser-{{impl}}-add_defaults/ | head
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: 113.316s
```
(You can see it is pretty dang slow on my machine!)
### 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
```
[PR #50370]: https://github.com/rust-lang/rust/pull/50370
This will generate a `nll-facts` directory with one subdirectory per function:
```bash
> ls -F nll-facts
{{impl}}-maybe_next/ main/
```
You can then run on these directories.