#ice #rustc

app icemelter

Tool to minimize files that trigger internal compiler errors (ICEs)

6 releases

0.3.2 Jul 17, 2023
0.3.1 Apr 1, 2023
0.3.0 Mar 18, 2023
0.2.0 Mar 17, 2023
0.1.0 Mar 17, 2023

#1 in #test-case-reduction

Download history 2/week @ 2023-11-09 1/week @ 2023-11-16 13/week @ 2023-11-23 19/week @ 2023-11-30 5/week @ 2023-12-07 6/week @ 2023-12-14 12/week @ 2023-12-21 6/week @ 2023-12-28 8/week @ 2024-01-25 12/week @ 2024-02-01 7/week @ 2024-02-08 66/week @ 2024-02-15

93 downloads per month

MIT license

621 lines


Icemelter automates steps in debugging rustc internal compiler errors (ICEs).


  • Automatically minimizes files that cause the ICE (MCVEs)*
  • Runs cargo-bisect-rustc
  • rustfmts MCVEs if doing so keeps the ICE
  • Generates copy-pasteable Markdown reports
  • Optionally downloads MCVEs from Github

*It really works: Icemelter reduced a ~250 line file to just 4 lines in #107454.

More features are planned.


Icemelter works on standalone Rust files. If your file is named ice.rs, use it like so:

icemelter ice.rs

By default, the result is stored to melted.rs. A few helpful flags:

  • --output: Change where the output file is written
  • --bisect: Bisect the regression with cargo-bisect-rustc
  • --markdown: Output a copy-pasteable report

Here's an example that uses a different compiler and adds a flag:

icemelter ice.rs -- rustc +nightly --crate-type=lib

For more options, see --help.


From a release

Statically-linked Linux binaries are available on the releases page.

From crates.io

You can build a released version from crates.io. You'll need the Rust compiler and the Cargo build tool. rustup makes it very easy to obtain these. Then run:

cargo install icemelter

This will install binaries in ~/.cargo/bin by default.


To build from source, you'll need the Rust compiler and the Cargo build tool. rustup makes it very easy to obtain these. Then, get the source:

git clone https://github.com/langston-barrett/icemelter
cd icemelter

Finally, build everything:

cargo build --release

You can find binaries in target/release. Run tests with cargo test.

How it works

Icemelter's minimization capabilities are built on treereduce-rust.


~513K SLoC