logos VS rustfmt

This is mighty impressive! I've been trying to get some motivation for the mythical rewrite of the proc macro in Logos, and this might just do it for me :D. I'll have a proper look later today and see if any of your findings have something that can be generalized. Also really surprised to see aarch64 doing better than x86_64 since the latter is what I've been optimizing for!

Rust is a very nice langage for implementing compilers, and has a nice ecosystem for it (logos, rust-peg, lalrpop, astmaker -- this one is mine --, etc...).

rust-langdev has a lot of libraries for building compilers in Rust. Perhaps you could use these to make your implementation easier, and revisit it later if you want to build things from scratch. I'd suggest logos for lexing, LALRPOP / chumsky for parsing, and rust-gc for garbage collection.

Thanks! For compile times you might find the CLI version that Andrew Hickman contributed useful, it's undocumented still mostly I fear but shouldn't be hard to use, see original PR: https://github.com/maciejhirsz/logos/pull/248

For my lexer generation purposes, I tend to use https://github.com/maciejhirsz/logos, as it not only generates an easy to use lazy lexer, but the result is also exceptionally fast!

Hi, I'm using rowan to create a parser and want to print more useful error messages with position in the text/file. I'm using logos (https://crates.io/crates/logos) to generate the lexer. Is there a way to get the starting and ending positions of a SyntaxToken? If not I thought of adding my own wrapper struct around the SyntaxTokens.

Is there a way for a lexer created with the logos crate (https://crates.io/crates/logos) to get the starting and ending positions for the tokens?

I wouldn't recommend Logos at this point. This recent bug is quite nasty and seems easy to hit, and the maintainer is unresponsive. Last commit was half a year ago. At this point I consider Logos abandonware, though it would be great if its development continued, or if it were forked.

logos uses "ridiculously fast".

The author provides very surface-level criticism of two Rust tools, but they don't look into why those choices were made.

With about five minutes of my time, I found out:

wrap_comments was introduced in 2019 [0]. There are bugs in the implementation (it breaks Markdown tables), so the option hasn't been marked as stable. Progress on the issue has been spotty.

--no-merge-sources is not trivial to re-implement [1]. The author has already explained why the flag no longer works -- Cargo integrated the command, but not all of the flags. This commit [2] explains why this functionality was removed in the first place.

Rust is open source, so the author of this blog post could improve the state of the software they care about by championing these issues. The --no-merge-sources error message even encourages you to open an issue, presumably so that the authors of Cargo can gauge the importance of certain flags/features.

You could even do something much simpler, like adding a comment to the related issues mentioning that you ran into these rough edges and that it made your life a little worse, or with a workaround that you found.

Alternatively, you can continue to write about how much free software sucks.

[0]: https://github.com/rust-lang/rustfmt/issues/3347

[1]: https://github.com/rust-lang/cargo/pull/10344

[2]: https://github.com/rust-lang/cargo/commit/3842d8e6f20067f716...

The new style still supports single line let-else, and there is a configuration parameter to make it be on one line also for longer lines.

It seems there is an issue about this dating all the way back from 2018 but yet it still hasn't been fixed.

However since 4179 recent versions should merge configuration files. Not sure what the details / specifics are but if just ignoring the file entirely is not good enough you might give it its own directory and rustfmt.toml file and see if that works.

Could this be be #3863 - Gives up on chains if any line is too long? It might not be, because I can't see a specific "line" that's too long to format, but there's more detail about the exact problem in the issue.

Rustfmt is a tool that formats Rust code in compliance with style guidelines. Its name precisely reflects its purpose. To install rustfmt, you can run rustup component add rustfmt. Once installed, you can execute cargo fmt to format Rust code in your workspace. If you require further information, you can visit rustfmt’s GitHub repository.

code must be formatted with rustfmt.

Yes, some cases are not yet supported (https://github.com/rust-lang/rustfmt/issues/4914).

Just FYI, the let-else suggestions will only work until rustfmt settles on a format for it. So you may be surprised when this happens and it suddenly changes.