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pest to chumsky migration #185

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@gerau gerau commented Dec 18, 2025

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apoelstra commented Dec 18, 2025

cc @canndrew may want to keep an eye on progress here

@gerau gerau mentioned this pull request Dec 26, 2025
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@gerau gerau force-pushed the simc/chumsky-migration branch from 6db55db to 1b1e751 Compare January 12, 2026 13:01
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gerau commented Jan 12, 2026

Right now there is a working parser using the chumsky crate which replicates the behavior of the pest parser in terms of building a correct parse tree -- it should produce the same Simplicity program. This implementation also fixes #79.

Error reporting is currently broken because we need to replace the logic of parse::ParseFromStr to return multiple errors or handle recoverable errors differently, and error recovery is proving to be more overwhelming than I estimated it would be.

The code will be refactored because some parts are only half-finished (such as adding Spanned for certain names) and there are better ways to use parser combinators. However, I want to show this progress before implementing error recovery.

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gerau commented Jan 12, 2026

cc @canndrew

uncomputable
uncomputable reviewed Jan 12, 2026
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src/lib.rs
}

#[test]
#[ignore]
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1b1e751 It's nice to see that chumsky seems to be faster than pest here.

gerau added 3 commits January 14, 2026 16:32
@gerau
add lexer
a0473c3 
The lexer parses incoming code into tokens, which makes it simpler to
process using `chumsky`.
@gerau
add parsing for AST using chumsky
c316c67 
This adds parsing via `chumsky` and some necessary changes for it to
work:

- Change `error::Span` type to use byte offset for position. Also add
the `line-index` crate to replace the `line_col` method which was
previously used with the `pest` parser.
- Replace the `PestParse` trait with the `ChumskyParse` trait and the
`ParseFromStr` implementation for it.
@gerau
remove ignore above fuzz_slow_unit_1
1e7c61b 
it's not slow anymore
@gerau gerau force-pushed the simc/chumsky-migration branch from 1b1e751 to 1e7c61b Compare January 14, 2026 15:10
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