Immutable parser (Tokenize borrow strings cont)#2098
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iffyio merged 1 commit intoapache:reduce-string-copyingfrom Dec 18, 2025
Merged
Immutable parser (Tokenize borrow strings cont)#2098iffyio merged 1 commit intoapache:reduce-string-copyingfrom
iffyio merged 1 commit intoapache:reduce-string-copyingfrom
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Changed all parsing methods to take '&self' instead of '\&mut self'. Mutable parser state (token index and parser state) now uses for interior mutability. This refactoring is preparation for the borrowed tokenizer work. When holding borrowed tokens from the parser (with lifetime tied to '\&self'), we cannot call methods requiring '\&mut self' due to Rust's borrowing rules. Using interior mutability resolves this conflict by allowing state mutations through shared references.
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iffyio
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Dec 18, 2025
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iffyio
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LGTM! Thanks @eyalleshem!
alamb
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Dec 24, 2025
| @@ -331,9 +332,9 @@ pub struct Parser<'a> { | |||
| /// The tokens | |||
| tokens: Vec<TokenWithSpan>, | |||
| /// The index of the first unprocessed token in [`Parser::tokens`]. | |||
| index: usize, | |||
| index: Cell<usize>, | |||
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This is a clever way to go about reducing the need for mutable borrows. Thank you @eyalleshem
One thing that might be worth doing (perhaps as a follow on PR) is documenting how this works (notable that Parser has interior mutability so functions like next_token() actually do change state, even though they are immutable
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refactor: Make Parser methods immutable using interior mutability
Changed all parsing methods to take
&selfinstead of&mut self.Mutable parser state (token index and parser state) now uses
Cellfor interior mutability.
This refactoring is preparation for the borrowed tokenizer work. When
holding borrowed tokens from the parser (with lifetime tied to
&self),we cannot call methods requiring
&mut selfdue to Rust's borrowingrules. Using interior mutability resolves this conflict by allowing
state mutations through shared references.