Visitor in regex_syntax::hir - Rust (original) (raw)

pub trait Visitor {
    type Output;
    type Err;

    // Required method
    fn finish(self) -> Result<Self::Output, Self::Err>;

    // Provided methods
    fn start(&mut self) { ... }
    fn visit_pre(&mut self, _hir: &Hir) -> Result<(), Self::Err> { ... }
    fn visit_post(&mut self, _hir: &Hir) -> Result<(), Self::Err> { ... }
    fn visit_alternation_in(&mut self) -> Result<(), Self::Err> { ... }
    fn visit_concat_in(&mut self) -> Result<(), Self::Err> { ... }
}

Expand description

A trait for visiting the high-level IR (HIR) in depth first order.

The principle aim of this trait is to enable callers to perform case analysis on a high-level intermediate representation of a regular expression without necessarily using recursion. In particular, this permits callers to do case analysis with constant stack usage, which can be important since the size of an HIR may be proportional to end user input.

Typical usage of this trait involves providing an implementation and then running it using the visit function.

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The result of visiting an HIR.

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An error that visiting an HIR might return.

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All implementors of Visitor must provide a finish method, which yields the result of visiting the HIR or an error.

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This method is called before beginning traversal of the HIR.

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This method is called on an Hir before descending into child Hirnodes.

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This method is called on an Hir after descending all of its childHir nodes.

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This method is called between child nodes of an alternation.

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This method is called between child nodes of a concatenation.