Mercurial > lbo > hg > rcombinators
view src/parser.rs @ 12:a37d7c2aa256
Improve documentation about ParseError
author | Lewin Bormann <lewin@lewin-bormann.info> |
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date | Sun, 02 Jun 2019 15:19:00 +0200 |
parents | 11802adb59ae |
children | d9f4c7963c9f |
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use std::fmt; use crate::combinators; use crate::state::ParseState; #[derive(Debug, PartialEq)] pub enum ParseError { /// Input is over. EOF, /// Input didn't match expectations, try next option if possible. Fail(&'static str, usize), /// Error during application of Transform. TransformFail(&'static str, usize, Box<ParseError>), /// ExecFail is an error that occurred while executing "user code", e.g. during a Transform /// parser. ExecFail(String), } /// This function returns an error for returning from a function called by a `Transform` parser. pub fn execerr<S: AsRef<str>>(s: S) -> ParseError { ParseError::ExecFail(s.as_ref().to_string()) } impl fmt::Display for ParseError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match self { ParseError::EOF => f.write_str("EOF"), ParseError::Fail(s, pos) => write!(f, "Parse fail: {} at {}", s, pos), ParseError::TransformFail(s, pos, inner) => { write!(f, "Transform fail: {} at {} due to ", s, pos).and_then(|()| inner.fmt(f)) } ParseError::ExecFail(s) => { write!(f, "Logic error: {}", s) } } } } pub type ParseResult<R> = Result<R, ParseError>; pub trait Parser { type Result; /// parse consumes input from `st` and returns a result or an error. fn parse( &mut self, st: &mut ParseState<impl Iterator<Item = char>>, ) -> ParseResult<Self::Result>; /// apply transforms the result of this parser using a Transform combinator. fn apply<R2, F: Fn(Self::Result) -> ParseResult<R2>>( self, f: F, ) -> combinators::Transform<Self::Result, R2, Self, F> where Self: std::marker::Sized, { combinators::Transform::new(self, f) } }