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Implement std::error::Error for errors #256

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Implement std::error::Error for errors #256

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33 changes: 33 additions & 0 deletions src/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@

use cow_rc_str::CowRcStr;
use smallvec::SmallVec;
use std::error::Error;
use std::fmt;
use std::ops::BitOr;
use std::ops::Range;
use tokenizer::{SourceLocation, SourcePosition, Token, Tokenizer};
Expand Down Expand Up @@ -53,6 +55,18 @@ pub enum BasicParseErrorKind<'i> {
QualifiedRuleInvalid,
}

impl<'i> BasicParseErrorKind<'i> {
fn description(&self) -> &'static str {
match self {
BasicParseErrorKind::UnexpectedToken(_) => "Unexpected token",
BasicParseErrorKind::EndOfInput => "End of input",
BasicParseErrorKind::AtRuleInvalid(_) => "Invalid @ rule",
BasicParseErrorKind::AtRuleBodyInvalid => "Invalid @ rule body",
BasicParseErrorKind::QualifiedRuleInvalid => "Invalid qualified rule",
}
}
}

/// The funamental parsing errors that can be triggered by built-in parsing routines.
#[derive(Clone, Debug, PartialEq)]
pub struct BasicParseError<'i> {
Expand All @@ -62,6 +76,14 @@ pub struct BasicParseError<'i> {
pub location: SourceLocation,
}

impl<'i> fmt::Display for BasicParseError<'i> {
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
write!(formatter, "{}", self.kind.description())
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This won't print enough information, i.e. we end up not printing the payloads of UnexpectedToken(_) and AtRuleInvalid(_).

}
}

impl<'i> Error for BasicParseError<'i> {}
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Why did you not implement description here?

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The documentation for Error says: "This method is soft-deprecated. Although using it won’t cause compilation warning, new code should use Display instead and new impls can omit it."

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Please implement it anyway, calling BasicParseErrorKind::description.


impl<'i, T> From<BasicParseError<'i>> for ParseError<'i, T> {
#[inline]
fn from(this: BasicParseError<'i>) -> ParseError<'i, T> {
Expand Down Expand Up @@ -156,6 +178,17 @@ impl<'i, T> ParseError<'i, T> {
}
}

impl<'i, T> fmt::Display for ParseError<'i, T> {
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
write!(formatter, "{}", match &self.kind {
ParseErrorKind::Basic(basic_kind) => basic_kind.description(),
ParseErrorKind::Custom(_) => "Custom error",
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Why is the payload disregarded here?

})
Comment on lines +183 to +186
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Please put the match outside and avoid write!.

match &self.kind {
    ParseErrorKind::Basic(basic) => basic.fmt(formatter),
    ParseErrorKind::Custom(_) => "custom error".fmt(formatter),
}

}
}

impl<'i, T> Error for ParseError<'i, T> where T: fmt::Debug {}
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Implement description here.


/// The owned input for a parser.
pub struct ParserInput<'i> {
tokenizer: Tokenizer<'i>,
Expand Down