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use std::fmt;
use crate::{
Buffer, ParseError,
err::{perr, ParseErrorKind::*},
escape::unescape,
parse::{first_byte_or_empty, check_suffix},
};
/// A character literal, e.g. `'g'` or `'🦊'`.
///
/// See [the reference][ref] for more information.
///
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct CharLit<B: Buffer> {
raw: B,
/// Start index of the suffix or `raw.len()` if there is no suffix.
start_suffix: usize,
value: char,
}
impl<B: Buffer> CharLit<B> {
/// Parses the input as a character literal. Returns an error if the input
/// is invalid or represents a different kind of literal.
pub fn parse(input: B) -> Result<Self, ParseError> {
match first_byte_or_empty(&input)? {
b'\'' => {
let (value, start_suffix) = parse_impl(&input)?;
Ok(Self { raw: input, value, start_suffix })
},
_ => Err(perr(0, DoesNotStartWithQuote)),
}
}
/// Returns the character value that this literal represents.
pub fn value(&self) -> char {
self.value
}
/// The optional suffix. Returns `""` if the suffix is empty/does not exist.
pub fn suffix(&self) -> &str {
&(*self.raw)[self.start_suffix..]
}
/// Returns the raw input that was passed to `parse`.
pub fn raw_input(&self) -> &str {
&self.raw
}
/// Returns the raw input that was passed to `parse`, potentially owned.
pub fn into_raw_input(self) -> B {
self.raw
}
}
impl CharLit<&str> {
/// Makes a copy of the underlying buffer and returns the owned version of
/// `Self`.
pub fn to_owned(&self) -> CharLit<String> {
CharLit {
raw: self.raw.to_owned(),
start_suffix: self.start_suffix,
value: self.value,
}
}
}
impl<B: Buffer> fmt::Display for CharLit<B> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.pad(&self.raw)
}
}
/// Precondition: first character in input must be `'`.
#[inline(never)]
pub(crate) fn parse_impl(input: &str) -> Result<(char, usize), ParseError> {
let first = input.chars().nth(1).ok_or(perr(None, UnterminatedCharLiteral))?;
let (c, len) = match first {
'\'' if input.chars().nth(2) == Some('\'') => return Err(perr(1, UnescapedSingleQuote)),
'\'' => return Err(perr(None, EmptyCharLiteral)),
'\n' | '\t' | '\r'
=> return Err(perr(1, UnescapedSpecialWhitespace)),
'\\' => unescape::<char>(&input[1..], 1)?,
other => (other, other.len_utf8()),
};
match input[1 + len..].find('\'') {
Some(0) => {}
Some(_) => return Err(perr(None, OverlongCharLiteral)),
None => return Err(perr(None, UnterminatedCharLiteral)),
}
let start_suffix = 1 + len + 1;
let suffix = &input[start_suffix..];
check_suffix(suffix).map_err(|kind| perr(start_suffix, kind))?;
Ok((c, start_suffix))
}
#[cfg(test)]
mod tests;