litrs/char/
mod.rs

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1use std::fmt;
2
3use crate::{
4    Buffer, ParseError,
5    err::{perr, ParseErrorKind::*},
6    escape::unescape,
7    parse::first_byte_or_empty,
8};
9
10
11/// A character literal, e.g. `'g'` or `'🦊'`.
12///
13/// See [the reference][ref] for more information.
14///
15/// [ref]: https://doc.rust-lang.org/reference/tokens.html#character-literals
16#[derive(Debug, Clone, Copy, PartialEq, Eq)]
17pub struct CharLit<B: Buffer> {
18    raw: B,
19    value: char,
20}
21
22impl<B: Buffer> CharLit<B> {
23    /// Parses the input as a character literal. Returns an error if the input
24    /// is invalid or represents a different kind of literal.
25    pub fn parse(input: B) -> Result<Self, ParseError> {
26        match first_byte_or_empty(&input)? {
27            b'\'' => Self::parse_impl(input),
28            _ => Err(perr(0, DoesNotStartWithQuote)),
29        }
30    }
31
32    /// Returns the character value that this literal represents.
33    pub fn value(&self) -> char {
34        self.value
35    }
36
37    /// Precondition: first character in input must be `'`.
38    pub(crate) fn parse_impl(input: B) -> Result<Self, ParseError> {
39        if input.len() == 1 {
40            return Err(perr(None, UnterminatedCharLiteral));
41        }
42        if *input.as_bytes().last().unwrap() != b'\'' {
43            return Err(perr(None, UnterminatedCharLiteral));
44        }
45
46        let inner = &input[1..input.len() - 1];
47        let first = inner.chars().nth(0).ok_or(perr(None, EmptyCharLiteral))?;
48        let (c, len) = match first {
49            '\'' => return Err(perr(1, UnescapedSingleQuote)),
50            '\n' | '\t' | '\r'
51                => return Err(perr(1, UnescapedSpecialWhitespace)),
52
53            '\\' => unescape::<char>(inner, 1)?,
54            other => (other, other.len_utf8()),
55        };
56        let rest = &inner[len..];
57
58        if !rest.is_empty() {
59            return Err(perr(len + 1..input.len() - 1, OverlongCharLiteral));
60        }
61
62        Ok(Self {
63            raw: input,
64            value: c,
65        })
66    }
67}
68
69impl CharLit<&str> {
70    /// Makes a copy of the underlying buffer and returns the owned version of
71    /// `Self`.
72    pub fn to_owned(&self) -> CharLit<String> {
73        CharLit {
74            raw: self.raw.to_owned(),
75            value: self.value,
76        }
77    }
78}
79
80impl<B: Buffer> fmt::Display for CharLit<B> {
81    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
82        f.pad(&self.raw)
83    }
84}
85
86
87#[cfg(test)]
88mod tests;
litrs/char/mod.rs

litrs/char/
mod.rs
