1 files changed, 105 insertions, 0 deletions
diff --git a/third_party/rust/litrs/src/char/mod.rs b/third_party/rust/litrs/src/char/mod.rs
new file mode 100644
index 0000000000..54f6f1137f
--- /dev/null
+++ b/third_party/rust/litrs/src/char/mod.rs
@@ -0,0 +1,105 @@
+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.
+///
+/// [ref]: https://doc.rust-lang.org/reference/tokens.html#character-literals
+#[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;