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71 changes: 28 additions & 43 deletions src/libsyntax/parse/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -286,52 +286,37 @@ pub fn tts_to_parser<'a>(sess: &'a ParseSess,
pub fn char_lit(lit: &str) -> (char, isize) {
use std::char;

let mut chars = lit.chars();
match (chars.next(), chars.next()) {
(Some(c), None) if c != '\\' => return (c, 1),
(Some('\\'), Some(c)) => match c {
'"' => return ('"', 2),
'n' => return ('\n', 2),
'r' => return ('\r', 2),
't' => return ('\t', 2),
'\\' => return ('\\', 2),
'\'' => return ('\'', 2),
'0' => return ('\0', 2),
_ => {}
},
_ => panic!("lexer accepted invalid char escape `{}`", lit)
};

fn esc(len: usize, lit: &str) -> Option<(char, isize)> {
u32::from_str_radix(&lit[2..len], 16).ok()
.and_then(char::from_u32)
.map(|x| (x, len as isize))
// Handle non-escaped chars first.
if lit.as_bytes()[0] != b'\\' {
// If the first byte isn't '\\' it might part of a multi-byte char, so
// get the char with chars().
let c = lit.chars().next().unwrap();
return (c, 1);
}

let unicode_escape = || -> Option<(char, isize)> {
if lit.as_bytes()[2] == b'{' {
let idx = lit.find('}').unwrap_or_else(|| {
panic!("lexer should have rejected a bad character escape {}", lit)
});

let subslice = &lit[3..idx];
u32::from_str_radix(subslice, 16).ok()
.and_then(char::from_u32)
.map(|x| (x, subslice.chars().count() as isize + 4))
} else {
esc(6, lit)
// Handle escaped chars.
match lit.as_bytes()[1] as char {
'"' => ('"', 2),
'n' => ('\n', 2),
'r' => ('\r', 2),
't' => ('\t', 2),
'\\' => ('\\', 2),
'\'' => ('\'', 2),
'0' => ('\0', 2),
'x' => {
let v = u32::from_str_radix(&lit[2..4], 16).unwrap();
let c = char::from_u32(v).unwrap();
(c, 4)
}
};

// Unicode escapes
return match lit.as_bytes()[1] as char {
'x' | 'X' => esc(4, lit),
'u' => unicode_escape(),
'U' => esc(10, lit),
_ => None,
}.unwrap_or_else(|| {
panic!("lexer should have rejected a bad character escape {}", lit)
})
'u' => {
assert!(lit.as_bytes()[2] == b'{');
let idx = lit.find('}').unwrap();
let v = u32::from_str_radix(&lit[3..idx], 16).unwrap();
let c = char::from_u32(v).unwrap();
(c, (idx + 1) as isize)
}
_ => panic!("lexer should have rejected a bad character escape {}", lit)
}
}

/// Parse a string representing a string literal into its final form. Does
Expand Down