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Clarify range calculations.

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There is some subtlety here.
This commit is contained in:
Nicholas Nethercote 2022-11-03 12:15:55 +11:00
parent f32e6781b2
commit 84ca2c3bab
1 changed files with 12 additions and 10 deletions
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22
compiler/rustc_lexer/src/unescape.rs
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@ -275,11 +275,13 @@ fn unescape_str_or_byte_str<F>(src: &str, mode: Mode, callback: &mut F)
F: FnMut(Range<usize>, Result<char, EscapeError>),
{
debug_assert!(mode == Mode::Str || mode == Mode::ByteStr);
let initial_len = src.len();
let mut chars = src.chars();
while let Some(c) = chars.next() {
let start = initial_len - chars.as_str().len() - c.len_utf8();
// The `start` and `end` computation here is complicated because
// `skip_ascii_whitespace` makes us to skip over chars without counting
// them in the range computation.
while let Some(c) = chars.next() {
let start = src.len() - chars.as_str().len() - c.len_utf8();
let result = match c {
'\\' => {
match chars.clone().next() {
@ -300,7 +302,7 @@ fn unescape_str_or_byte_str<F>(src: &str, mode: Mode, callback: &mut F)
'\r' => Err(EscapeError::BareCarriageReturn),
_ => ascii_check(c, mode),
};
let end = initial_len - chars.as_str().len();
let end = src.len() - chars.as_str().len();
callback(start..end, result);
}
@ -340,19 +342,19 @@ fn unescape_raw_str_or_raw_byte_str<F>(src: &str, mode: Mode, callback: &mut F)
F: FnMut(Range<usize>, Result<char, EscapeError>),
{
debug_assert!(mode == Mode::RawStr || mode == Mode::RawByteStr);
let initial_len = src.len();
let mut chars = src.chars();
while let Some(c) = chars.next() {
let start = initial_len - chars.as_str().len() - c.len_utf8();
// The `start` and `end` computation here matches the one in
// `unescape_str_or_byte_str` for consistency, even though this function
// doesn't have to worry about skipping any chars.
while let Some(c) = chars.next() {
let start = src.len() - chars.as_str().len() - c.len_utf8();
let result = match c {
'\r' => Err(EscapeError::BareCarriageReturnInRawString),
c if mode.is_bytes() && !c.is_ascii() => Err(EscapeError::NonAsciiCharInByteString),
c => Ok(c),
};
let end = initial_len - chars.as_str().len();
let end = src.len() - chars.as_str().len();
callback(start..end, result);
}
}