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Unescaping cleanups #103919

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merged 10 commits into from
Nov 9, 2022
Merged

Unescaping cleanups #103919

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f32e678
Rename some variables.
nnethercote Nov 3, 2022
84ca2c3
Clarify range calculations.
nnethercote Nov 3, 2022
34b32b0
Use `Mode` less.
nnethercote Nov 3, 2022
7dbf2c0
Make non-ASCII errors more consistent.
nnethercote Nov 3, 2022
a21c045
Improve comments.
nnethercote Nov 3, 2022
d963686
Refactor `cook_lexer_literal`.
nnethercote Nov 3, 2022
a203482
Inline and remove `validate_int_literal`.
nnethercote Nov 3, 2022
a838952
Remove `unescape_byte_literal`.
nnethercote Nov 4, 2022
43d21b5
Rename some `result` variables as `res`, for consistency.
nnethercote Nov 4, 2022
d6c97a3
Simplify `unescape_{char,byte}`.
nnethercote Nov 8, 2022
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29 changes: 11 additions & 18 deletions compiler/rustc_ast/src/util/literal.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,12 +2,9 @@

use crate::ast::{self, Lit, LitKind};
use crate::token::{self, Token};

use rustc_lexer::unescape::{unescape_byte, unescape_char};
use rustc_lexer::unescape::{unescape_byte_literal, unescape_literal, Mode};
use rustc_lexer::unescape::{byte_from_char, unescape_byte, unescape_char, unescape_literal, Mode};
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_span::Span;

use std::ascii;

pub enum LitError {
Expand Down Expand Up @@ -109,13 +106,11 @@ impl LitKind {
let s = symbol.as_str();
let mut buf = Vec::with_capacity(s.len());
let mut error = Ok(());
unescape_byte_literal(&s, Mode::ByteStr, &mut |_, unescaped_byte| {
match unescaped_byte {
Ok(c) => buf.push(c),
Err(err) => {
if err.is_fatal() {
error = Err(LitError::LexerError);
}
unescape_literal(&s, Mode::ByteStr, &mut |_, c| match c {
Ok(c) => buf.push(byte_from_char(c)),
Err(err) => {
if err.is_fatal() {
error = Err(LitError::LexerError);
}
}
});
Expand All @@ -127,13 +122,11 @@ impl LitKind {
let bytes = if s.contains('\r') {
let mut buf = Vec::with_capacity(s.len());
let mut error = Ok(());
unescape_byte_literal(&s, Mode::RawByteStr, &mut |_, unescaped_byte| {
match unescaped_byte {
Ok(c) => buf.push(c),
Err(err) => {
if err.is_fatal() {
error = Err(LitError::LexerError);
}
unescape_literal(&s, Mode::RawByteStr, &mut |_, c| match c {
Ok(c) => buf.push(byte_from_char(c)),
Err(err) => {
if err.is_fatal() {
error = Err(LitError::LexerError);
}
}
});
Expand Down
10 changes: 5 additions & 5 deletions compiler/rustc_lexer/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -203,13 +203,13 @@ pub enum RawStrError {
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub enum Base {
/// Literal starts with "0b".
Binary,
Binary = 2,
/// Literal starts with "0o".
Octal,
/// Literal starts with "0x".
Hexadecimal,
Octal = 8,
/// Literal doesn't contain a prefix.
Decimal,
Decimal = 10,
/// Literal starts with "0x".
Hexadecimal = 16,
}

/// `rustc` allows files to have a shebang, e.g. "#!/usr/bin/rustrun",
Expand Down
130 changes: 51 additions & 79 deletions compiler/rustc_lexer/src/unescape.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,10 +52,8 @@ pub enum EscapeError {

/// Unicode escape code in byte literal.
UnicodeEscapeInByte,
/// Non-ascii character in byte literal.
/// Non-ascii character in byte literal, byte string literal, or raw byte string literal.
NonAsciiCharInByte,
/// Non-ascii character in byte string literal.
NonAsciiCharInByteString,

/// After a line ending with '\', the next line contains whitespace
/// characters that are not skipped.
Expand All @@ -78,54 +76,33 @@ impl EscapeError {
/// Takes a contents of a literal (without quotes) and produces a
/// sequence of escaped characters or errors.
/// Values are returned through invoking of the provided callback.
pub fn unescape_literal<F>(literal_text: &str, mode: Mode, callback: &mut F)
pub fn unescape_literal<F>(src: &str, mode: Mode, callback: &mut F)
where
F: FnMut(Range<usize>, Result<char, EscapeError>),
{
match mode {
Mode::Char | Mode::Byte => {
let mut chars = literal_text.chars();
let result = unescape_char_or_byte(&mut chars, mode);
// The Chars iterator moved forward.
callback(0..(literal_text.len() - chars.as_str().len()), result);
let mut chars = src.chars();
let res = unescape_char_or_byte(&mut chars, mode == Mode::Byte);
callback(0..(src.len() - chars.as_str().len()), res);
}
Mode::Str | Mode::ByteStr => unescape_str_or_byte_str(literal_text, mode, callback),
// NOTE: Raw strings do not perform any explicit character escaping, here we
// only translate CRLF to LF and produce errors on bare CR.
Mode::Str | Mode::ByteStr => unescape_str_or_byte_str(src, mode == Mode::ByteStr, callback),
Mode::RawStr | Mode::RawByteStr => {
unescape_raw_str_or_raw_byte_str(literal_text, mode, callback)
unescape_raw_str_or_raw_byte_str(src, mode == Mode::RawByteStr, callback)
}
}
}

/// Takes a contents of a byte, byte string or raw byte string (without quotes)
/// and produces a sequence of bytes or errors.
/// Values are returned through invoking of the provided callback.
pub fn unescape_byte_literal<F>(literal_text: &str, mode: Mode, callback: &mut F)
where
F: FnMut(Range<usize>, Result<u8, EscapeError>),
{
debug_assert!(mode.is_bytes());
unescape_literal(literal_text, mode, &mut |range, result| {
callback(range, result.map(byte_from_char));
})
}

/// Takes a contents of a char literal (without quotes), and returns an
/// unescaped char or an error
pub fn unescape_char(literal_text: &str) -> Result<char, (usize, EscapeError)> {
let mut chars = literal_text.chars();
unescape_char_or_byte(&mut chars, Mode::Char)
.map_err(|err| (literal_text.len() - chars.as_str().len(), err))
/// unescaped char or an error.
pub fn unescape_char(src: &str) -> Result<char, EscapeError> {
unescape_char_or_byte(&mut src.chars(), false)
}

/// Takes a contents of a byte literal (without quotes), and returns an
/// unescaped byte or an error.
pub fn unescape_byte(literal_text: &str) -> Result<u8, (usize, EscapeError)> {
let mut chars = literal_text.chars();
unescape_char_or_byte(&mut chars, Mode::Byte)
.map(byte_from_char)
.map_err(|err| (literal_text.len() - chars.as_str().len(), err))
pub fn unescape_byte(src: &str) -> Result<u8, EscapeError> {
unescape_char_or_byte(&mut src.chars(), true).map(byte_from_char)
}

/// What kind of literal do we parse.
Expand All @@ -147,20 +124,17 @@ impl Mode {
}
}

pub fn is_bytes(self) -> bool {
pub fn is_byte(self) -> bool {
match self {
Mode::Byte | Mode::ByteStr | Mode::RawByteStr => true,
Mode::Char | Mode::Str | Mode::RawStr => false,
}
}
}

fn scan_escape(chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {
fn scan_escape(chars: &mut Chars<'_>, is_byte: bool) -> Result<char, EscapeError> {
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// Previous character was '\\', unescape what follows.

let second_char = chars.next().ok_or(EscapeError::LoneSlash)?;

let res = match second_char {
let res = match chars.next().ok_or(EscapeError::LoneSlash)? {
'"' => '"',
'n' => '\n',
'r' => '\r',
Expand All @@ -181,7 +155,7 @@ fn scan_escape(chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {
let value = hi * 16 + lo;

// For a non-byte literal verify that it is within ASCII range.
if !mode.is_bytes() && !is_ascii(value) {
if !is_byte && !is_ascii(value) {
return Err(EscapeError::OutOfRangeHexEscape);
}
let value = value as u8;
Expand Down Expand Up @@ -217,7 +191,7 @@ fn scan_escape(chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {

// Incorrect syntax has higher priority for error reporting
// than unallowed value for a literal.
if mode.is_bytes() {
if is_byte {
return Err(EscapeError::UnicodeEscapeInByte);
}

Expand Down Expand Up @@ -249,23 +223,22 @@ fn scan_escape(chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {
}

#[inline]
fn ascii_check(first_char: char, mode: Mode) -> Result<char, EscapeError> {
if mode.is_bytes() && !first_char.is_ascii() {
fn ascii_check(c: char, is_byte: bool) -> Result<char, EscapeError> {
if is_byte && !c.is_ascii() {
// Byte literal can't be a non-ascii character.
Err(EscapeError::NonAsciiCharInByte)
} else {
Ok(first_char)
Ok(c)
}
}

fn unescape_char_or_byte(chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {
debug_assert!(mode == Mode::Char || mode == Mode::Byte);
let first_char = chars.next().ok_or(EscapeError::ZeroChars)?;
let res = match first_char {
'\\' => scan_escape(chars, mode),
fn unescape_char_or_byte(chars: &mut Chars<'_>, is_byte: bool) -> Result<char, EscapeError> {
let c = chars.next().ok_or(EscapeError::ZeroChars)?;
let res = match c {
'\\' => scan_escape(chars, is_byte),
'\n' | '\t' | '\'' => Err(EscapeError::EscapeOnlyChar),
'\r' => Err(EscapeError::BareCarriageReturn),
_ => ascii_check(first_char, mode),
_ => ascii_check(c, is_byte),
}?;
if chars.next().is_some() {
return Err(EscapeError::MoreThanOneChar);
Expand All @@ -275,20 +248,20 @@ fn unescape_char_or_byte(chars: &mut Chars<'_>, mode: Mode) -> Result<char, Esca

/// Takes a contents of a string literal (without quotes) and produces a
/// sequence of escaped characters or errors.
fn unescape_str_or_byte_str<F>(src: &str, mode: Mode, callback: &mut F)
fn unescape_str_or_byte_str<F>(src: &str, is_byte: bool, callback: &mut F)
where
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(first_char) = chars.next() {
let start = initial_len - chars.as_str().len() - first_char.len_utf8();

let unescaped_char = match first_char {
// 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 res = match c {
'\\' => {
let second_char = chars.clone().next();
match second_char {
match chars.clone().next() {
Some('\n') => {
// Rust language specification requires us to skip whitespaces
// if unescaped '\' character is followed by '\n'.
Expand All @@ -297,17 +270,17 @@ where
skip_ascii_whitespace(&mut chars, start, callback);
continue;
}
_ => scan_escape(&mut chars, mode),
_ => scan_escape(&mut chars, is_byte),
}
}
'\n' => Ok('\n'),
'\t' => Ok('\t'),
'"' => Err(EscapeError::EscapeOnlyChar),
'\r' => Err(EscapeError::BareCarriageReturn),
_ => ascii_check(first_char, mode),
_ => ascii_check(c, is_byte),
};
let end = initial_len - chars.as_str().len();
callback(start..end, unescaped_char);
let end = src.len() - chars.as_str().len();
callback(start..end, res);
}

fn skip_ascii_whitespace<F>(chars: &mut Chars<'_>, start: usize, callback: &mut F)
Expand Down Expand Up @@ -340,30 +313,29 @@ where
/// Takes a contents of a string literal (without quotes) and produces a
/// sequence of characters or errors.
/// NOTE: Raw strings do not perform any explicit character escaping, here we
/// only translate CRLF to LF and produce errors on bare CR.
fn unescape_raw_str_or_raw_byte_str<F>(literal_text: &str, mode: Mode, callback: &mut F)
/// only produce errors on bare CR.
fn unescape_raw_str_or_raw_byte_str<F>(src: &str, is_byte: bool, callback: &mut F)
where
F: FnMut(Range<usize>, Result<char, EscapeError>),
{
debug_assert!(mode == Mode::RawStr || mode == Mode::RawByteStr);
let initial_len = literal_text.len();

let mut chars = literal_text.chars();
while let Some(curr) = chars.next() {
let start = initial_len - chars.as_str().len() - curr.len_utf8();
let mut chars = src.chars();

let result = match curr {
// 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 res = match c {
'\r' => Err(EscapeError::BareCarriageReturnInRawString),
c if mode.is_bytes() && !c.is_ascii() => Err(EscapeError::NonAsciiCharInByteString),
c => Ok(c),
_ => ascii_check(c, is_byte),
};
let end = initial_len - chars.as_str().len();

callback(start..end, result);
let end = src.len() - chars.as_str().len();
callback(start..end, res);
}
}

fn byte_from_char(c: char) -> u8 {
#[inline]
pub fn byte_from_char(c: char) -> u8 {
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This one is a bit dicey. I agree that in the context of compiler we don't really care about nice abstrction boundaries, and this is a simplification.

But we want rustc_lexer to also be a nice crates.io crates, and from that point of view this feels a bit too type-unsafe.

No strong opinion overall.

Though, if we do this, this one surely wants to be tagged as #[inline]? tiny cross-crate fn.

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It's a fair point. A couple of questions:

  • Is rustc_lexer actually usable outside of rustc/rust-analyzer? the rustc-lexer crate is v0.1.0 and hasn't been updated in three years. I see some auto-updated variants but none of them have been updated in the past year.
  • I'm not sure how this is type-unsafe. You'll get u8/char type mismatches if you do something wrong?
  • Inlining is a good idea.

let res = c as u32;
debug_assert!(res <= u8::MAX as u32, "guaranteed because of Mode::ByteStr");
res as u8
Expand Down
29 changes: 10 additions & 19 deletions compiler/rustc_lexer/src/unescape/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,7 @@ use super::*;
#[test]
fn test_unescape_char_bad() {
fn check(literal_text: &str, expected_error: EscapeError) {
let actual_result = unescape_char(literal_text).map_err(|(_offset, err)| err);
assert_eq!(actual_result, Err(expected_error));
assert_eq!(unescape_char(literal_text), Err(expected_error));
}

check("", EscapeError::ZeroChars);
Expand Down Expand Up @@ -68,8 +67,7 @@ fn test_unescape_char_bad() {
#[test]
fn test_unescape_char_good() {
fn check(literal_text: &str, expected_char: char) {
let actual_result = unescape_char(literal_text);
assert_eq!(actual_result, Ok(expected_char));
assert_eq!(unescape_char(literal_text), Ok(expected_char));
}

check("a", 'a');
Expand Down Expand Up @@ -149,8 +147,7 @@ fn test_unescape_str_good() {
#[test]
fn test_unescape_byte_bad() {
fn check(literal_text: &str, expected_error: EscapeError) {
let actual_result = unescape_byte(literal_text).map_err(|(_offset, err)| err);
assert_eq!(actual_result, Err(expected_error));
assert_eq!(unescape_byte(literal_text), Err(expected_error));
}

check("", EscapeError::ZeroChars);
Expand Down Expand Up @@ -219,8 +216,7 @@ fn test_unescape_byte_bad() {
#[test]
fn test_unescape_byte_good() {
fn check(literal_text: &str, expected_byte: u8) {
let actual_result = unescape_byte(literal_text);
assert_eq!(actual_result, Ok(expected_byte));
assert_eq!(unescape_byte(literal_text), Ok(expected_byte));
}

check("a", b'a');
Expand All @@ -246,10 +242,10 @@ fn test_unescape_byte_good() {
fn test_unescape_byte_str_good() {
fn check(literal_text: &str, expected: &[u8]) {
let mut buf = Ok(Vec::with_capacity(literal_text.len()));
unescape_byte_literal(literal_text, Mode::ByteStr, &mut |range, c| {
unescape_literal(literal_text, Mode::ByteStr, &mut |range, c| {
if let Ok(b) = &mut buf {
match c {
Ok(c) => b.push(c),
Ok(c) => b.push(byte_from_char(c)),
Err(e) => buf = Err((range, e)),
}
}
Expand Down Expand Up @@ -280,18 +276,13 @@ fn test_unescape_raw_str() {

#[test]
fn test_unescape_raw_byte_str() {
fn check(literal: &str, expected: &[(Range<usize>, Result<u8, EscapeError>)]) {
fn check(literal: &str, expected: &[(Range<usize>, Result<char, EscapeError>)]) {
let mut unescaped = Vec::with_capacity(literal.len());
unescape_byte_literal(literal, Mode::RawByteStr, &mut |range, res| {
unescaped.push((range, res))
});
unescape_literal(literal, Mode::RawByteStr, &mut |range, res| unescaped.push((range, res)));
assert_eq!(unescaped, expected);
}

check("\r", &[(0..1, Err(EscapeError::BareCarriageReturnInRawString))]);
check("🦀", &[(0..4, Err(EscapeError::NonAsciiCharInByteString))]);
check(
"🦀a",
&[(0..4, Err(EscapeError::NonAsciiCharInByteString)), (4..5, Ok(byte_from_char('a')))],
);
check("🦀", &[(0..4, Err(EscapeError::NonAsciiCharInByte))]);
check("🦀a", &[(0..4, Err(EscapeError::NonAsciiCharInByte)), (4..5, Ok('a'))]);
}
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