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octal_escapes: emit only one lint for all cases found each literal
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@birkenfeld
birkenfeld committed Nov 22, 2021
1 parent 850e7f5 commit 0bc25d0
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Showing 2 changed files with 55 additions and 60 deletions.
69 changes: 48 additions & 21 deletions clippy_lints/src/octal_escapes.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,16 +6,22 @@ use rustc_lint::{EarlyContext, EarlyLintPass};
use rustc_middle::lint::in_external_macro;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::Span;
use std::fmt::Write;

declare_clippy_lint! {
/// ### What it does
/// Checks for `\0` escapes in string and byte literals that look like octal
/// character escapes in C.
///
/// ### Why is this bad?
/// Rust does not support octal notation for character escapes. `\0` is always a
/// null byte/character, and any following digits do not form part of the escape
/// sequence.
///
/// C and other languages support octal character escapes in strings, where
/// a backslash is followed by up to three octal digits. For example, `\033`
/// stands for the ASCII character 27 (ESC). Rust does not support this
/// notation, but has the escape code `\0` which stands for a null
/// byte/character, and any following digits do not form part of the escape
/// sequence. Therefore, `\033` is not a compiler error but the result may
/// be surprising.
///
/// ### Known problems
/// The actual meaning can be the intended one. `\x00` can be used in these
Expand Down Expand Up @@ -58,8 +64,9 @@ impl EarlyLintPass for OctalEscapes {
fn check_lit(cx: &EarlyContext<'tcx>, lit: &Lit, span: Span, is_string: bool) {
let contents = lit.symbol.as_str();
let mut iter = contents.char_indices().peekable();
let mut found = vec![];

// go through the string, looking for \0[0-7]
// go through the string, looking for \0[0-7][0-7]?
while let Some((from, ch)) = iter.next() {
if ch == '\\' {
if let Some((_, '0')) = iter.next() {
Expand All @@ -68,19 +75,41 @@ fn check_lit(cx: &EarlyContext<'tcx>, lit: &Lit, span: Span, is_string: bool) {
if let Some((_, '0'..='7')) = iter.peek() {
to += 1;
}
emit(cx, &contents, from, to + 1, span, is_string);
found.push((from, to + 1));
}
}
}
}
}

fn emit(cx: &EarlyContext<'tcx>, contents: &str, from: usize, to: usize, span: Span, is_string: bool) {
// construct a replacement escape for that case that octal was intended
let escape = &contents[from + 1..to];
// the maximum value is \077, or \x3f
let literal_suggestion = u8::from_str_radix(escape, 8).ok().map(|n| format!("\\x{:02x}", n));
let prefix = if is_string { "" } else { "b" };
if found.is_empty() {
return;
}

// construct two suggestion strings, one with \x escapes with octal meaning
// as in C, and one with \x00 for null bytes.
let mut suggest_1 = if is_string { "\"" } else { "b\"" }.to_string();
let mut suggest_2 = suggest_1.clone();
let mut index = 0;
for (from, to) in found {
suggest_1.push_str(&contents[index..from]);
suggest_2.push_str(&contents[index..from]);

// construct a replacement escape
// the maximum value is \077, or \x3f, so u8 is sufficient here
if let Ok(n) = u8::from_str_radix(&contents[from + 1..to], 8) {
write!(&mut suggest_1, "\\x{:02x}", n).unwrap();
}

// append the null byte as \x00 and the following digits literally
suggest_2.push_str("\\x00");
suggest_2.push_str(&contents[from + 2..to]);

index = to;
}
suggest_1.push_str(&contents[index..]);
suggest_1.push('"');
suggest_2.push_str(&contents[index..]);
suggest_2.push('"');

span_lint_and_then(
cx,
Expand All @@ -96,22 +125,20 @@ fn emit(cx: &EarlyContext<'tcx>, contents: &str, from: usize, to: usize, span: S
if is_string { "character" } else { "byte" }
));
// suggestion 1: equivalent hex escape
if let Some(sugg) = literal_suggestion {
diag.span_suggestion(
span,
"if an octal escape was intended, use the hexadecimal representation instead",
format!("{}\"{}{}{}\"", prefix, &contents[..from], sugg, &contents[to..]),
Applicability::MaybeIncorrect,
);
}
diag.span_suggestion(
span,
"if an octal escape was intended, use the hexadecimal representation instead",
suggest_1,
Applicability::MaybeIncorrect,
);
// suggestion 2: unambiguous null byte
diag.span_suggestion(
span,
&format!(
"if the null {} is intended, disambiguate using",
if is_string { "character" } else { "byte" }
),
format!("{}\"{}\\x00{}\"", prefix, &contents[..from], &contents[from + 2..]),
suggest_2,
Applicability::MaybeIncorrect,
);
},
Expand Down
46 changes: 7 additions & 39 deletions tests/ui/octal_escapes.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -72,28 +72,12 @@ LL | let _bad6 = "Text-/055/077-MoreText";
= help: octal escapes are not supported, `/0` is always a null character
help: if an octal escape was intended, use the hexadecimal representation instead
|
LL | let _bad6 = "Text-/x2d/077-MoreText";
LL | let _bad6 = "Text-/x2d/x3f-MoreText";
| ~~~~~~~~~~~~~~~~~~~~~~~~
help: if the null character is intended, disambiguate using
|
LL | let _bad6 = "Text-/x0055/077-MoreText";
| ~~~~~~~~~~~~~~~~~~~~~~~~~~

error: octal-looking escape in string literal
--> $DIR/octal_escapes.rs:10:17
|
LL | let _bad6 = "Text-/055/077-MoreText";
| ^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: octal escapes are not supported, `/0` is always a null character
help: if an octal escape was intended, use the hexadecimal representation instead
|
LL | let _bad6 = "Text-/055/x3f-MoreText";
| ~~~~~~~~~~~~~~~~~~~~~~~~
help: if the null character is intended, disambiguate using
|
LL | let _bad6 = "Text-/055/x0077-MoreText";
| ~~~~~~~~~~~~~~~~~~~~~~~~~~
LL | let _bad6 = "Text-/x0055/x0077-MoreText";
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: octal-looking escape in string literal
--> $DIR/octal_escapes.rs:11:17
Expand All @@ -104,28 +88,12 @@ LL | let _bad7 = "EvenMoreText-/01/02-ShortEscapes";
= help: octal escapes are not supported, `/0` is always a null character
help: if an octal escape was intended, use the hexadecimal representation instead
|
LL | let _bad7 = "EvenMoreText-/x01/02-ShortEscapes";
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
help: if the null character is intended, disambiguate using
|
LL | let _bad7 = "EvenMoreText-/x001/02-ShortEscapes";
LL | let _bad7 = "EvenMoreText-/x01/x02-ShortEscapes";
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: octal-looking escape in string literal
--> $DIR/octal_escapes.rs:11:17
|
LL | let _bad7 = "EvenMoreText-/01/02-ShortEscapes";
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: octal escapes are not supported, `/0` is always a null character
help: if an octal escape was intended, use the hexadecimal representation instead
|
LL | let _bad7 = "EvenMoreText-/01/x02-ShortEscapes";
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
help: if the null character is intended, disambiguate using
|
LL | let _bad7 = "EvenMoreText-/01/x002-ShortEscapes";
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
LL | let _bad7 = "EvenMoreText-/x001/x002-ShortEscapes";
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: octal-looking escape in string literal
--> $DIR/octal_escapes.rs:12:17
Expand Down Expand Up @@ -159,5 +127,5 @@ help: if the null character is intended, disambiguate using
LL | let _bad9 = "锈/x0011锈";
| ~~~~~~~~~~~~

error: aborting due to 10 previous errors
error: aborting due to 8 previous errors

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