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Warn when an escaped newline skips multiple lines #87671

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Merged
bors merged 4 commits into from
Aug 12, 2021
Merged

Warn when an escaped newline skips multiple lines #87671

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a03fbfe
Warn when an escaped newline skips multiple lines
jesyspa Jul 31, 2021
2dff700
Update format string tests to explicitly escape multiple newlines
jesyspa Jul 31, 2021
efe069c
Add UI tests for string escape warnings.
jesyspa Aug 11, 2021
07aacf5
Renamed variable str -> tail for clarity
jesyspa Aug 11, 2021
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Warn when an escaped newline skips multiple lines
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@jesyspa
jesyspa committed Aug 11, 2021
commit a03fbfe2ff3e7dd03af42d337b11552e782e2dc4
9 changes: 9 additions & 0 deletions compiler/rustc_lexer/src/unescape.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,13 +60,17 @@ pub enum EscapeError {
/// After a line ending with '\', the next line contains whitespace
/// characters that are not skipped.
UnskippedWhitespaceWarning,

/// After a line ending with '\', multiple lines are skipped.
MultipleSkippedLinesWarning,
}

impl EscapeError {
/// Returns true for actual errors, as opposed to warnings.
pub fn is_fatal(&self) -> bool {
match self {
EscapeError::UnskippedWhitespaceWarning => false,
EscapeError::MultipleSkippedLinesWarning => false,
_ => true,
}
}
Expand Down Expand Up @@ -320,6 +324,11 @@ where
.bytes()
.position(|b| b != b' ' && b != b'\t' && b != b'\n' && b != b'\r')
.unwrap_or(str.len());
if str[1..first_non_space].contains('\n') {
// The +1 accounts for the escaping slash.
let end = start + first_non_space + 1;
callback(start..end, Err(EscapeError::MultipleSkippedLinesWarning));
}
let tail = &str[first_non_space..];
if let Some(c) = tail.chars().nth(0) {
// For error reporting, we would like the span to contain the character that was not
Expand Down
5 changes: 5 additions & 0 deletions compiler/rustc_lexer/src/unescape/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,10 @@ fn test_unescape_str_warn() {
assert_eq!(unescaped, expected);
}

// Check we can handle escaped newlines at the end of a file.
check("\\\n", &[]);
check("\\\n ", &[]);

check(
"\\\n \u{a0} x",
&[
Expand All @@ -115,6 +119,7 @@ fn test_unescape_str_warn() {
(6..7, Ok('x')),
],
);
check("\\\n \n x", &[(0..7, Err(EscapeError::MultipleSkippedLinesWarning)), (7..8, Ok('x'))]);
}

#[test]
Expand Down
5 changes: 5 additions & 0 deletions compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
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Expand Up @@ -280,6 +280,11 @@ pub(crate) fn emit_unescape_error(
format!("non-ASCII whitespace symbol '{}' is not skipped", c.escape_unicode());
handler.struct_span_warn(span, &msg).span_label(char_span, &msg).emit();
}
EscapeError::MultipleSkippedLinesWarning => {
let msg = "multiple lines skipped by escaped newline";
let bottom_msg = "skipping everything up to and including this point";
handler.struct_span_warn(span, msg).span_label(span, bottom_msg).emit();
}
}
}

Expand Down