Thanks to visit codestin.com
Credit goes to github.com

Skip to content

Use more specific panic message for &str slicing errors #38066

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Jan 4, 2017
Merged

Use more specific panic message for &str slicing errors #38066

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 2 additions & 2 deletions src/doc/book/strings.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -163,8 +163,8 @@ let hachi = &dog[0..2];
with this error:

```text
thread 'main' panicked at 'index 0 and/or 2 in `忠犬ハチ公` do not lie on
character boundary'
thread 'main' panicked at 'byte index 2 is not a char boundary; it is inside '忠'
(bytes 0..3) of `忠犬ハチ公`'
```

## Concatenation
Expand Down
16 changes: 14 additions & 2 deletions src/libcollectionstest/str.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -383,17 +383,29 @@ tempus vel, gravida nec quam.";

// check the panic includes the prefix of the sliced string
#[test]
#[should_panic(expected="Lorem ipsum dolor sit amet")]
#[should_panic(expected="byte index 1024 is out of bounds of `Lorem ipsum dolor sit amet")]
fn test_slice_fail_truncated_1() {
&LOREM_PARAGRAPH[..1024];
}
// check the truncation in the panic message
#[test]
#[should_panic(expected="luctus, im`[...] do not lie on character boundary")]
#[should_panic(expected="luctus, im`[...]")]
fn test_slice_fail_truncated_2() {
&LOREM_PARAGRAPH[..1024];
}

#[test]
#[should_panic(expected="byte index 4 is not a char boundary; it is inside 'α' (bytes 3..5) of")]
fn test_slice_fail_boundary_1() {
&"abcαβγ"[4..];
}

#[test]
#[should_panic(expected="byte index 6 is not a char boundary; it is inside 'β' (bytes 5..7) of")]
fn test_slice_fail_boundary_2() {
&"abcαβγ"[2..6];
}

#[test]
fn test_slice_from() {
assert_eq!(&"abcd"[0..], "abcd");
Expand Down
26 changes: 22 additions & 4 deletions src/libcore/str/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1741,13 +1741,31 @@ fn truncate_to_char_boundary(s: &str, mut max: usize) -> (bool, &str) {
#[cold]
fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! {
const MAX_DISPLAY_LENGTH: usize = 256;
let (truncated, s) = truncate_to_char_boundary(s, MAX_DISPLAY_LENGTH);
let (truncated, s_trunc) = truncate_to_char_boundary(s, MAX_DISPLAY_LENGTH);
let ellipsis = if truncated { "[...]" } else { "" };

// 1. out of bounds
if begin > s.len() || end > s.len() {
let oob_index = if begin > s.len() { begin } else { end };
panic!("byte index {} is out of bounds of `{}`{}", oob_index, s_trunc, ellipsis);
}

// 2. begin <= end
assert!(begin <= end, "begin <= end ({} <= {}) when slicing `{}`{}",
begin, end, s, ellipsis);
panic!("index {} and/or {} in `{}`{} do not lie on character boundary",
begin, end, s, ellipsis);
begin, end, s_trunc, ellipsis);

// 3. character boundary
let index = if !s.is_char_boundary(begin) { begin } else { end };
// find the character
let mut char_start = index;
while !s.is_char_boundary(char_start) {
char_start -= 1;
}
// `char_start` must be less than len and a char boundary
let ch = s[char_start..].chars().next().unwrap();
let char_range = char_start .. char_start + ch.len_utf8();
panic!("byte index {} is not a char boundary; it is inside {:?} (bytes {:?}) of `{}`{}",
index, ch, char_range, s_trunc, ellipsis);
}

#[stable(feature = "core", since = "1.6.0")]
Expand Down