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Make panic message less confusing

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The panic message when slicing a string with a negative length range (eg
`"abcdef"[4..3]`) is confusing: it gives the condition that failed to hold,
whilst all the other panic messages give the condition that did hold.

Before:
begin <= end (4 <= 3) when slicing `abcdef`

After:
begin > end (4 > 3) when slicing `abcdef`
This commit is contained in:
Karl Meakin 2026-02-02 20:56:46 +00:00
parent 262cd76333
commit 94ff542ff5
2 changed files with 3 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

4
library/alloctests/tests/str.rs
View file

@ -612,14 +612,14 @@ mod slice_index {
data: "abcdef";
good: data[4..4] == "";
bad: data[4..3];
message: "begin <= end (4 <= 3)";
message: "begin > end (4 > 3)";
}
in mod rangeinclusive_neg_width {
data: "abcdef";
good: data[4..=3] == "";
bad: data[4..=2];
message: "begin <= end (4 <= 3)";
message: "begin > end (4 > 3)";
}
}

2
library/core/src/str/mod.rs
View file

@ -99,7 +99,7 @@ fn slice_error_fail_rt(s: &str, begin: usize, end: usize) -> ! {
// 3. range is backwards.
if begin > end {
panic!("begin <= end ({begin} <= {end}) when slicing `{s_trunc}`{ellipsis}")
panic!("begin > end ({begin} > {end}) when slicing `{s_trunc}`{ellipsis}")
}
// 4. begin is inside a character.