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Clarify ascii whitespace exclusion of vertical tab in the doc #154765

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Merged
rust-bors merged 2 commits into from
Apr 15, 2026
Merged

Clarify ascii whitespace exclusion of vertical tab in the doc #154765

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5ac90c6
Clarify ascii whitespace exclusion of vertical tab in the doc
krtab Apr 3, 2026
b52a38d
Add link to Unicode White_Space property
krtab Apr 13, 2026
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3 changes: 3 additions & 0 deletions library/core/src/char/methods.rs
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Expand Up @@ -1930,6 +1930,9 @@ impl char {
/// U+0020 SPACE, U+0009 HORIZONTAL TAB, U+000A LINE FEED,
/// U+000C FORM FEED, or U+000D CARRIAGE RETURN.
///
/// **Warning:** Because the list above excludes U+000B VERTICAL TAB,
/// `c.is_ascii_whitespace()` is **not** equivalent to `c.is_ascii() && c.is_whitespace()`.
///
/// Rust uses the WhatWG Infra Standard's [definition of ASCII
/// whitespace][infra-aw]. There are several other definitions in
/// wide use. For instance, [the POSIX locale][pct] includes
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3 changes: 3 additions & 0 deletions library/core/src/num/mod.rs
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Expand Up @@ -1064,6 +1064,9 @@ impl u8 {
/// U+0020 SPACE, U+0009 HORIZONTAL TAB, U+000A LINE FEED,
/// U+000C FORM FEED, or U+000D CARRIAGE RETURN.
///
/// **Warning:** Because the list above excludes U+000B VERTICAL TAB,
/// `b.is_ascii_whitespace()` is **not** equivalent to `char::from(b).is_whitespace()`.
///
/// Rust uses the WhatWG Infra Standard's [definition of ASCII
/// whitespace][infra-aw]. There are several other definitions in
/// wide use. For instance, [the POSIX locale][pct] includes
Expand Down
18 changes: 15 additions & 3 deletions library/core/src/slice/ascii.rs
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Expand Up @@ -222,7 +222,11 @@ impl [u8] {
/// Returns a byte slice with leading ASCII whitespace bytes removed.
///
/// 'Whitespace' refers to the definition used by
/// [`u8::is_ascii_whitespace`].
/// [`u8::is_ascii_whitespace`]. Importantly, this definition excludes
/// the `\0x0B` byte even though it has the Unicode [`White_Space`] property
/// and is removed by [`str::trim_start`].
///
/// [`White_Space`]: https://www.unicode.org/reports/tr44/#White_Space
///
/// # Examples
///
Expand Down Expand Up @@ -251,7 +255,11 @@ impl [u8] {
/// Returns a byte slice with trailing ASCII whitespace bytes removed.
///
/// 'Whitespace' refers to the definition used by
/// [`u8::is_ascii_whitespace`].
/// [`u8::is_ascii_whitespace`]. Importantly, this definition excludes
/// the `\0x0B` byte even though it has the Unicode [`White_Space`] property
/// and is removed by [`str::trim_end`].
Comment on lines +258 to +260
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@Jules-Bertholet Jules-Bertholet Apr 8, 2026 •
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View changes since the review

Suggested change
/// [`u8::is_ascii_whitespace`]. Importantly, this definition excludes
/// the `\0x0B` byte even though it has the unicode WhiteSpace property
/// and is removed by [`str::trim_end`].
/// [`u8::is_ascii_whitespace`]. Importantly, this definition excludes
/// the `\0x0B` byte even though it has the Unicode [`White_Space`] property
/// and is removed by [`str::trim_end`].
///
/// [`White_Space`]: https://www.unicode.org/reports/tr44/#White_Space

… and so on for other references to the property.

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@asquared31415 asquared31415 Apr 11, 2026

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Maybe "Importantly, unlike is_whitespace, this definition..." to draw attention to the contrast between them?

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@krtab krtab Apr 13, 2026

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@asquared31415 I like your idea but I feel like this is already implied by highlighting the difference with the various trim_* and I don't want to make the doc too long so I have elected to not do incoporate your suggestion for now.

///
/// [`White_Space`]: https://www.unicode.org/reports/tr44/#White_Space
///
/// # Examples
///
Expand Down Expand Up @@ -281,7 +289,11 @@ impl [u8] {
/// removed.
///
/// 'Whitespace' refers to the definition used by
/// [`u8::is_ascii_whitespace`].
/// [`u8::is_ascii_whitespace`]. Importantly, this definition excludes
/// the `\0x0B` byte even though it has the Unicode [`White_Space`] property
/// and is removed by [`str::trim`].
///
/// [`White_Space`]: https://www.unicode.org/reports/tr44/#White_Space
///
/// # Examples
///
Expand Down
18 changes: 15 additions & 3 deletions library/core/src/str/mod.rs
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Expand Up @@ -1202,6 +1202,9 @@ impl str {
///
/// This uses the same definition as [`char::is_ascii_whitespace`].
/// To split by Unicode `Whitespace` instead, use [`split_whitespace`].
/// Note that because of this difference in definition, even if `s.is_ascii()`
/// is `true`, `s.split_ascii_whitespace()` behavior will differ from `s.split_whitespace()`
/// if `s` contains U+000B VERTICAL TAB.
///
/// [`split_whitespace`]: str::split_whitespace
///
Expand Down Expand Up @@ -2896,9 +2899,12 @@ impl str {
/// Returns a string slice with leading ASCII whitespace removed.
///
/// 'Whitespace' refers to the definition used by
/// [`u8::is_ascii_whitespace`].
/// [`u8::is_ascii_whitespace`]. Importantly, this definition excludes
/// the U+000B code point even though it has the Unicode [`White_Space`] property
/// and is removed by [`str::trim_start`].
///
/// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
/// [`White_Space`]: https://www.unicode.org/reports/tr44/#White_Space
///
/// # Examples
///
Expand All @@ -2921,9 +2927,12 @@ impl str {
/// Returns a string slice with trailing ASCII whitespace removed.
///
/// 'Whitespace' refers to the definition used by
/// [`u8::is_ascii_whitespace`].
/// [`u8::is_ascii_whitespace`]. Importantly, this definition excludes
/// the U+000B code point even though it has the Unicode [`White_Space`] property
/// and is removed by [`str::trim_end`].
///
/// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
/// [`White_Space`]: https://www.unicode.org/reports/tr44/#White_Space
///
/// # Examples
///
Expand All @@ -2947,9 +2956,12 @@ impl str {
/// removed.
///
/// 'Whitespace' refers to the definition used by
/// [`u8::is_ascii_whitespace`].
/// [`u8::is_ascii_whitespace`]. Importantly, this definition excludes
/// the U+000B code point even though it has the Unicode [`White_Space`] property
/// and is removed by [`str::trim`].
///
/// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
/// [`White_Space`]: https://www.unicode.org/reports/tr44/#White_Space
///
/// # Examples
///
Expand Down
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