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mark most of std::str methods as #[must_use] #50479

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mark most of std::str methods as #[must_use] #50479

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16 changes: 16 additions & 0 deletions src/liballoc/str.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,7 @@ pub use core::str::EncodeUtf16;
impl<S: Borrow<str>> SliceConcatExt<str> for [S] {
type Output = String;

#[must_use]
fn concat(&self) -> String {
if self.is_empty() {
return String::new();
Expand All @@ -102,6 +103,7 @@ impl<S: Borrow<str>> SliceConcatExt<str> for [S] {
result
}

#[must_use]
fn join(&self, sep: &str) -> String {
if self.is_empty() {
return String::new();
Expand Down Expand Up @@ -130,13 +132,15 @@ impl<S: Borrow<str>> SliceConcatExt<str> for [S] {
result
}

#[must_use]
fn connect(&self, sep: &str) -> String {
self.join(sep)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl Borrow<str> for String {
#[must_use]
#[inline]
fn borrow(&self) -> &str {
&self[..]
Expand All @@ -146,6 +150,8 @@ impl Borrow<str> for String {
#[stable(feature = "rust1", since = "1.0.0")]
impl ToOwned for str {
type Owned = String;

#[must_use]
fn to_owned(&self) -> String {
unsafe { String::from_utf8_unchecked(self.as_bytes().to_owned()) }
}
Expand Down Expand Up @@ -177,6 +183,7 @@ impl str {
/// let boxed_bytes = boxed_str.into_boxed_bytes();
/// assert_eq!(*boxed_bytes, *s.as_bytes());
/// ```
#[must_use]
#[stable(feature = "str_box_extras", since = "1.20.0")]
#[inline]
pub fn into_boxed_bytes(self: Box<str>) -> Box<[u8]> {
Expand Down Expand Up @@ -303,6 +310,7 @@ impl str {
///
/// assert_eq!(new_year, new_year.to_lowercase());
/// ```
#[must_use]
#[stable(feature = "unicode_case_mapping", since = "1.2.0")]
pub fn to_lowercase(&self) -> String {
let mut s = String::with_capacity(self.len());
Expand Down Expand Up @@ -366,6 +374,7 @@ impl str {
///
/// assert_eq!(new_year, new_year.to_uppercase());
/// ```
#[must_use]
#[stable(feature = "unicode_case_mapping", since = "1.2.0")]
pub fn to_uppercase(&self) -> String {
let mut s = String::with_capacity(self.len());
Expand All @@ -376,6 +385,7 @@ impl str {
/// Escapes each char in `s` with [`char::escape_debug`].
///
/// [`char::escape_debug`]: primitive.char.html#method.escape_debug
#[must_use]
#[unstable(feature = "str_escape",
reason = "return type may change to be an iterator",
issue = "27791")]
Expand All @@ -386,6 +396,7 @@ impl str {
/// Escapes each char in `s` with [`char::escape_default`].
///
/// [`char::escape_default`]: primitive.char.html#method.escape_default
#[must_use]
#[unstable(feature = "str_escape",
reason = "return type may change to be an iterator",
issue = "27791")]
Expand All @@ -396,6 +407,7 @@ impl str {
/// Escapes each char in `s` with [`char::escape_unicode`].
///
/// [`char::escape_unicode`]: primitive.char.html#method.escape_unicode
#[must_use]
#[unstable(feature = "str_escape",
reason = "return type may change to be an iterator",
issue = "27791")]
Expand Down Expand Up @@ -436,6 +448,7 @@ impl str {
/// ```
/// assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));
/// ```
#[must_use]
#[stable(feature = "repeat_str", since = "1.16.0")]
pub fn repeat(&self, n: usize) -> String {
unsafe { String::from_utf8_unchecked(self.as_bytes().repeat(n)) }
Expand All @@ -462,6 +475,7 @@ impl str {
///
/// [`make_ascii_uppercase`]: #method.make_ascii_uppercase
/// [`to_uppercase`]: #method.to_uppercase
#[must_use]
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[inline]
pub fn to_ascii_uppercase(&self) -> String {
Expand Down Expand Up @@ -492,6 +506,7 @@ impl str {
///
/// [`make_ascii_lowercase`]: #method.make_ascii_lowercase
/// [`to_lowercase`]: #method.to_lowercase
#[must_use]
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[inline]
pub fn to_ascii_lowercase(&self) -> String {
Expand All @@ -515,6 +530,7 @@ impl str {
///
/// assert_eq!("☺", &*smile);
/// ```
#[must_use]
#[stable(feature = "str_box_extras", since = "1.20.0")]
#[inline]
pub unsafe fn from_boxed_utf8_unchecked(v: Box<[u8]>) -> Box<str> {
Expand Down