bjoernager/rust
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Add #[must_use] to string/char transformation methods

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These methods could be misconstrued as modifying their arguments instead
of returning new values.

Where possible I made the note recommend a method that does mutate in
place.
This commit is contained in:
John Kugelman 2021-10-09 01:01:40 -04:00
parent f8751436ff
commit 54d807cfc7
7 changed files with 40 additions and 0 deletions
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4
library/alloc/src/slice.rs
View file

@ -662,6 +662,8 @@ impl [u8] {
///
/// [`make_ascii_uppercase`]: slice::make_ascii_uppercase
#[cfg(not(no_global_oom_handling))]
#[must_use = "this returns the uppercase bytes as a new Vec, \
without modifying the original"]
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[inline]
pub fn to_ascii_uppercase(&self) -> Vec<u8> {
@ -680,6 +682,8 @@ impl [u8] {
///
/// [`make_ascii_lowercase`]: slice::make_ascii_lowercase
#[cfg(not(no_global_oom_handling))]
#[must_use = "this returns the lowercase bytes as a new Vec, \
without modifying the original"]
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[inline]
pub fn to_ascii_lowercase(&self) -> Vec<u8> {

6
library/alloc/src/str.rs
View file

@ -367,6 +367,8 @@ impl str {
/// assert_eq!(new_year, new_year.to_lowercase());
/// ```
#[cfg(not(no_global_oom_handling))]
#[must_use = "this returns the lowercase string as a new String, \
without modifying the original"]
#[stable(feature = "unicode_case_mapping", since = "1.2.0")]
pub fn to_lowercase(&self) -> String {
let mut s = String::with_capacity(self.len());
@ -447,6 +449,8 @@ impl str {
/// assert_eq!("TSCHÜSS", s.to_uppercase());
/// ```
#[cfg(not(no_global_oom_handling))]
#[must_use = "this returns the uppercase string as a new String, \
without modifying the original"]
#[stable(feature = "unicode_case_mapping", since = "1.2.0")]
pub fn to_uppercase(&self) -> String {
let mut s = String::with_capacity(self.len());
@ -534,6 +538,7 @@ impl str {
/// [`make_ascii_uppercase`]: str::make_ascii_uppercase
/// [`to_uppercase`]: #method.to_uppercase
#[cfg(not(no_global_oom_handling))]
#[must_use = "to uppercase the value in-place, use `make_ascii_lowercase()`"]
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[inline]
pub fn to_ascii_uppercase(&self) -> String {
@ -565,6 +570,7 @@ impl str {
/// [`make_ascii_lowercase`]: str::make_ascii_lowercase
/// [`to_lowercase`]: #method.to_lowercase
#[cfg(not(no_global_oom_handling))]
#[must_use = "to lowercase the value in-place, use `make_ascii_lowercase()`"]
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[inline]
pub fn to_ascii_lowercase(&self) -> String {