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Auto merge of #97367 - WaffleLapkin:stabilize_checked_slice_to_str_conv, r=dtolnay

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Stabilize checked slice->str conversion functions

This PR stabilizes the following APIs as `const` functions in Rust 1.63:
```rust
// core::str

pub const fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error>;

impl Utf8Error {
    pub const fn valid_up_to(&self) -> usize;
    pub const fn error_len(&self) -> Option<usize>;
}
```

Note that the `from_utf8_mut` function is not stabilized as unique references (`&mut _`) are [unstable in const context].

FCP: https://github.com/rust-lang/rust/issues/91006#issuecomment-1134593095

[unstable in const context]: https://github.com/rust-lang/rust/issues/57349
This commit is contained in:
bors 2022-06-19 05:51:42 +00:00
commit 5fb8a39266
2 changed files with 6 additions and 5 deletions
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5
library/core/src/str/converts.rs
View File

@ -82,9 +82,10 @@ use super::Utf8Error;
/// assert_eq!("💖", sparkle_heart);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_unstable(feature = "const_str_from_utf8", issue = "91006")]
#[rustc_const_stable(feature = "const_str_from_utf8_shared", since = "1.63.0")]
#[rustc_allow_const_fn_unstable(str_internals)]
pub const fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
// This should use `?` again, once it's `const`
// FIXME: This should use `?` again, once it's `const`
match run_utf8_validation(v) {
Ok(_) => {
// SAFETY: validation succeeded.

6
library/core/src/str/error.rs
View File

@ -72,7 +72,7 @@ impl Utf8Error {
/// assert_eq!(1, error.valid_up_to());
/// ```
#[stable(feature = "utf8_error", since = "1.5.0")]
#[rustc_const_unstable(feature = "const_str_from_utf8", issue = "91006")]
#[rustc_const_stable(feature = "const_str_from_utf8_shared", since = "1.63.0")]
#[must_use]
#[inline]
pub const fn valid_up_to(&self) -> usize {
@ -95,11 +95,11 @@ impl Utf8Error {
///
/// [U+FFFD]: ../../std/char/constant.REPLACEMENT_CHARACTER.html
#[stable(feature = "utf8_error_error_len", since = "1.20.0")]
#[rustc_const_unstable(feature = "const_str_from_utf8", issue = "91006")]
#[rustc_const_stable(feature = "const_str_from_utf8_shared", since = "1.63.0")]
#[must_use]
#[inline]
pub const fn error_len(&self) -> Option<usize> {
// This should become `map` again, once it's `const`
// FIXME: This should become `map` again, once it's `const`
match self.error_len {
Some(len) => Some(len as usize),
None => None,