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Rollup merge of #130611 - bjoernager:const-char-encode-utf8, r=dtolnay

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Address diagnostics regression for `const_char_encode_utf8`.

Relevant tracking issue: #130512

This PR regains full diagnostics for non-const calls to `char::encode_utf8`.
This commit is contained in:
Guillaume Gomez 2024-09-20 19:46:38 +02:00 committed by GitHub
commit 2a3f353f04
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1 changed files with 12 additions and 2 deletions
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14
library/core/src/char/methods.rs
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@ -1,6 +1,7 @@
//! impl char {}
use super::*;
use crate::intrinsics::const_eval_select;
use crate::slice;
use crate::str::from_utf8_unchecked_mut;
use crate::unicode::printable::is_printable;
@ -1762,6 +1763,15 @@ const fn len_utf8(code: u32) -> usize {
#[doc(hidden)]
#[inline]
pub const fn encode_utf8_raw(code: u32, dst: &mut [u8]) -> &mut [u8] {
const fn panic_at_const(_code: u32, _len: usize, _dst_len: usize) {
// Note that we cannot format in constant expressions.
panic!("encode_utf8: buffer does not have enough bytes to encode code point");
}
fn panic_at_rt(code: u32, len: usize, dst_len: usize) {
panic!(
"encode_utf8: need {len} bytes to encode U+{code:04X} but buffer has just {dst_len}",
);
}
let len = len_utf8(code);
match (len, &mut *dst) {
(1, [a, ..]) => {
@ -1782,8 +1792,8 @@ pub const fn encode_utf8_raw(code: u32, dst: &mut [u8]) -> &mut [u8] {
*c = (code >> 6 & 0x3F) as u8 | TAG_CONT;
*d = (code & 0x3F) as u8 | TAG_CONT;
}
// Note that we cannot format in constant expressions.
_ => panic!("encode_utf8: buffer does not have enough bytes to encode code point"),
// FIXME(const-hack): We would prefer to have streamlined panics when formatters become const-friendly.
_ => const_eval_select((code, len, dst.len()), panic_at_const, panic_at_rt),
};
// SAFETY: `<&mut [u8]>::as_mut_ptr` is guaranteed to return a valid pointer and `len` has been tested to be within bounds.
unsafe { slice::from_raw_parts_mut(dst.as_mut_ptr(), len) }