Auto merge of #126965 - matthiaskrgr:rollup-x3kamn8, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #126302 (Detect unused structs which derived Default)
 - #126885 (Remove internal `PathBuf::as_mut_vec`)
 - #126916 (Specify target specific linker for `riscv64gc-gnu` job)
 - #126926 (Tweak a confusing comment in `create_match_candidates`)
 - #126927 (core: VaArgSafe is an unsafe trait)
 - #126932 (Tweak `FlatPat::new` to avoid a temporarily-invalid state)
 - #126946 (Add missing slash in `const_eval_select` doc comment)
 - #126947 (Delegation: ast lowering refactor)

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 6 insertions, 6 deletions

diff --git a/library/std/src/sys_common/wtf8.rs b/library/std/src/sys_common/wtf8.rs
index 84128a4b595..708f62f476e 100644
--- a/library/std/src/sys_common/wtf8.rs
+++ b/library/std/src/sys_common/wtf8.rs
@@ -474,13 +474,13 @@ impl Wtf8Buf {
         Wtf8Buf { bytes: bytes.into_vec(), is_known_utf8: false }
     }
 
-    /// Part of a hack to make PathBuf::push/pop more efficient.
+    /// Provides plumbing to core `Vec::extend_from_slice`.
+    /// More well behaving alternative to allowing outer types
+    /// full mutable access to the core `Vec`.
     #[inline]
-    pub(crate) fn as_mut_vec_for_path_buf(&mut self) -> &mut Vec<u8> {
-        // FIXME: this function should not even exist, as it implies violating Wtf8Buf invariants
-        // For now, simply assume that is about to happen.
-        self.is_known_utf8 = false;
-        &mut self.bytes
+    pub(crate) fn extend_from_slice(&mut self, other: &[u8]) {
+        self.bytes.extend_from_slice(other);
+        self.is_known_utf8 = self.is_known_utf8 || self.next_surrogate(0).is_none();
     }
 }