Rollup merge of #72683 - RalfJung:char-debug-check, r=Mark-Simulacrum

from_u32_unchecked: check validity, and fix UB in Wtf8

Fixes https://github.com/rust-lang/rust/issues/72760

2 files changed, 3 insertions, 4 deletions

diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 9ddaa100c0e..d6493454db5 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -247,6 +247,7 @@
 #![feature(cfg_target_has_atomic)]
 #![feature(cfg_target_thread_local)]
 #![feature(char_error_internals)]
+#![feature(char_internals)]
 #![feature(clamp)]
 #![feature(concat_idents)]
 #![feature(const_cstr_unchecked)]
diff --git a/src/libstd/sys_common/wtf8.rs b/src/libstd/sys_common/wtf8.rs
index a5ba3daba3e..bdb6a05464e 100644
--- a/src/libstd/sys_common/wtf8.rs
+++ b/src/libstd/sys_common/wtf8.rs
@@ -201,9 +201,8 @@ impl Wtf8Buf {
     /// Copied from String::push
     /// This does **not** include the WTF-8 concatenation check.
     fn push_code_point_unchecked(&mut self, code_point: CodePoint) {
-        let c = unsafe { char::from_u32_unchecked(code_point.value) };
         let mut bytes = [0; 4];
-        let bytes = c.encode_utf8(&mut bytes).as_bytes();
+        let bytes = char::encode_utf8_raw(code_point.value, &mut bytes);
         self.bytes.extend_from_slice(bytes)
     }
 
@@ -840,8 +839,7 @@ impl<'a> Iterator for EncodeWide<'a> {
 
         let mut buf = [0; 2];
         self.code_points.next().map(|code_point| {
-            let c = unsafe { char::from_u32_unchecked(code_point.value) };
-            let n = c.encode_utf16(&mut buf).len();
+            let n = char::encode_utf16_raw(code_point.value, &mut buf).len();
             if n == 2 {
                 self.extra = buf[1];
             }