std: Change `encode_utf{8,16}` to return iterators

Currently these have non-traditional APIs which take a buffer and report how
much was filled in, but they're not necessarily ergonomic to use. Returning an
iterator which *also* exposes an underlying slice shouldn't result in any
performance loss as it's just a lazy version of the same implementation, and
it's also much more ergonomic!

cc #27784

1 files changed, 3 insertions, 4 deletions

diff --git a/src/libserialize/json.rs b/src/libserialize/json.rs
index b95eddbc661..ab16ef23dd1 100644
--- a/src/libserialize/json.rs
+++ b/src/libserialize/json.rs
@@ -433,10 +433,9 @@ fn escape_str(wr: &mut fmt::Write, v: &str) -> EncodeResult {
 }
 
 fn escape_char(writer: &mut fmt::Write, v: char) -> EncodeResult {
-    let mut buf = [0; 4];
-    let n = v.encode_utf8(&mut buf).unwrap();
-    let buf = unsafe { str::from_utf8_unchecked(&buf[..n]) };
-    escape_str(writer, buf)
+    escape_str(writer, unsafe {
+        str::from_utf8_unchecked(v.encode_utf8().as_slice())
+    })
 }
 
 fn spaces(wr: &mut fmt::Write, mut n: usize) -> EncodeResult {