FIX: Remove use of uninitialized in ArrayString

We can't fix this properly (MaybeUninit with a union) until we change
the user visible API (we need to require that A: Copy.

As a temporary solution for arrayvec version 0.4.*, we use zeroed to
initialize an array of bytes, instead of using uninitialized. This may
have a negative performance impact, but the fix is to upgrade to future
arrayvec 0.5.

src/array_string.rs

@@ -26,6 +26,7 @@ use serde::{Serialize, Deserialize, Serializer, Deserializer};
 /// if needed.
 #[derive(Copy)]
 pub struct ArrayString<A: Array<Item=u8>> {
+    // FIXME: Use Copyable union for xs when we can
     xs: A,
     len: A::Index,
 }
@@ -53,7 +54,8 @@ impl<A: Array<Item=u8>> ArrayString<A> {
     pub fn new() -> ArrayString<A> {
         unsafe {
             ArrayString {
-                xs: ::new_array(),
+                // FIXME: Use Copyable union for xs when we can
+                xs: mem::zeroed(),
                 len: Index::from(0),
             }
         }