fix: .unwrap() requires Err(E: Debug), a luxuary we cannot afford

Author: Teufelchen1

library/alloc/src/vec/mod.rs

@@ -1761,7 +1761,16 @@ impl<T, A: Allocator> Vec<T, A> {
     #[unstable(feature = "alloc_slice_into_array", issue = "148082")]
     #[must_use]
     pub fn into_array<const N: usize>(self) -> Result<Box<[T; N], A>, Self> {
-        if self.len() == N { Ok(self.into_boxed_slice().into_array().unwrap()) } else { Err(self) }
+        if self.len() == N {
+            unsafe {
+                let me = ManuallyDrop::new(self);
+                let buf = me.buf.ptr() as *mut [T; N];
+                let alloc = ptr::read(me.allocator());
+                Ok(Box::from_raw_in(buf, alloc))
+            }
+        } else {
+            Err(self)
+        }
     }
 
     /// Shortens the vector, keeping the first `len` elements and dropping