not bootstrap

Author: MikailBag

library/core/src/array/mod.rs

@@ -354,6 +354,7 @@ impl<T: Ord, const N: usize> Ord for [T; N] {
 }
 
 /// This module implements `Default` for arrays.
+#[cfg(not(bootstrap))]
 mod default_impls {
     // A trait implemented by all arrays which are either empty or contain a type implementing `Default`.
     #[unstable(
@@ -399,14 +400,37 @@ mod default_impls {
         [T; N]: ArrayDefault,
     {
         fn default() -> [T; N] {
-            assert_eq!(std::mem::size_of::<[(); N]>(), 0);
+            assert_eq!(crate::mem::size_of::<[(); N]>(), 0);
             // SAFETY: it is always valid to use `zeroed` for zero-sized value.
-            let arr: [(); N] = unsafe { std::mem::zeroed() };
+            let arr: [(); N] = unsafe { crate::mem::zeroed() };
             arr.map(|_unit| DefaultHack::default_hack())
         }
     }
 }
 
+#[cfg(bootstrap)]
+mod default_impls {
+    macro_rules! array_impl_default {
+        {$n:expr, $t:ident $($ts:ident)*} => {
+            #[stable(since = "1.4.0", feature = "array_default")]
+            impl<T> Default for [T; $n] where T: Default {
+                fn default() -> [T; $n] {
+                    [$t::default(), $($ts::default()),*]
+                }
+            }
+            array_impl_default!{($n - 1), $($ts)*}
+        };
+        {$n:expr,} => {
+            #[stable(since = "1.4.0", feature = "array_default")]
+            impl<T> Default for [T; $n] {
+                fn default() -> [T; $n] { [] }
+            }
+        };
+    }
+    
+    array_impl_default! {16, T T T T T T T T T T T T T T T T}
+}
+
 
 #[lang = "array"]
 impl<T, const N: usize> [T; N] {

library/core/src/lib.rs

@@ -64,7 +64,7 @@
 #![allow(explicit_outlives_requirements)]
 #![allow(incomplete_features)]
 #![feature(allow_internal_unstable)]
-#![feature(array_default_internals)]
+#![cfg_attr(not(bootstrap), feature(array_default_internals))]
 #![feature(arbitrary_self_types)]
 #![feature(asm)]
 #![feature(cfg_target_has_atomic)]