Auto merge of #145457 - m-ou-se:default-array-zero, r=<try>

Experiment: Add `where T: Default` to `Default for [T; 0]` impl.

Author: rust-bors[bot]

library/core/src/array/mod.rs

@@ -484,7 +484,7 @@ macro_rules! array_impl_default {
     };
     {$n:expr,} => {
         #[stable(since = "1.4.0", feature = "array_default")]
-        impl<T> Default for [T; $n] {
+        impl<T> Default for [T; $n] where T: Default {
             fn default() -> [T; $n] { [] }
         }
     };

library/coretests/tests/array.rs

@@ -292,13 +292,6 @@ fn array_default_impl_avoids_leaks_on_panic() {
     assert_eq!(COUNTER.load(Relaxed), 0);
 }
 
-#[test]
-fn empty_array_is_always_default() {
-    struct DoesNotImplDefault;
-
-    let _arr = <[DoesNotImplDefault; 0]>::default();
-}
-
 #[test]
 fn array_map() {
     let a = [1, 2, 3];