Rollup merge of #65389 - ecstatic-morse:zero-sized-array-no-drop, r=eddyb

Return `false` from `needs_drop` for all zero-sized arrays.

Resolves #65348.

This changes the result of the `needs_drop` query from `true` to `false` for types such as `[Box<i32>; 0]`. I believe this change to be sound because a zero-sized array can never actually hold a value. This is an elegant way of resolving #65348 and #64945, but obviously it has much broader implications.

1 files changed, 23 insertions, 0 deletions

diff --git a/src/test/ui/consts/issue-65348.rs b/src/test/ui/consts/issue-65348.rs
new file mode 100644
index 00000000000..5eafa831d63
--- /dev/null
+++ b/src/test/ui/consts/issue-65348.rs
@@ -0,0 +1,23 @@
+// check-pass
+
+struct Generic<T>(T);
+
+impl<T> Generic<T> {
+    const ARRAY: [T; 0] = [];
+    const NEWTYPE_ARRAY: Generic<[T; 0]> = Generic([]);
+    const ARRAY_FIELD: Generic<(i32, [T; 0])> = Generic((0, []));
+}
+
+pub const fn array<T>() ->  &'static T {
+    &Generic::<T>::ARRAY[0]
+}
+
+pub const fn newtype_array<T>() ->  &'static T {
+    &Generic::<T>::NEWTYPE_ARRAY.0[0]
+}
+
+pub const fn array_field<T>() ->  &'static T {
+    &(Generic::<T>::ARRAY_FIELD.0).1[0]
+}
+
+fn main() {}