moved renamed docs formatted | empty-allocation-non-null.rs

Author: Kivooeo

tests/ui/empty-allocation-non-null.rs renamed to tests/ui/allocator/empty-alloc-nonnull-guarantee.rs

@@ -1,3 +1,9 @@
+//! Test that empty allocations produce non-null pointers
+//!
+//! This test ensures that Rust's allocator maintains the invariant that
+//! Box<T> is always non-null, even for zero-sized types and empty allocations.
+//! This is crucial for memory safety guarantees in Rust.
+
 //@ run-pass
 
 pub fn main() {