Add 81270

Issue: rust-lang/rust#81270

ices/81270.rs

@@ -0,0 +1,27 @@
+#![feature(allocator_api)]
+use std::alloc::{AllocError, Allocator, Global, Layout};
+use std::marker::PhantomData;
+use std::ptr::NonNull;
+
+struct S<A> {
+    a: PhantomData<A>,
+    b: [u8; 1],
+}
+unsafe impl<A> Allocator for S<A> {
+    fn allocate(&self, _: Layout) -> Result<NonNull<[u8]>, AllocError> {
+        todo!();
+    }
+    unsafe fn deallocate(&self, _: NonNull<u8>, _: Layout) {
+        todo!();
+    }
+}
+
+fn main() {
+    let x: Box<u8, S<u8>> = Box::new_in(
+        0,
+        S {
+            a: PhantomData,
+            b: [0; 1],
+        },
+    );
+}