enum niche allocation grows toward zero if possible

1 files changed, 14 insertions, 0 deletions

diff --git a/src/test/ui/enum-discriminant/niche-prefer-zero.rs b/src/test/ui/enum-discriminant/niche-prefer-zero.rs
new file mode 100644
index 00000000000..f20607a8903
--- /dev/null
+++ b/src/test/ui/enum-discriminant/niche-prefer-zero.rs
@@ -0,0 +1,14 @@
+// Check that niche selection prefers zero.
+// See https://github.com/rust-lang/rust/pull/87794
+// run-pass
+#[repr(u8)]
+pub enum Size {
+    One = 1,
+    Two = 2,
+    Three = 3,
+}
+
+fn main() {
+    // check that `None` is zero
+    assert_eq!(0, unsafe { std::mem::transmute::<Option<Size>, u8>(None) });
+}