rustc_codegen_ssa: Fix for codegen_get_discr

When doing the optimized implementation of getting the discriminant, the
arithmetic needs to be done in the tag type so wrapping behavior works
correctly.

Fixes #104519

1 files changed, 36 insertions, 0 deletions

diff --git a/src/test/ui/enum-discriminant/issue-104519.rs b/src/test/ui/enum-discriminant/issue-104519.rs
new file mode 100644
index 00000000000..c4630f76b3a
--- /dev/null
+++ b/src/test/ui/enum-discriminant/issue-104519.rs
@@ -0,0 +1,36 @@
+// run-pass
+#![allow(dead_code)]
+
+enum OpenResult {
+    Ok(()),
+    Err(()),
+    TransportErr(TransportErr),
+}
+
+#[repr(i32)]
+enum TransportErr {
+    UnknownMethod = -2,
+}
+
+#[inline(never)]
+fn some_match(result: OpenResult) -> u8 {
+    match result {
+        OpenResult::Ok(()) => 0,
+        _ => 1,
+    }
+}
+
+fn main() {
+    let result = OpenResult::Ok(());
+    assert_eq!(some_match(result), 0);
+
+    let result = OpenResult::Ok(());
+    match result {
+        OpenResult::Ok(()) => (),
+        _ => unreachable!("message a"),
+    }
+    match result {
+        OpenResult::Ok(()) => (),
+        _ => unreachable!("message b"),
+    }
+}