or_patterns: add regression test for 68785

Author: Centril

src/test/ui/or-patterns/issue-68785-irrefutable-param-with-at.rs

@@ -0,0 +1,14 @@
+// check-pass
+
+#![feature(or_patterns)]
+
+enum MyEnum {
+    FirstCase(u8),
+    OtherCase(u16),
+}
+
+fn my_fn(x @ (MyEnum::FirstCase(_) | MyEnum::OtherCase(_)): MyEnum) {}
+
+fn main() {
+    my_fn(MyEnum::FirstCase(0));
+}