Add a regression test for issue-66501

Author: JohnTitor

src/test/ui/pattern/issue-66501.rs

@@ -0,0 +1,12 @@
+// check-pass
+
+#![allow(unreachable_patterns)]
+
+fn main() {
+    const CONST: &[Option<()>; 1] = &[Some(())];
+    match &[Some(())] {
+        &[None] => {}
+        CONST => {}
+        &[Some(())] => {}
+    }
+}