Add test for ignored pattern

schala-lang/language/src/eval.rs

@@ -563,4 +563,15 @@ if a { is true -> "x", is false -> "y" }
 "#;
     test_in_fresh_env!(source, "\"y\"");
   }
+
+  #[test]
+  fn ignore_pattern() {
+    let source = r#"
+type Option<T> = Some(T) | None
+if Some(10) {
+  is _ -> "hella"
+}
+"#;
+    test_in_fresh_env!(source, "\"hella\"");
+  }
 }