Add regression test for #68408

src/test/ui/lint/dead-code/issue-68408-false-positive.rs

@@ -0,0 +1,22 @@
+// check-pass
+
+// Make sure we don't have any false positives here.
+
+#![deny(dead_code)]
+
+enum X {
+    A { _a: () },
+    B { _b: () },
+}
+impl X {
+    fn a() -> X {
+        X::A { _a: () }
+    }
+    fn b() -> Self {
+        Self::B { _b: () }
+    }
+}
+
+fn main() {
+    let (_, _) = (X::a(), X::b());
+}