Add gen test for recursion var resolved upon specialization

crates/compiler/test_gen/src/gen_primitives.rs

@@ -4335,3 +4335,26 @@ fn when_guard_appears_multiple_times_in_compiled_decision_tree_issue_5176() {
         u8
     )
 }
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn recursive_lambda_set_resolved_only_upon_specialization() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            app "test" provides [main] to "./platform"
+
+            factCPS = \n, cont ->
+                if n == 0 then
+                    cont 1
+                else
+                    factCPS (n - 1) \value -> cont (n * value)
+
+            main =
+                factCPS 5u64 \x -> x
+            "#
+        ),
+        120,
+        u64
+    );
+}