Reproduce #4733

crates/compiler/test_mono/src/tests.rs

@@ -2173,3 +2173,22 @@ fn issue_4749() {
         "###
     )
 }
+
+#[mono_test(mode = "test", no_check)]
+fn issue_4733() {
+    indoc!(
+        r###"
+        interface Test exposes [] imports []
+
+        fn = \{} ->
+            instr : [ Op (U64, U64 -> U64) ]
+            instr = if Bool.true then (Op Num.mul) else (Op Num.add)
+
+            Op op = instr
+
+            \a -> op a a
+
+        expect ((fn {}) 3) == 9
+        "###
+    )
+}