Reproduce #4733

crates/compiler/test_mono/generated/issue_4733.txt

@@ -0,0 +1,49 @@
+procedure Bool.11 (#Attr.2, #Attr.3):
+    let Bool.23 : Int1 = lowlevel Eq #Attr.2 #Attr.3;
+    ret Bool.23;
+
+procedure Bool.2 ():
+    let Bool.24 : Int1 = true;
+    ret Bool.24;
+
+procedure Num.19 (#Attr.2, #Attr.3):
+    let Num.256 : U64 = lowlevel NumAdd #Attr.2 #Attr.3;
+    ret Num.256;
+
+procedure Num.21 (#Attr.2, #Attr.3):
+    let Num.257 : U64 = lowlevel NumMul #Attr.2 #Attr.3;
+    ret Num.257;
+
+procedure Test.0 (Test.8):
+    let Test.23 : Int1 = CallByName Bool.2;
+    if Test.23 then
+        let Test.24 : {} = Struct {};
+        ret Test.24;
+    else
+        let Test.22 : {} = Struct {};
+        ret Test.22;
+
+procedure Test.5 (Test.6, Test.2):
+    joinpoint Test.19 Test.18:
+        ret Test.18;
+    in
+    switch Test.2:
+        case 0:
+            let Test.20 : U64 = CallByName Num.19 Test.6 Test.6;
+            jump Test.19 Test.20;
+    
+        default:
+            let Test.21 : U64 = CallByName Num.21 Test.6 Test.6;
+            jump Test.19 Test.21;
+    
+
+procedure Test.7 ():
+    let Test.13 : U64 = 3i64;
+    let Test.15 : {} = Struct {};
+    let Test.14 : Int1 = CallByName Test.0 Test.15;
+    let Test.11 : U64 = CallByName Test.5 Test.13 Test.14;
+    let Test.12 : U64 = 9i64;
+    let Test.10 : Int1 = CallByName Bool.11 Test.11 Test.12;
+    expect Test.10;
+    let Test.9 : {} = Struct {};
+    ret Test.9;

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
+        "###
+    )
+}