From 8deb377d30128eebd96090725b3a63705b904aa0 Mon Sep 17 00:00:00 2001
From: Eric Correia <correia.eh@gmail.com>
Date: Sat, 3 Jul 2021 12:06:48 -0400
Subject: [PATCH 1/2] tag must be its own type fix

---
 compiler/mono/src/ir.rs           | 21 +++++++++++----------
 compiler/test_gen/src/gen_tags.rs | 17 +++++++++++++++++
 2 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/compiler/mono/src/ir.rs b/compiler/mono/src/ir.rs
index 94877e4ad0..9729d7b27d 100644
--- a/compiler/mono/src/ir.rs
+++ b/compiler/mono/src/ir.rs
@@ -4126,17 +4126,18 @@ fn convert_tag_union<'a>(
             hole,
         ),
         ByteUnion(tag_names) => {
-            let tag_id = tag_names
-                .iter()
-                .position(|key| key == &tag_name)
-                .expect("tag must be in its own type");
+            let opt_tag_id = tag_names.iter().position(|key| key == &tag_name);
+            // .expect("tag must be in its own type");
 
-            Stmt::Let(
-                assigned,
-                Expr::Literal(Literal::Byte(tag_id as u8)),
-                Layout::Builtin(Builtin::Int8),
-                hole,
-            )
+            match opt_tag_id {
+                Some(tag_id) => Stmt::Let(
+                    assigned,
+                    Expr::Literal(Literal::Byte(tag_id as u8)),
+                    Layout::Builtin(Builtin::Int8),
+                    hole,
+                ),
+                None => Stmt::RuntimeError("tag must be in its own type"),
+            }
         }
 
         Newtype {
diff --git a/compiler/test_gen/src/gen_tags.rs b/compiler/test_gen/src/gen_tags.rs
index 776c06ff07..cfd11b807f 100644
--- a/compiler/test_gen/src/gen_tags.rs
+++ b/compiler/test_gen/src/gen_tags.rs
@@ -1033,3 +1033,20 @@ fn applied_tag_function_linked_list() {
         i64
     );
 }
+
+#[test]
+#[should_panic(expected = "")]
+fn tag_must_be_its_own_type() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            z : [ A, B, C ]
+            z = Z
+
+            z
+            "#
+        ),
+        1,
+        i64
+    );
+}

From aa123635fa23c022f24f8b285ee04efc88df4e27 Mon Sep 17 00:00:00 2001
From: Eric Correia <correia.eh@gmail.com>
Date: Sat, 3 Jul 2021 12:08:42 -0400
Subject: [PATCH 2/2] remove comment

---
 compiler/mono/src/ir.rs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/compiler/mono/src/ir.rs b/compiler/mono/src/ir.rs
index 9729d7b27d..87080476cb 100644
--- a/compiler/mono/src/ir.rs
+++ b/compiler/mono/src/ir.rs
@@ -4127,7 +4127,6 @@ fn convert_tag_union<'a>(
         ),
         ByteUnion(tag_names) => {
             let opt_tag_id = tag_names.iter().position(|key| key == &tag_name);
-            // .expect("tag must be in its own type");
 
             match opt_tag_id {
                 Some(tag_id) => Stmt::Let(