remove EmptyStruct from wrapper

compiler/mono/src/alias_analysis.rs

@@ -885,10 +885,6 @@ fn expr_spec(
             let value_id = env.symbols[structure];
 
             match wrapped {
-                Wrapped::EmptyRecord => {
-                    // this is a unit value
-                    builder.add_make_tuple(block, &[])
-                }
                 Wrapped::SingleElementRecord => {
                     // builder.add_get_tuple_field(block, value_id, *index as u32)
                     Ok(env.symbols[structure])

compiler/mono/src/ir.rs

@@ -1016,7 +1016,6 @@ pub enum Literal<'a> {
 
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum Wrapped {
-    EmptyRecord,
     SingleElementRecord,
     RecordOrSingleTagUnion,
 }
@@ -1036,7 +1035,7 @@ impl Wrapped {
     pub fn opt_from_layout(layout: &Layout<'_>) -> Option<Self> {
         match layout {
             Layout::Struct(fields) => match fields.len() {
-                0 => Some(Wrapped::EmptyRecord),
+                0 => unreachable!(),
                 1 => Some(Wrapped::SingleElementRecord),
                 _ => Some(Wrapped::RecordOrSingleTagUnion),
             },
@@ -1048,7 +1047,7 @@ impl Wrapped {
                     Recursive(tags) | NonRecursive(tags) => match tags {
                         [] => todo!("how to handle empty tag unions?"),
                         [single] => match single.len() {
-                            0 => Some(Wrapped::EmptyRecord),
+                            0 => unreachable!(),
                             1 => Some(Wrapped::SingleElementRecord),
                             _ => Some(Wrapped::RecordOrSingleTagUnion),
                         },

compiler/test_gen/src/gen_primitives.rs

@@ -2488,3 +2488,44 @@ fn hit_unresolved_type_variable() {
         RocStr
     );
 }
+
+#[test]
+fn pattern_match_empty_record() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+                app "test" provides [ main ] to "./platform"
+
+                main : I64
+                main =
+                    when {} is
+                        {} -> 0
+
+            "#
+        ),
+        0,
+        i64
+    );
+}
+
+#[test]
+fn pattern_match_unit_tag() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+                app "test" provides [ main ] to "./platform"
+
+                unit : [ Unit ]
+                unit = Unit
+
+                main : I64
+                main =
+                    when unit is
+                        Unit -> 0
+
+            "#
+        ),
+        0,
+        i64
+    );
+}