represent byte/bool closure as unit

compiler/mono/src/layout.rs

@@ -415,13 +415,10 @@ impl<'a> LambdaSet<'a> {
         use UnionVariant::*;
         match variant {
             Never => Layout::Union(UnionLayout::NonRecursive(&[])),
-            Unit | UnitWithArguments => Layout::Struct(&[]),
-            BoolUnion { .. } => {
-                // Layout::Builtin(Builtin::Int1),
-
+            Unit | UnitWithArguments | BoolUnion { .. } | ByteUnion(_) => {
+                // no useful information to store
                 Layout::Struct(&[])
             }
-            ByteUnion(_) => Layout::Builtin(Builtin::Int8),
             Newtype {
                 arguments: layouts, ..
             } => Layout::Struct(layouts.into_bump_slice()),

compiler/test_gen/src/gen_primitives.rs

@@ -2554,7 +2554,7 @@ fn mirror_llvm_alignment_padding() {
 }
 
 #[test]
-fn code_gen_unified_closure() {
+fn lambda_set_bool() {
     assert_evals_to!(
         indoc!(
             r#"
@@ -2576,3 +2576,28 @@ fn code_gen_unified_closure() {
         i64
     );
 }
+
+#[test]
+fn lambda_set_byte() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+                app "test" provides [ main ] to "./platform"
+
+                p1 = (\u -> u == 97)
+                p2 = (\u -> u == 98)
+                p3 = (\u -> u == 99)
+
+                main : I64
+                main =
+                    oneOfResult = List.map [p1, p2, p3] (\p -> p 42)
+
+                    when oneOfResult is
+                        _ -> 32
+
+            "#
+        ),
+        32,
+        i64
+    );
+}