tests(test_gen): add tests for mono

compiler/mono/src/ir.rs

@@ -2802,6 +2802,16 @@ pub fn with_hole<'a>(
             use crate::layout::UnionVariant::*;
             let arena = env.arena;
 
+            match layout_cache.from_var(arena, variant_var, env.subs) {
+                Err(e) => panic!("invalid layout {:?}", e),
+                Ok(Layout::FunctionPointer(argument_layouts, ret_layout)) => {
+                    dbg!(argument_layouts, ret_layout);
+                }
+                Ok(_) => {
+                    panic!("idk")
+                }
+            }
+
             let res_variant = crate::layout::union_sorted_tags(env.arena, variant_var, env.subs);
 
             let variant = match res_variant {

compiler/mono/src/layout.rs

@@ -1,6 +1,7 @@
 use crate::ir::Parens;
 use bumpalo::collections::Vec;
 use bumpalo::Bump;
+use core::panic;
 use roc_collections::all::{default_hasher, MutMap, MutSet};
 use roc_module::ident::{Lowercase, TagName};
 use roc_module::symbol::{Interns, Symbol};

compiler/test_gen/src/gen_list.rs

@@ -1803,3 +1803,19 @@ fn cleanup_because_exception() {
         RocList<bool>
     );
 }
+
+#[test]
+fn applied_tag_function() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            x : List [ Foo Str ]
+            x = List.map [ "a", "b" ] Foo
+
+            x
+            "#
+        ),
+        RocList::from_slice(&[false; 1]),
+        RocList<bool>
+    );
+}