Thread simple model of "ErasedLambdas" through proc layouts

But none of these paths are yet exercised.

crates/compiler/uitest/src/mono.rs

@@ -8,20 +8,22 @@ use roc_mono::{
     ir::{Proc, ProcLayout},
     layout::STLayoutInterner,
 };
-use roc_solve::FunctionKind;
 use tempfile::tempdir;
 use test_solve_helpers::format_problems;
 
+use crate::CompilerSettings;
+
 #[derive(Default)]
-pub struct MonoOptions {
+pub(crate) struct MonoOptions {
     pub no_check: bool,
 }
 
-pub fn write_compiled_ir<'a>(
+pub(crate) fn write_compiled_ir<'a>(
     writer: &mut impl io::Write,
     test_module: &str,
     dependencies: impl IntoIterator<Item = (&'a str, &'a str)>,
     options: MonoOptions,
+    compiler_settings: CompilerSettings,
     allow_can_errors: bool,
 ) -> io::Result<()> {
     use roc_packaging::cache::RocCacheDir;
@@ -42,8 +44,7 @@ pub fn write_compiled_ir<'a>(
 
     let load_config = LoadConfig {
         target_info: roc_target::TargetInfo::default_x86_64(),
-        // TODO parameterize
-        function_kind: FunctionKind::LambdaSet,
+        function_kind: compiler_settings.function_kind,
         threading: Threading::Single,
         render: roc_reporting::report::RenderTarget::Generic,
         palette: roc_reporting::report::DEFAULT_PALETTE,

crates/compiler/uitest/src/uitest.rs

@@ -128,6 +128,7 @@ fn run_test(path: PathBuf) -> Result<(), Failed> {
             &mut fd,
             program,
             inferred_program,
+            compiler_settings,
             can_options,
             mono_options,
             emit_options,
@@ -363,6 +364,7 @@ fn assemble_query_output(
     writer: &mut impl io::Write,
     program: Modules<'_>,
     inferred_program: InferredProgram,
+    compiler_settings: CompilerSettings,
     can_options: CanOptions,
     mono_options: MonoOptions,
     emit_options: EmitOptions,
@@ -411,6 +413,7 @@ fn assemble_query_output(
             test_module,
             other_modules,
             mono_options,
+            compiler_settings,
             can_options.allow_errors,
         )?;
     }

crates/compiler/uitest/tests/lambda_set/erased/multi_branch_capturing.txt

@@ -1,5 +1,6 @@
 # +set function_kind=erased
-interface Test exposes [main] imports []
+# +emit:mono
+app "test" provides [main] to "./platform"
 
 f = \s ->
   if Bool.true
@@ -8,5 +9,7 @@ f = \s ->
   else \{} -> s
   #    ^^^^^^^^ {}* -[[#Attr.#Erased(33)]]-> Str
 
-main = f ""
-#^^^^{-1} {}w_a -[[#Attr.#Erased(33)]]-> Str
+main = (f "") {}
+#       ^^^^ {} -[[#Attr.#Erased(33)]]-> Str
+
+# -emit:mono