Ambient lambda set unification means we can have nice things again

crates/compiler/late_solve/src/lib.rs

@@ -123,7 +123,10 @@ impl Phase for LatePhase<'_> {
 
                 let copied = module_types
                     .storage_subs
-                    .export_variable_to(target_subs, ambient_function);
+                    // TODO: I think this is always okay, but revisit later when we're in a more
+                    // stable position to see if we can get rid of the bookkeeping done as a result
+                    // of this.
+                    .export_variable_to_directly_to_use_site(target_subs, ambient_function);
                 let our_ambient_function_var = copied.variable;
 
                 debug_assert!(matches!(

crates/compiler/mono/src/layout.rs

@@ -1131,8 +1131,9 @@ fn resolve_lambda_set(subs: &Subs, mut var: Variable) -> ResolvedLambdaSet {
             }) => {
                 debug_assert!(
                     unspecialized.is_empty(),
-                    "unspecialized lambda sets left over during resolution: {:?}",
+                    "unspecialized lambda sets left over during resolution: {:?}, {:?}",
                     roc_types::subs::SubsFmtContent(subs.get_content_without_compacting(var), subs),
+                    subs.uls_of_var
                 );
                 roc_types::pretty_print::push_union(subs, solved, &mut set);
                 return ResolvedLambdaSet::Set(set);

crates/compiler/test_gen/src/gen_abilities.rs

@@ -353,3 +353,28 @@ fn encode_use_stdlib() {
         RocStr
     )
 }
+
+#[test]
+#[cfg(any(feature = "gen-llvm"))]
+fn encode_use_stdlib_without_wrapping_custom() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            app "test"
+                imports [Encode.{ toEncoder }, Json]
+                provides [main] to "./platform"
+
+            HelloWorld := {}
+            toEncoder = \@HelloWorld {} -> Encode.string "Hello, World!\n"
+
+            main =
+                result = Str.fromUtf8 (Encode.toBytes (@HelloWorld {}) Json.format)
+                when result is
+                    Ok s -> s
+                    _ -> "<bad>"
+            "#
+        ),
+        RocStr::from("\"Hello, World!\n\""),
+        RocStr
+    )
+}