From 3fa137d19fa5320059e15e0815afa991068654fa Mon Sep 17 00:00:00 2001
From: Richard Feldman <oss@rtfeldman.com>
Date: Fri, 13 May 2022 23:09:21 -0400
Subject: [PATCH] Revert "Bindgen single-field record and unions as unwrapped"

This reverts commit 4c2e6471a63fa61f04856810e5f06335392eaff5.
---
 bindgen/src/bindgen.rs  | 47 ++++++++++++++++-------------------------
 bindgen/tests/gen_rs.rs |  8 ++++++-
 2 files changed, 25 insertions(+), 30 deletions(-)

diff --git a/bindgen/src/bindgen.rs b/bindgen/src/bindgen.rs
index 0b1267334e..fee86f0954 100644
--- a/bindgen/src/bindgen.rs
+++ b/bindgen/src/bindgen.rs
@@ -79,12 +79,20 @@ pub fn add_type_help<'a>(
 
             add_tag_union(env, opt_name, tag_vars, var, Some(*rec_var), types)
         }
-        Content::Structure(FlatType::Apply(_symbol, _)) => match layout {
-            Layout::Builtin(builtin) => add_builtin_type(env, builtin, var, opt_name, types),
-            _ => {
+        Content::Structure(FlatType::Apply(symbol, _)) => {
+            if symbol.is_builtin() {
+                match layout {
+                    Layout::Builtin(builtin) => {
+                        add_builtin_type(env, builtin, var, opt_name, types)
+                    }
+                    _ => {
+                        unreachable!()
+                    }
+                }
+            } else {
                 todo!("Handle non-builtin Apply")
             }
-        },
+        }
         Content::Structure(FlatType::Func(_, _, _)) => {
             todo!()
         }
@@ -187,33 +195,13 @@ fn add_struct<I: IntoIterator<Item = (Lowercase, Variable)>>(
     types: &mut Types,
 ) -> TypeId {
     let subs = env.subs;
-    let fields_iter = &mut fields.into_iter();
-    let first_field = match fields_iter.next() {
-        Some(field) => field,
-        None => {
-            // This is an empty record; there's no more work to do!
-            return types.add(RocType::Struct {
-                name,
-                fields: Vec::new(),
-            });
-        }
-    };
-    let second_field = match fields_iter.next() {
-        Some(field) => field,
-        None => {
-            // This is a single-field record; unwrap that field.
-            return add_type(env, first_field.1, types);
-        }
-    };
+    let fields_iter = fields.into_iter();
     let mut sortables = bumpalo::collections::Vec::with_capacity_in(
-        2 + fields_iter.size_hint().1.unwrap_or_default(),
+        fields_iter.size_hint().1.unwrap_or_default(),
         env.arena,
     );
 
-    for (label, field_var) in std::iter::once(first_field)
-        .chain(std::iter::once(second_field))
-        .chain(fields_iter)
-    {
+    for (label, field_var) in fields_iter {
         sortables.push((
             label,
             field_var,
@@ -295,10 +283,11 @@ fn add_tag_union(
             }
             1 => {
                 // This is a single-tag union with 1 payload field, e.g.`[ Foo Str ]`.
-                // We'll just unwrap that.
+                // We'll just wrap that.
                 let var = *payload_vars.get(0).unwrap();
+                let content = add_type(env, var, types);
 
-                add_type(env, var, types)
+                types.add(RocType::TransparentWrapper { name, content })
             }
             _ => {
                 // This is a single-tag union with multiple payload field, e.g.`[ Foo Str U32 ]`.
diff --git a/bindgen/tests/gen_rs.rs b/bindgen/tests/gen_rs.rs
index 6b25efa435..8dc2921189 100644
--- a/bindgen/tests/gen_rs.rs
+++ b/bindgen/tests/gen_rs.rs
@@ -497,7 +497,13 @@ fn single_tag_union_with_one_payload_field() {
         generate_bindings(module)
             .strip_prefix('\n')
             .unwrap_or_default(),
-        "" // This shoud get completely unwrapped into nothing
+        indoc!(
+            r#"
+                #[derive(Clone, Debug, Default, Eq, Ord, Hash, PartialEq, PartialOrd)]
+                #[repr(transparent)]
+                pub struct UserId(roc_std::RocStr);
+            "#
+        )
     );
 }