simple implementation of NullableUnwrapped

compiler/gen/src/llvm/build.rs

@@ -9,8 +9,8 @@ use crate::llvm::build_str::{
 };
 use crate::llvm::compare::{build_eq, build_neq};
 use crate::llvm::convert::{
-    basic_type_from_builtin, basic_type_from_layout, block_of_memory, collection, get_fn_type,
+    basic_type_from_builtin, basic_type_from_layout, block_of_memory, block_of_memory_slices,
-    get_ptr_type, ptr_int,
+    collection, get_fn_type, get_ptr_type, ptr_int,
 };
 use crate::llvm::refcounting::{
     decrement_refcount_layout, increment_refcount_layout, refcount_is_one_comparison,
@@ -1136,6 +1136,109 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
             data_ptr.into()
         }
 
+        Tag {
+            arguments,
+            tag_layout:
+                Layout::Union(UnionLayout::NullableUnwrapped {
+                    nullable_id,
+                    other_fields,
+                    ..
+                }),
+            union_size,
+            tag_id,
+            tag_name,
+            ..
+        } => {
+            let tag_struct_type =
+                block_of_memory_slices(env.context, &[other_fields], env.ptr_bytes);
+
+            if *tag_id == *nullable_id as u8 {
+                let output_type = tag_struct_type.ptr_type(AddressSpace::Generic);
+
+                return output_type.const_null().into();
+            }
+
+            debug_assert!(*union_size > 1);
+            let ptr_size = env.ptr_bytes;
+
+            let ctx = env.context;
+            let builder = env.builder;
+
+            // Determine types
+            let num_fields = arguments.len() + 1;
+            let mut field_types = Vec::with_capacity_in(num_fields, env.arena);
+            let mut field_vals = Vec::with_capacity_in(num_fields, env.arena);
+
+            let tag_field_layouts = if let TagName::Closure(_) = tag_name {
+                // closures ignore (and do not store) the discriminant
+                panic!()
+            } else {
+                if (*tag_id != 0) == *nullable_id {
+                    &[] as &[_]
+                } else {
+                    other_fields
+                }
+            };
+
+            debug_assert_eq!(arguments.len(), tag_field_layouts.len());
+
+            for (field_symbol, tag_field_layout) in arguments.iter().zip(tag_field_layouts.iter()) {
+                let val = load_symbol(env, scope, field_symbol);
+
+                // Zero-sized fields have no runtime representation.
+                // The layout of the struct expects them to be dropped!
+                if !tag_field_layout.is_dropped_because_empty() {
+                    let field_type =
+                        basic_type_from_layout(env.arena, env.context, tag_field_layout, ptr_size);
+
+                    field_types.push(field_type);
+
+                    if let Layout::RecursivePointer = tag_field_layout {
+                        debug_assert!(val.is_pointer_value());
+
+                        // we store recursive pointers as `i64*`
+                        let ptr = cast_basic_basic(
+                            builder,
+                            val,
+                            ctx.i64_type().ptr_type(AddressSpace::Generic).into(),
+                        );
+
+                        field_vals.push(ptr);
+                    } else {
+                        // this check fails for recursive tag unions, but can be helpful while debugging
+                        // debug_assert_eq!(tag_field_layout, val_layout);
+
+                        field_vals.push(val);
+                    }
+                }
+            }
+
+            // Create the struct_type
+            let data_ptr = reserve_with_refcount(
+                env,
+                &Layout::Union(UnionLayout::NonRecursive(&[other_fields])),
+            );
+
+            let struct_type = ctx.struct_type(field_types.into_bump_slice(), false);
+            let struct_ptr = cast_basic_basic(
+                builder,
+                data_ptr.into(),
+                struct_type.ptr_type(AddressSpace::Generic).into(),
+            )
+            .into_pointer_value();
+
+            // Insert field exprs into struct_val
+            for (index, field_val) in field_vals.into_iter().enumerate() {
+                let field_ptr = builder
+                    .build_struct_gep(struct_ptr, index as u32, "struct_gep")
+                    .unwrap();
+
+                builder.build_store(field_ptr, field_val);
+            }
+
+            data_ptr.into()
+        }
+
         Tag { .. } => unreachable!("tags should have a Union or RecursiveUnion layout"),
 
         Reset(_) => todo!(),
@@ -1250,11 +1353,9 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
                 }
                 PointerValue(value) => {
                     match structure_layout {
-                        Layout::Union(UnionLayout::NullableWrapped {
+                        Layout::Union(UnionLayout::NullableWrapped { nullable_id, .. })
-                            nullable_id,
+                            if *index == 0 =>
-                            other_tags: fields,
+                        {
-                            ..
-                        }) if *index == 0 => {
                             let ptr = value;
                             let is_null = env.builder.build_is_null(ptr, "is_null");
 
@@ -1280,16 +1381,7 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
 
                             {
                                 env.builder.position_at_end(else_block);
-                                // if there is only one other tag besides then nullable_id, we know that id statically
+                                let tag_id = extract_tag_discriminant_ptr(env, ptr);
-                                let tag_id = if fields.len() == 1 {
-                                    if *nullable_id == 1 {
-                                        ctx.i64_type().const_int(0, false)
-                                    } else {
-                                        ctx.i64_type().const_int(1, false)
-                                    }
-                                } else {
-                                    extract_tag_discriminant_ptr(env, ptr)
-                                };
                                 env.builder.build_store(result, tag_id);
                                 env.builder.build_unconditional_branch(cont_block);
                             }
@@ -1298,6 +1390,23 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
 
                             env.builder.build_load(result, "load_result")
                         }
+                        Layout::Union(UnionLayout::NullableUnwrapped { nullable_id, .. })
+                            if *index == 0 =>
+                        {
+                            let is_null = env.builder.build_is_null(value, "is_null");
+
+                            let ctx = env.context;
+
+                            let then_value = ctx.i64_type().const_int(*nullable_id as u64, false);
+                            let else_value = ctx.i64_type().const_int(!*nullable_id as u64, false);
+
+                            env.builder.build_select(
+                                is_null,
+                                then_value,
+                                else_value,
+                                "select_tag_id",
+                            )
+                        }
                         _ => {
                             let ptr = cast_basic_basic(
                                 builder,

compiler/mono/src/decision_tree.rs

@@ -229,7 +229,7 @@ fn flatten<'a>(
             tag_name,
             layout,
         } if union.alternatives.len() == 1
-            && !matches!(layout, Layout::Union(UnionLayout::NullableWrapped { .. })) =>
+            && !matches!(layout, Layout::Union(UnionLayout::NullableWrapped { .. })| Layout::Union(UnionLayout::NullableUnwrapped { .. })) =>
         {
             // TODO ^ do we need to check that guard.is_none() here?
 
@@ -1020,9 +1020,8 @@ fn path_to_expr_help<'a>(
                                 use std::cmp::Ordering;
                                 dbg!(nullable_id, tag_id);
                                 match (*tag_id as usize).cmp(&(*nullable_id as usize)) {
-                                    Ordering::Equal =>
+                                    Ordering::Equal => {
-                                    // the nullable tag is going to predent it stores a tag id
+                                        // the nullable tag is going to pretend it stores a tag id
-                                    {
                                         &*env
                                             .arena
                                             .alloc([Layout::Builtin(crate::layout::TAG_SIZE)])
@@ -1033,16 +1032,15 @@ fn path_to_expr_help<'a>(
                             }
                             NullableUnwrapped {
                                 nullable_id,
-                                other_id: _,
                                 other_fields,
                             } => {
-                                let tag_id = *tag_id == 0;
+                                let tag_id = *tag_id != 0;
 
                                 if tag_id == *nullable_id {
-                                    // the nullable tag is going to predent it stores a tag id
+                                    // the nullable tag is going to pretend it stores a tag id
-                                    &[] as &[_]
+                                    &*env.arena.alloc([Layout::Builtin(crate::layout::TAG_SIZE)])
                                 } else {
-                                    other_fields
+                                    *other_fields
                                 }
                             }
                         }
@@ -1052,7 +1050,14 @@ fn path_to_expr_help<'a>(
                     other => env.arena.alloc([other.clone()]),
                 };
 
-                debug_assert!(*index < field_layouts.len() as u64);
+                debug_assert!(
+                    *index < field_layouts.len() as u64,
+                    "{} {:?} {:?} {:?}",
+                    index,
+                    field_layouts,
+                    &layout,
+                    tag_id,
+                );
 
                 let inner_layout = match &field_layouts[*index as usize] {
                     Layout::RecursivePointer => layout.clone(),

compiler/mono/src/ir.rs

@@ -2838,7 +2838,42 @@ pub fn with_hole<'a>(
 
                             (tag, layout)
                         }
-                        NullableUnwrapped { .. } => todo!(),
+                        NullableUnwrapped {
+                            nullable_id,
+                            nullable_name: _,
+                            other_name: _,
+                            other_fields,
+                        } => {
+                            // FIXME drop tag
+                            let tag_id_symbol = env.unique_symbol();
+                            opt_tag_id_symbol = Some(tag_id_symbol);
+
+                            field_symbols = {
+                                let mut temp =
+                                    Vec::with_capacity_in(field_symbols_temp.len() + 1, arena);
+                                // FIXME drop tag
+                                temp.push(tag_id_symbol);
+
+                                temp.extend(field_symbols_temp.iter().map(|r| r.1));
+
+                                temp.into_bump_slice()
+                            };
+
+                            let layout = Layout::Union(UnionLayout::NullableUnwrapped {
+                                nullable_id,
+                                other_fields,
+                            });
+
+                            let tag = Expr::Tag {
+                                tag_layout: layout.clone(),
+                                tag_name,
+                                tag_id: tag_id as u8,
+                                union_size,
+                                arguments: field_symbols,
+                            };
+
+                            (tag, layout)
+                        }
                     };
 
                     let mut stmt = Stmt::Let(assigned, tag, layout, hole);
@@ -6182,7 +6217,68 @@ fn from_can_pattern_help<'a>(
                             }
                         }
 
-                        NullableUnwrapped { .. } => todo!(),
+                        NullableUnwrapped {
+                            other_fields,
+                            nullable_id,
+                            nullable_name,
+                            other_name: _,
+                        } => {
+                            debug_assert!(!other_fields.is_empty());
+
+                            dbg!(nullable_id, &nullable_name);
+
+                            ctors.push(Ctor {
+                                tag_id: TagId(nullable_id as u8),
+                                name: nullable_name.clone(),
+                                arity: 0,
+                            });
+
+                            ctors.push(Ctor {
+                                tag_id: TagId(!nullable_id as u8),
+                                name: nullable_name.clone(),
+                                // FIXME drop tag
+                                arity: other_fields.len() - 1,
+                            });
+
+                            let union = crate::exhaustive::Union {
+                                render_as: RenderAs::Tag,
+                                alternatives: ctors,
+                            };
+
+                            let mut mono_args = Vec::with_capacity_in(arguments.len(), env.arena);
+
+                            let it = if tag_name == &nullable_name {
+                                [].iter()
+                            } else {
+                                // FIXME drop tag
+                                argument_layouts[1..].iter()
+                            };
+
+                            for ((_, loc_pat), layout) in arguments.iter().zip(it) {
+                                mono_args.push((
+                                    from_can_pattern_help(
+                                        env,
+                                        layout_cache,
+                                        &loc_pat.value,
+                                        assignments,
+                                    )?,
+                                    layout.clone(),
+                                ));
+                            }
+
+                            let layout = Layout::Union(UnionLayout::NullableUnwrapped {
+                                nullable_id,
+                                other_fields,
+                            });
+
+                            Pattern::AppliedTag {
+                                tag_name: tag_name.clone(),
+                                tag_id: tag_id as u8,
+                                arguments: mono_args,
+                                union,
+                                layout,
+                            }
+                        }
                     }
                 }
             };

compiler/mono/src/layout.rs

@@ -56,7 +56,6 @@ pub enum UnionLayout<'a> {
     /// e.g. `ConsList a : [ Nil, Cons a (ConsList a) ]`
     NullableUnwrapped {
         nullable_id: bool,
-        other_id: bool,
         other_fields: &'a [Layout<'a>],
     },
 }
@@ -1104,13 +1103,11 @@ fn layout_from_flat_type<'a>(
 
             let union_layout = if let Some(tag_id) = nullable {
                 match tag_layouts.into_bump_slice() {
-                    [one] if false => {
+                    [one] => {
-                        let nullable_id = tag_id == 0;
+                        let nullable_id = tag_id != 0;
-                        let other_id = !nullable_id;
 
                         UnionLayout::NullableUnwrapped {
                             nullable_id,
-                            other_id,
                             other_fields: one,
                         }
                     }
@@ -1224,11 +1221,10 @@ pub enum WrappedVariant<'a> {
         sorted_tag_layouts: Vec<'a, (TagName, &'a [Layout<'a>])>,
     },
     NullableUnwrapped {
-        nullable_id: i64,
+        nullable_id: bool,
         nullable_name: TagName,
-        other_id: i64,
         other_name: TagName,
-        other_arguments: &'a [Layout<'a>],
+        other_fields: &'a [Layout<'a>],
     },
 }
 
@@ -1274,16 +1270,15 @@ impl<'a> WrappedVariant<'a> {
             NullableUnwrapped {
                 nullable_id,
                 nullable_name,
-                other_id,
                 other_name,
-                other_arguments,
+                other_fields,
             } => {
                 if tag_name == nullable_name {
                     (*nullable_id as u8, &[] as &[_])
                 } else {
                     debug_assert_eq!(other_name, tag_name);
 
-                    (*other_id as u8, other_arguments.clone())
+                    (!*nullable_id as u8, other_fields.clone())
                 }
             }
         }
@@ -1504,10 +1499,22 @@ pub fn union_sorted_tags_help<'a>(
                 }
                 _ => {
                     let variant = if let Some((nullable_id, nullable_name)) = nullable {
-                        WrappedVariant::NullableWrapped {
+                        if answer.len() == 1 {
-                            nullable_id,
+                            let (other_name, other_arguments) = answer.drain(..).next().unwrap();
-                            nullable_name,
+                            let nullable_id = nullable_id != 0;
-                            sorted_tag_layouts: answer,
+
+                            WrappedVariant::NullableUnwrapped {
+                                nullable_id,
+                                nullable_name,
+                                other_name,
+                                other_fields: other_arguments,
+                            }
+                        } else {
+                            WrappedVariant::NullableWrapped {
+                                nullable_id,
+                                nullable_name,
+                                sorted_tag_layouts: answer,
+                            }
                         }
                     } else if is_recursive {
                         WrappedVariant::Recursive {