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Glue body for recursive single-tag unions

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Richard Feldman 2022-08-07 18:12:32 -04:00
parent 6e7f0210da
commit 22b219c3c9
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2 changed files with 64 additions and 25 deletions
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79
crates/glue/src/rust_glue.rs
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@ -248,14 +248,35 @@ fn add_type(target_info: TargetInfo, id: TypeId, types: &Types, impls: &mut Impl
RocTagUnion::RecursiveSingleTag {
name,
tag_name,
payload,
payload: payload_id,
}
| RocTagUnion::NonRecursiveSingleTag {
name,
tag_name,
payload: Some(payload),
payload: Some(payload_id),
} => {
todo!();
// Store single-tag unions as structs rather than enums,
// because they have only one alternative. However, still
// offer the usual tag union APIs.
{
let derive = derive_str(
&RocType::Struct {
// Deriving doesn't depend on the struct's name,
// so no need to clone name here.
name: String::new(),
fields: vec![(tag_name.clone(), *payload_id)],
},
types,
false,
);
let mut buf = format!("#[repr(C)]\n{derive}\npub struct {name} {{");
write_tag_union_field(tag_name, &Some(*payload_id), types, &mut buf);
buf.push_str("}\n");
add_decl(impls, None, target_info, buf);
}
}
RocTagUnion::NonRecursiveSingleTag {
name,
@ -465,27 +486,7 @@ pub struct {name} {{
let mut buf = format!("#[repr(C)]\n{pub_str}union {decl_union_name} {{\n");
for (tag_name, opt_payload_id) in tags {
// If there's no payload, we don't need a discriminant for it.
if let Some(payload_id) = opt_payload_id {
let payload_type = types.get_type(*payload_id);
write!(buf, "{INDENT}{tag_name}: ").unwrap();
if cannot_derive_copy(payload_type, types) {
// types with pointers need ManuallyDrop
// because rust unions don't (and can't)
// know how to drop them automatically!
writeln!(
buf,
"core::mem::ManuallyDrop<{}>,",
type_name(*payload_id, types)
)
.unwrap();
} else {
buf.push_str(&type_name(*payload_id, types));
buf.push_str(",\n");
}
}
write_tag_union_field(tag_name, opt_payload_id, types, &mut buf);
}
if tags.len() > 1 {
@ -1277,6 +1278,36 @@ pub struct {name} {{
}
}
#[inline(always)]
fn write_tag_union_field(
tag_name: &str,
opt_payload_id: &Option<TypeId>,
types: &Types,
buf: &mut String,
) {
// If there's no payload, we don't need a discriminant for it.
if let Some(payload_id) = opt_payload_id {
let payload_type = types.get_type(*payload_id);
write!(buf, "{INDENT}{tag_name}: ").unwrap();
if cannot_derive_copy(payload_type, types) {
// types with pointers need ManuallyDrop
// because rust unions don't (and can't)
// know how to drop them automatically!
writeln!(
buf,
"core::mem::ManuallyDrop<{}>,",
type_name(*payload_id, types)
)
.unwrap();
} else {
buf.push_str(&type_name(*payload_id, types));
buf.push_str(",\n");
}
}
}
fn write_impl_tags<
'a,
I: IntoIterator<Item = &'a (String, Option<TypeId>)>,