language-servers/roc
1
0
Fork 0
mirror of https://github.com/roc-lang/roc.git synced 2025-08-18 19:10:18 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 7

Prefer keeping recursion var when merging tag union payloads

Browse source
This commit is contained in:
Ayaz Hafiz 2022-07-14 15:56:18 -04:00
parent 7433cc5c95
commit 6611cce22c
No known key found for this signature in database
GPG key ID: 0E2A37416A25EF58
1 changed files with 15 additions and 26 deletions
Download patch file Download diff file Expand all files Collapse all files

41
crates/compiler/unify/src/unify.rs
View file

@ -881,15 +881,7 @@ fn unify_structure<M: MetaCollector>(
RecursionVar { structure, .. } => match flat_type {
FlatType::TagUnion(_, _) => {
// unify the structure with this unrecursive tag union
let mut outcome = unify_pool(subs, pool, ctx.first, *structure, ctx.mode);
if outcome.mismatches.is_empty() {
outcome.union(fix_tag_union_recursion_variable(
subs, ctx, ctx.first, other,
));
}
outcome
unify_pool(subs, pool, ctx.first, *structure, ctx.mode)
}
FlatType::RecursiveTagUnion(rec, _, _) => {
debug_assert!(is_recursion_var(subs, *rec));
@ -898,15 +890,7 @@ fn unify_structure<M: MetaCollector>(
}
FlatType::FunctionOrTagUnion(_, _, _) => {
// unify the structure with this unrecursive tag union
let mut outcome = unify_pool(subs, pool, ctx.first, *structure, ctx.mode);
if outcome.mismatches.is_empty() {
outcome.union(fix_tag_union_recursion_variable(
subs, ctx, ctx.first, other,
));
}
outcome
unify_pool(subs, pool, ctx.first, *structure, ctx.mode)
}
// Only tag unions can be recursive; everything else is an error.
_ => mismatch!(
@ -2060,14 +2044,19 @@ fn unify_shared_tags_new<M: MetaCollector>(
outcome.union(unify_pool(subs, pool, actual, expected, ctx.mode));
// clearly, this is very suspicious: these variables have just been unified. And yet,
// not doing this leads to stack overflows
if let Rec::Right(_) = recursion_var {
if outcome.mismatches.is_empty() {
matching_vars.push(expected);
}
} else if outcome.mismatches.is_empty() {
matching_vars.push(actual);
if outcome.mismatches.is_empty() {
// If one of the variables is a recursion var, keep that one, so that we avoid inlining
// a recursive tag union type content where we should have a recursion var instead.
let merged_var = match (
(actual, subs.get_content_unchecked(actual)),
(expected, subs.get_content_unchecked(expected)),
) {
((var, Content::RecursionVar { .. }), _)
| (_, (var, Content::RecursionVar { .. })) => var,
_ => actual,
};
matching_vars.push(merged_var);
}
}