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Close extension types extended wiht uninhabited types after their extension

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This commit is contained in:
Ayaz Hafiz 2022-10-25 16:14:44 -05:00
parent 4d48ea7c2f
commit f3623b1e47
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GPG Key ID: 0E2A37416A25EF58
2 changed files with 60 additions and 4 deletions
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18
crates/compiler/solve/tests/solve_expr.rs
View File

@ -8149,4 +8149,22 @@ mod solve_expr {
"x -> x | x has Hash & Encoding & Decoding",
);
}
#[test]
fn extend_uninhabited_without_opening_union() {
infer_queries!(
indoc!(
r#"
app "test" provides [main] to "./platform"
walkHelp : {} -> [Continue {}, Break []]
main = when walkHelp {} is
# ^^^^^^^^^^^
Continue {} -> {}
"#
),
@"walkHelp {} : [Break [], Continue {}]"
);
}
}

46
crates/compiler/unify/src/unify.rs
View File

@ -2209,6 +2209,27 @@ fn should_extend_ext_with_uninhabited_type(
) && !subs.is_inhabited(candidate_type)
}
/// After extending an empty tag union extension type [with uninhabited
/// variants][should_extend_ext_with_uninhabited_type], the extension type must be closed again.
fn close_uninhabited_extended_union(subs: &mut Subs, mut var: Variable) {
loop {
match subs.get_content_without_compacting(var) {
Structure(FlatType::EmptyTagUnion) => {
return;
}
FlexVar(..) | FlexAbleVar(..) => {
subs.set_content_unchecked(var, Structure(FlatType::EmptyTagUnion));
return;
}
Structure(FlatType::TagUnion(_, ext))
| Structure(FlatType::RecursiveTagUnion(_, _, ext)) => {
var = *ext;
}
_ => internal_error!("not a tag union"),
}
}
}
#[allow(clippy::too_many_arguments)]
#[must_use]
fn unify_tag_unions<M: MetaCollector>(
@ -2289,7 +2310,9 @@ fn unify_tag_unions<M: MetaCollector>(
// SPECIAL-CASE: if we can grow empty extensions with uninhabited types,
// patch `ext1` to grow accordingly.
if should_extend_ext_with_uninhabited_type(env.subs, ext1, extra_tags_in_2) {
let extend_ext_with_uninhabited =
should_extend_ext_with_uninhabited_type(env.subs, ext1, extra_tags_in_2);
if extend_ext_with_uninhabited {
let new_ext = fresh(env, pool, ctx, Content::FlexVar(None));
let new_union = Structure(FlatType::TagUnion(tags1, new_ext));
let mut new_desc = ctx.first_desc;
@ -2317,6 +2340,10 @@ fn unify_tag_unions<M: MetaCollector>(
shared_tags_outcome.union(ext_outcome);
if extend_ext_with_uninhabited {
close_uninhabited_extended_union(env.subs, ctx.first);
}
shared_tags_outcome
}
} else if separate.only_in_2.is_empty() {
@ -2329,10 +2356,12 @@ fn unify_tag_unions<M: MetaCollector>(
let mut total_outcome = Outcome::default();
// In a presence context, we don't care about ext2 being equal to tags1
if ctx.mode.is_eq() {
let extend_ext_with_uninhabited = if ctx.mode.is_eq() {
// SPECIAL-CASE: if we can grow empty extensions with uninhabited types,
// patch `ext2` to grow accordingly.
if should_extend_ext_with_uninhabited_type(env.subs, ext2, extra_tags_in_1) {
let extend_ext_with_uninhabited =
should_extend_ext_with_uninhabited_type(env.subs, ext2, extra_tags_in_1);
if extend_ext_with_uninhabited {
let new_ext = fresh(env, pool, ctx, Content::FlexVar(None));
let new_union = Structure(FlatType::TagUnion(tags2, new_ext));
let mut new_desc = ctx.second_desc;
@ -2348,7 +2377,11 @@ fn unify_tag_unions<M: MetaCollector>(
return ext_outcome;
}
total_outcome.union(ext_outcome);
}
extend_ext_with_uninhabited
} else {
false
};
let shared_tags_outcome = unify_shared_tags_new(
env,
@ -2360,6 +2393,11 @@ fn unify_tag_unions<M: MetaCollector>(
recursion_var,
);
total_outcome.union(shared_tags_outcome);
if extend_ext_with_uninhabited {
close_uninhabited_extended_union(env.subs, ctx.first);
}
total_outcome
} else {
let other_tags = OtherTags2::Union(separate.only_in_1.clone(), separate.only_in_2.clone());