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Fix bug in closing heuristic

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Ayaz Hafiz 2022-10-25 17:19:16 -05:00
parent 7b9ce492c3
commit bb1f4cd5e8
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1 changed files with 17 additions and 2 deletions
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19
crates/compiler/solve/src/solve.rs
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@ -1866,6 +1866,12 @@ fn open_tag_union(subs: &mut Subs, var: Variable) {
} }
} }
/// Optimistically closes the positive type of a value matched in a `when` statement, to produce
/// better exhaustiveness error messages.
///
/// This should only be applied if it's already known that a `when` expression is not exhaustive.
///
/// See [Constraint::Exhaustive].
fn close_pattern_matched_tag_unions(subs: &mut Subs, var: Variable) { fn close_pattern_matched_tag_unions(subs: &mut Subs, var: Variable) {
let mut stack = vec![var]; let mut stack = vec![var];
while let Some(var) = stack.pop() { while let Some(var) = stack.pop() {
@ -1884,11 +1890,20 @@ fn close_pattern_matched_tag_unions(subs: &mut Subs, var: Variable) {
subs.set_content_unchecked(ext, Structure(FlatType::EmptyTagUnion)); subs.set_content_unchecked(ext, Structure(FlatType::EmptyTagUnion));
break; break;
} }
RigidVar(..) | RigidAbleVar(..) => {
// Don't touch rigids, they tell us more information than the heuristic
// of closing tag unions does for better exhaustiveness checking does.
break;
}
Structure(FlatType::TagUnion(_, deep_ext)) Structure(FlatType::TagUnion(_, deep_ext))
| Structure(FlatType::RecursiveTagUnion(_, _, deep_ext)) => { | Structure(FlatType::RecursiveTagUnion(_, _, deep_ext))
| Structure(FlatType::FunctionOrTagUnion(_, _, deep_ext)) => {
ext = *deep_ext; ext = *deep_ext;
} }
_ => internal_error!("not a tag union"), other => internal_error!(
"not a tag union: {:?}",
roc_types::subs::SubsFmtContent(other, subs)
),
} }
} }