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Merge pull request #3600 from rtfeldman/i3298

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Various improvements to is-open constraints/catch-all branches in patterns
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Folkert de Vries 2022-07-23 12:49:35 +02:00 • committed by GitHub
commit 860df057dc
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7 changed files with 182 additions and 113 deletions
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32
crates/compiler/solve/src/solve.rs
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@ -1653,25 +1653,35 @@ fn open_tag_union(subs: &mut Subs, var: Variable) {
use {Content::*, FlatType::*};
let desc = subs.get(var);
if let Structure(TagUnion(tags, ext)) = desc.content {
if let Structure(EmptyTagUnion) = subs.get_content_without_compacting(ext) {
let new_ext = subs.fresh_unnamed_flex_var();
subs.set_rank(new_ext, desc.rank);
let new_union = Structure(TagUnion(tags, new_ext));
subs.set_content(var, new_union);
match desc.content {
Structure(TagUnion(tags, ext)) => {
if let Structure(EmptyTagUnion) = subs.get_content_without_compacting(ext) {
let new_ext = subs.fresh_unnamed_flex_var();
subs.set_rank(new_ext, desc.rank);
let new_union = Structure(TagUnion(tags, new_ext));
subs.set_content(var, new_union);
}
// Also open up all nested tag unions.
let all_vars = tags.variables().into_iter();
stack.extend(all_vars.flat_map(|slice| subs[slice]).map(|var| subs[var]));
}
// Also open up all nested tag unions.
let all_vars = tags.variables().into_iter();
stack.extend(all_vars.flat_map(|slice| subs[slice]).map(|var| subs[var]));
Structure(Record(fields, _)) => {
// Open up all nested tag unions.
stack.extend(subs.get_subs_slice(fields.variables()));
}
_ => {
// Everything else is not a structural type that can be opened
// (i.e. cannot be matched in a pattern-match)
}
}
// Today, an "open" constraint doesn't affect any types
// other than tag unions. Recursive tag unions are constructed
// at a later time (during occurs checks after tag unions are
// resolved), so that's not handled here either.
// NB: Handle record types here if we add presence constraints
// to their type inference as well.
}
}