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fix: relaxing occur checks

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This commit is contained in:
Shunsuke Shibayama 2023-10-01 11:53:29 +09:00
parent c985fcb4d8
commit 162581611d
3 changed files with 21 additions and 0 deletions
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10
crates/erg_compiler/context/unify.rs
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@ -53,6 +53,8 @@ impl<'c, 'l, 'u, L: Locational> Unifier<'c, 'l, 'u, L> {
impl<'c, 'l, 'u, L: Locational> Unifier<'c, 'l, 'u, L> {
/// ```erg
/// occur(?T, ?T) ==> OK
/// occur(?T(<: ?U), ?U) ==> OK
/// occur(?T, ?U(:> ?T)) ==> OK
/// occur(X -> ?T, ?T) ==> Error
/// occur(X -> ?T, X -> ?T) ==> OK
/// occur(?T, ?T -> X) ==> Error
@ -65,6 +67,14 @@ impl<'c, 'l, 'u, L: Locational> Unifier<'c, 'l, 'u, L> {
fn occur(&self, maybe_sub: &Type, maybe_sup: &Type) -> TyCheckResult<()> {
if maybe_sub == maybe_sup {
return Ok(());
} else if let Some(sup) = maybe_sub.get_super() {
if &sup == maybe_sup {
return Ok(());
}
} else if let Some(sub) = maybe_sup.get_sub() {
if &sub == maybe_sub {
return Ok(());
}
}
match (maybe_sub, maybe_sup) {
(FreeVar(fv), _) if fv.is_linked() => self.occur(&fv.crack(), maybe_sup),