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Admit occurs check under recursive tag unions when programs have type errors

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Ayaz Hafiz 2022-11-16 12:30:09 -06:00
parent 216a786d52
commit a8b55dc794
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GPG key ID: 0E2A37416A25EF58
2 changed files with 40 additions and 8 deletions
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19
crates/compiler/unify/src/unify.rs
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@ -1,6 +1,6 @@
use bitflags::bitflags;
use roc_collections::{VecMap, VecSet};
use roc_debug_flags::dbg_do;
use roc_debug_flags::{dbg_do, dbg_set, ROC_VERIFY_OCCURS_RECURSION};
#[cfg(debug_assertions)]
use roc_debug_flags::{ROC_PRINT_MISMATCHES, ROC_PRINT_UNIFICATIONS};
use roc_error_macros::internal_error;
@ -2615,7 +2615,22 @@ fn maybe_mark_union_recursive(env: &mut Env, union_var: Variable) {
}) {
return;
} else {
internal_error!("recursive loop does not contain a tag union")
// We may have partially solved a recursive type, but still see an occurs, if the type
// has errors inside of it. As such, admit this; however, for well-typed programs, this
// case should never be observed. Set ROC_VERIFY_OCCURS_RECURSION to verify this branch
// is not reached for well-typed programs.
if dbg_set!(ROC_VERIFY_OCCURS_RECURSION)
|| !chain.iter().any(|&var| {
matches!(
subs.get_content_without_compacting(var),
Content::Structure(FlatType::RecursiveTagUnion(..))
)
})
{
internal_error!("recursive loop does not contain a tag union")
}
return;
}
}
}