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Implement overflow for infinite implied lifetime bounds #138676

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Implement overflow for infinite implied lifetime bounds #138676

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29 changes: 25 additions & 4 deletions compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,8 +24,8 @@ pub(super) fn infer_predicates(

// If new predicates were added then we need to re-calculate
// all crates since there could be new implied predicates.
loop {
let mut predicates_added = false;
for i in 0.. {
let mut predicates_added: Option<Vec<_>> = None;
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just use a Vec with .is_empty()?

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🤔 tru


// Visit all the crates and infer predicates
for id in tcx.hir_free_items() {
Expand Down Expand Up @@ -83,13 +83,34 @@ pub(super) fn infer_predicates(
.get(&item_did.to_def_id())
.map_or(0, |p| p.as_ref().skip_binder().len());
if item_required_predicates.len() > item_predicates_len {
predicates_added = true;
predicates_added.get_or_insert_default().push(item_did);
global_inferred_outlives
.insert(item_did.to_def_id(), ty::EarlyBinder::bind(item_required_predicates));
}
}

if !predicates_added {
if let Some(ids) = predicates_added {
if !tcx.recursion_limit().value_within_limit(i) {
let msg = if let &[id] = &ids[..] {
format!(
"overflow computing implied lifetime bounds for `{}`",
tcx.def_path_str(id),
)
} else {
"overflow computing implied lifetime bounds".to_string()
};
tcx.dcx()
.struct_span_err(
ids.iter().map(|id| tcx.def_span(*id)).collect::<Vec<_>>(),
msg,
)
.emit();
for id in ids {
global_inferred_outlives.shift_remove(&id.to_def_id());
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that seems suboptimal 🤔 what happens if u don't remove the added implied bounds here?

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hangs in both the old and need solvers due to RECURSION_LIMIT deep types having to be normalized

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ill put a comment but it's necessary im p sure

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makes sense, we get very deep assoc items. I feel like we can also have cycles of length 2 in which case we still get a hang as we don't remove the implied bounds for the other cycle participant? 🤔

vibes, but maybe just fatal error? 😁

}
break;
}
} else {
break;
}
}
Expand Down
11 changes: 11 additions & 0 deletions tests/ui/implied-bounds/overflow.rs
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@@ -0,0 +1,11 @@
trait Tailed<'a>: 'a {
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pls add doc comment/link to issue

type Tail: Tailed<'a>;
}

struct List<'a, T: Tailed<'a>> {
//~^ ERROR overflow computing implied lifetime bounds for `List`
next: Box<List<'a, T::Tail>>,
node: &'a T,
}

fn main() {}
8 changes: 8 additions & 0 deletions tests/ui/implied-bounds/overflow.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
error: overflow computing implied lifetime bounds for `List`
--> $DIR/overflow.rs:5:1
|
LL | struct List<'a, T: Tailed<'a>> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

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