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Rollup merge of #140257 - amandasystems:housecleaning, r=wesleywiser

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Some drive-by housecleaning in `rustc_borrowck`

This commit picks up a few odd ends discovered during the work on #130227. It adds some documentation and renames a few methods with too generic names to describe what they actually do. It also adds some debug output that was helpful during bug hunting and generally cleans up a few things (for my values of "clean").

r? lcnr
This commit is contained in:
Matthias Krüger 2025-04-25 07:50:27 +02:00 • committed by GitHub
commit e534fad2e5
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4 changed files with 39 additions and 45 deletions
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39
compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
View file

@ -49,7 +49,7 @@ impl<'tcx> UniverseInfo<'tcx> {
UniverseInfo::RelateTys { expected, found }
}
pub(crate) fn report_error(
pub(crate) fn report_erroneous_element(
&self,
mbcx: &mut MirBorrowckCtxt<'_, '_, 'tcx>,
placeholder: ty::PlaceholderRegion,
@ -68,7 +68,7 @@ impl<'tcx> UniverseInfo<'tcx> {
mbcx.buffer_error(err);
}
UniverseInfo::TypeOp(ref type_op_info) => {
type_op_info.report_error(mbcx, placeholder, error_element, cause);
type_op_info.report_erroneous_element(mbcx, placeholder, error_element, cause);
}
UniverseInfo::Other => {
// FIXME: This error message isn't great, but it doesn't show
@ -145,8 +145,11 @@ pub(crate) trait TypeOpInfo<'tcx> {
error_region: Option<ty::Region<'tcx>>,
) -> Option<Diag<'infcx>>;
/// Constraints require that `error_element` appear in the
/// values of `placeholder`, but this cannot be proven to
/// hold. Report an error.
#[instrument(level = "debug", skip(self, mbcx))]
fn report_error(
fn report_erroneous_element(
&self,
mbcx: &mut MirBorrowckCtxt<'_, '_, 'tcx>,
placeholder: ty::PlaceholderRegion,
@ -190,12 +193,7 @@ pub(crate) trait TypeOpInfo<'tcx> {
let nice_error = self.nice_error(mbcx, cause, placeholder_region, error_region);
debug!(?nice_error);
if let Some(nice_error) = nice_error {
mbcx.buffer_error(nice_error);
} else {
mbcx.buffer_error(self.fallback_error(tcx, span));
}
mbcx.buffer_error(nice_error.unwrap_or_else(|| self.fallback_error(tcx, span)));
}
}
@ -450,7 +448,8 @@ fn try_extract_error_from_region_constraints<'a, 'tcx>(
ty::ReVar(vid) => universe_of_region(vid),
_ => ty::UniverseIndex::ROOT,
};
let matches =
// Are the two regions the same?
let regions_the_same =
|a_region: Region<'tcx>, b_region: Region<'tcx>| match (a_region.kind(), b_region.kind()) {
(RePlaceholder(a_p), RePlaceholder(b_p)) => a_p.bound == b_p.bound,
_ => a_region == b_region,
@ -459,7 +458,7 @@ fn try_extract_error_from_region_constraints<'a, 'tcx>(
|constraint: &Constraint<'tcx>, cause: &SubregionOrigin<'tcx>, exact| match *constraint {
Constraint::RegSubReg(sub, sup)
if ((exact && sup == placeholder_region)
|| (!exact && matches(sup, placeholder_region)))
|| (!exact && regions_the_same(sup, placeholder_region)))
&& sup != sub =>
{
Some((sub, cause.clone()))
@ -468,23 +467,21 @@ fn try_extract_error_from_region_constraints<'a, 'tcx>(
if (exact
&& sup == placeholder_region
&& !universe_of_region(vid).can_name(placeholder_universe))
|| (!exact && matches(sup, placeholder_region)) =>
|| (!exact && regions_the_same(sup, placeholder_region)) =>
{
Some((ty::Region::new_var(infcx.tcx, vid), cause.clone()))
}
_ => None,
};
let mut info = region_constraints
.constraints
.iter()
.find_map(|(constraint, cause)| check(constraint, cause, true));
if info.is_none() {
info = region_constraints
let mut find_culprit = |exact_match: bool| {
region_constraints
.constraints
.iter()
.find_map(|(constraint, cause)| check(constraint, cause, false));
}
let (sub_region, cause) = info?;
.find_map(|(constraint, cause)| check(constraint, cause, exact_match))
};
let (sub_region, cause) = find_culprit(true).or_else(|| find_culprit(false))?;
debug!(?sub_region, "cause = {:#?}", cause);
let error = match (error_region, sub_region.kind()) {

2
compiler/rustc_borrowck/src/diagnostics/region_errors.rs
View file

@ -405,7 +405,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
let universe = placeholder.universe;
let universe_info = self.regioncx.universe_info(universe);
universe_info.report_error(self, placeholder, error_element, cause);
universe_info.report_erroneous_element(self, placeholder, error_element, cause);
}
RegionErrorKind::RegionError { fr_origin, longer_fr, shorter_fr, is_reported } => {

41
compiler/rustc_borrowck/src/region_infer/mod.rs
View file

@ -1628,30 +1628,23 @@ impl<'tcx> RegionInferenceContext<'tcx> {
let longer_fr_scc = self.constraint_sccs.scc(longer_fr);
debug!("check_bound_universal_region: longer_fr_scc={:?}", longer_fr_scc,);
for error_element in self.scc_values.elements_contained_in(longer_fr_scc) {
match error_element {
RegionElement::Location(_) | RegionElement::RootUniversalRegion(_) => {}
// If we have some bound universal region `'a`, then the only
// elements it can contain is itself -- we don't know anything
// else about it!
RegionElement::PlaceholderRegion(placeholder1) => {
if placeholder == placeholder1 {
continue;
}
}
}
// If we have some bound universal region `'a`, then the only
// elements it can contain is itself -- we don't know anything
// else about it!
if let Some(error_element) = self
.scc_values
.elements_contained_in(longer_fr_scc)
.find(|e| *e != RegionElement::PlaceholderRegion(placeholder))
{
// Stop after the first error, it gets too noisy otherwise, and does not provide more information.
errors_buffer.push(RegionErrorKind::BoundUniversalRegionError {
longer_fr,
error_element,
placeholder,
});
// Stop after the first error, it gets too noisy otherwise, and does not provide more
// information.
break;
} else {
debug!("check_bound_universal_region: all bounds satisfied");
}
debug!("check_bound_universal_region: all bounds satisfied");
}
#[instrument(level = "debug", skip(self, infcx, errors_buffer))]
@ -2071,7 +2064,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
constraint.category
};
match category {
let interest = match category {
// Returns usually provide a type to blame and have specially written diagnostics,
// so prioritize them.
ConstraintCategory::Return(_) => 0,
@ -2123,9 +2116,13 @@ impl<'tcx> RegionInferenceContext<'tcx> {
// specific, and are not used for relations that would make sense to blame.
ConstraintCategory::BoringNoLocation => 6,
// Do not blame internal constraints.
ConstraintCategory::Internal => 7,
ConstraintCategory::IllegalUniverse => 8,
}
ConstraintCategory::IllegalUniverse => 7,
ConstraintCategory::Internal => 8,
};
debug!("constraint {constraint:?} category: {category:?}, interest: {interest:?}");
interest
};
let best_choice = if blame_source {

2
compiler/rustc_borrowck/src/region_infer/values.rs
View file

@ -21,7 +21,7 @@ rustc_index::newtype_index! {
/// An individual element in a region value -- the value of a
/// particular region variable consists of a set of these elements.
#[derive(Debug, Clone)]
#[derive(Debug, Clone, PartialEq)]
pub(crate) enum RegionElement {
/// A point in the control-flow graph.
Location(Location),