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.
diff --git a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
index aa968a1..7c9e916 100644
--- a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
@@ -49,7 +49,7 @@ pub(crate) fn relate(expected: Ty<'tcx>, found: Ty<'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 @@ pub(crate) fn report_error(
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 @@ fn nice_error<'infcx>(
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 @@ fn report_error(
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) {
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 6b11f1a..b2056cc 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -404,7 +404,7 @@ pub(crate) fn report_region_errors(&mut self, nll_errors: RegionErrors<'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 } => {
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index a80d74d..eebce11 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -1623,30 +1623,23 @@ fn check_bound_universal_region(
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))]
@@ -2066,7 +2059,7 @@ pub(crate) fn best_blame_constraint(
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,
@@ -2118,9 +2111,13 @@ pub(crate) fn best_blame_constraint(
// 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 {
diff --git a/compiler/rustc_borrowck/src/region_infer/values.rs b/compiler/rustc_borrowck/src/region_infer/values.rs
index d9ac5b5..f142721 100644
--- a/compiler/rustc_borrowck/src/region_infer/values.rs
+++ b/compiler/rustc_borrowck/src/region_infer/values.rs
@@ -21,7 +21,7 @@ pub(crate) struct PlaceholderIndex {}
/// 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),
