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Better errors for implied static bound

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This commit is contained in:
Jack Huey 2022-08-23 01:13:07 -04:00
parent ff623ffc39
commit c75817b0a7
23 changed files with 345 additions and 99 deletions
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30
compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
View file

@ -15,7 +15,7 @@ use rustc_middle::ty::{self, RegionVid, TyCtxt};
use rustc_span::symbol::{kw, Symbol};
use rustc_span::{sym, DesugaringKind, Span};
use crate::region_infer::BlameConstraint;
use crate::region_infer::{BlameConstraint, ExtraConstraintInfo};
use crate::{
borrow_set::BorrowData, nll::ConstraintDescription, region_infer::Cause, MirBorrowckCtxt,
WriteKind,
@ -38,6 +38,7 @@ pub(crate) enum BorrowExplanation<'tcx> {
span: Span,
region_name: RegionName,
opt_place_desc: Option<String>,
extra_info: Vec<ExtraConstraintInfo>,
},
Unexplained,
}
@ -243,6 +244,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
ref region_name,
ref opt_place_desc,
from_closure: _,
ref extra_info,
} => {
region_name.highlight_region_name(err);
@ -268,6 +270,14 @@ impl<'tcx> BorrowExplanation<'tcx> {
);
};
for extra in extra_info {
match extra {
ExtraConstraintInfo::PlaceholderFromPredicate(span) => {
err.span_note(*span, format!("due to current limitations in the borrow checker, this implies a `'static` lifetime"));
}
}
}
self.add_lifetime_bound_suggestion_to_diagnostic(err, &category, span, region_name);
}
_ => {}
@ -309,16 +319,17 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
&self,
borrow_region: RegionVid,
outlived_region: RegionVid,
) -> (ConstraintCategory<'tcx>, bool, Span, Option<RegionName>) {
let BlameConstraint { category, from_closure, cause, variance_info: _ } = self
.regioncx
.best_blame_constraint(borrow_region, NllRegionVariableOrigin::FreeRegion, |r| {
self.regioncx.provides_universal_region(r, borrow_region, outlived_region)
});
) -> (ConstraintCategory<'tcx>, bool, Span, Option<RegionName>, Vec<ExtraConstraintInfo>) {
let (blame_constraint, extra_info) = self.regioncx.best_blame_constraint(
borrow_region,
NllRegionVariableOrigin::FreeRegion,
|r| self.regioncx.provides_universal_region(r, borrow_region, outlived_region),
);
let BlameConstraint { category, from_closure, cause, .. } = blame_constraint;
let outlived_fr_name = self.give_region_a_name(outlived_region);
(category, from_closure, cause.span, outlived_fr_name)
(category, from_closure, cause.span, outlived_fr_name, extra_info)
}
/// Returns structured explanation for *why* the borrow contains the
@ -390,7 +401,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
None => {
if let Some(region) = self.to_error_region_vid(borrow_region_vid) {
let (category, from_closure, span, region_name) =
let (category, from_closure, span, region_name, extra_info) =
self.free_region_constraint_info(borrow_region_vid, region);
if let Some(region_name) = region_name {
let opt_place_desc = self.describe_place(borrow.borrowed_place.as_ref());
@ -400,6 +411,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
span,
region_name,
opt_place_desc,
extra_info,
}
} else {
debug!("Could not generate a region name");

8
compiler/rustc_borrowck/src/diagnostics/region_errors.rs
View file

@ -354,10 +354,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
) {
debug!("report_region_error(fr={:?}, outlived_fr={:?})", fr, outlived_fr);
let BlameConstraint { category, cause, variance_info, from_closure: _ } =
self.regioncx.best_blame_constraint(fr, fr_origin, |r| {
let BlameConstraint { category, cause, variance_info, .. } = self
.regioncx
.best_blame_constraint(fr, fr_origin, |r| {
self.regioncx.provides_universal_region(r, fr, outlived_fr)
});
})
.0;
debug!("report_region_error: category={:?} {:?} {:?}", category, cause, variance_info);

49
compiler/rustc_borrowck/src/region_infer/mod.rs
View file

@ -245,6 +245,11 @@ enum Trace<'tcx> {
NotVisited,
}
#[derive(Clone, PartialEq, Eq, Debug)]
pub enum ExtraConstraintInfo {
PlaceholderFromPredicate(Span),
}
impl<'tcx> RegionInferenceContext<'tcx> {
/// Creates a new region inference context with a total of
/// `num_region_variables` valid inference variables; the first N
@ -1818,10 +1823,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
fr1_origin: NllRegionVariableOrigin,
fr2: RegionVid,
) -> (ConstraintCategory<'tcx>, ObligationCause<'tcx>) {
let BlameConstraint { category, cause, .. } =
self.best_blame_constraint(fr1, fr1_origin, |r| {
self.provides_universal_region(r, fr1, fr2)
});
let BlameConstraint { category, cause, .. } = self
.best_blame_constraint(fr1, fr1_origin, |r| self.provides_universal_region(r, fr1, fr2))
.0;
(category, cause)
}
@ -2010,7 +2014,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
from_region: RegionVid,
from_region_origin: NllRegionVariableOrigin,
target_test: impl Fn(RegionVid) -> bool,
) -> BlameConstraint<'tcx> {
) -> (BlameConstraint<'tcx>, Vec<ExtraConstraintInfo>) {
// Find all paths
let (path, target_region) =
self.find_constraint_paths_between_regions(from_region, target_test).unwrap();
@ -2026,6 +2030,18 @@ impl<'tcx> RegionInferenceContext<'tcx> {
.collect::<Vec<_>>()
);
let mut extra_info = vec![];
for constraint in path.iter() {
let outlived = constraint.sub;
let Some(origin) = self.var_infos.get(outlived) else { continue; };
let RegionVariableOrigin::Nll(NllRegionVariableOrigin::Placeholder(p)) = origin.origin else { continue; };
debug!(?constraint, ?p);
let ConstraintCategory::Predicate(span) = constraint.category else { continue; };
extra_info.push(ExtraConstraintInfo::PlaceholderFromPredicate(span));
// We only want to point to one
break;
}
// We try to avoid reporting a `ConstraintCategory::Predicate` as our best constraint.
// Instead, we use it to produce an improved `ObligationCauseCode`.
// FIXME - determine what we should do if we encounter multiple `ConstraintCategory::Predicate`
@ -2073,6 +2089,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
from_closure,
cause: ObligationCause::new(span, CRATE_HIR_ID, cause_code),
variance_info: constraint.variance_info,
outlives_constraint: *constraint,
}
})
.collect();
@ -2174,7 +2191,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
let best_choice =
if blame_source { range.rev().find(find_region) } else { range.find(find_region) };
debug!(?best_choice, ?blame_source);
debug!(?best_choice, ?blame_source, ?extra_info);
if let Some(i) = best_choice {
if let Some(next) = categorized_path.get(i + 1) {
@ -2183,7 +2200,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
{
// The return expression is being influenced by the return type being
// impl Trait, point at the return type and not the return expr.
return next.clone();
return (next.clone(), extra_info);
}
}
@ -2203,7 +2220,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
}
}
return categorized_path[i].clone();
return (categorized_path[i].clone(), extra_info);
}
// If that search fails, that is.. unusual. Maybe everything
@ -2213,7 +2230,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
categorized_path.sort_by(|p0, p1| p0.category.cmp(&p1.category));
debug!("sorted_path={:#?}", categorized_path);
categorized_path.remove(0)
(categorized_path.remove(0), extra_info)
}
pub(crate) fn universe_info(&self, universe: ty::UniverseIndex) -> UniverseInfo<'tcx> {
@ -2295,7 +2312,13 @@ impl<'tcx> ClosureRegionRequirementsExt<'tcx> for ClosureRegionRequirements<'tcx
outlives_requirement={:?}",
region, outlived_region, outlives_requirement,
);
ty::Binder::dummy(ty::OutlivesPredicate(region.into(), outlived_region))
(
ty::Binder::dummy(ty::OutlivesPredicate(
region.into(),
outlived_region,
)),
ConstraintCategory::BoringNoLocation,
)
}
ClosureOutlivesSubject::Ty(ty) => {
@ -2305,7 +2328,10 @@ impl<'tcx> ClosureRegionRequirementsExt<'tcx> for ClosureRegionRequirements<'tcx
outlives_requirement={:?}",
ty, outlived_region, outlives_requirement,
);
ty::Binder::dummy(ty::OutlivesPredicate(ty.into(), outlived_region))
(
ty::Binder::dummy(ty::OutlivesPredicate(ty.into(), outlived_region)),
ConstraintCategory::BoringNoLocation,
)
}
}
})
@ -2319,4 +2345,5 @@ pub struct BlameConstraint<'tcx> {
pub from_closure: bool,
pub cause: ObligationCause<'tcx>,
pub variance_info: ty::VarianceDiagInfo<'tcx>,
pub outlives_constraint: OutlivesConstraint<'tcx>,
}

4
compiler/rustc_borrowck/src/type_check/canonical.rs
View file

@ -25,7 +25,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
/// constraints should occur within this method so that those
/// constraints can be properly localized!**
#[instrument(skip(self, op), level = "trace")]
pub(super) fn fully_perform_op<R, Op>(
pub(super) fn fully_perform_op<R: fmt::Debug, Op>(
&mut self,
locations: Locations,
category: ConstraintCategory<'tcx>,
@ -39,6 +39,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
let TypeOpOutput { output, constraints, error_info } = op.fully_perform(self.infcx)?;
debug!(?output, ?constraints);
if let Some(data) = constraints {
self.push_region_constraints(locations, category, data);
}

31
compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
View file

@ -86,7 +86,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
}
}
pub(super) fn convert(&mut self, query_constraint: &QueryOutlivesConstraint<'tcx>) {
fn convert(&mut self, query_constraint: &QueryOutlivesConstraint<'tcx>) {
debug!("generate: constraints at: {:#?}", self.locations);
// Extract out various useful fields we'll need below.
@ -98,15 +98,18 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
// region constraints like `for<'a> 'a: 'b`. At some point
// when we move to universes, we will, and this assertion
// will start to fail.
let ty::OutlivesPredicate(k1, r2) = query_constraint.no_bound_vars().unwrap_or_else(|| {
bug!("query_constraint {:?} contained bound vars", query_constraint,);
});
let ty::OutlivesPredicate(k1, r2) =
query_constraint.0.no_bound_vars().unwrap_or_else(|| {
bug!("query_constraint {:?} contained bound vars", query_constraint,);
});
let constraint_category = query_constraint.1;
match k1.unpack() {
GenericArgKind::Lifetime(r1) => {
let r1_vid = self.to_region_vid(r1);
let r2_vid = self.to_region_vid(r2);
self.add_outlives(r1_vid, r2_vid);
self.add_outlives(r1_vid, r2_vid, constraint_category);
}
GenericArgKind::Type(t1) => {
@ -121,7 +124,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
Some(implicit_region_bound),
param_env,
)
.type_must_outlive(origin, t1, r2);
.type_must_outlive(origin, t1, r2, constraint_category);
}
GenericArgKind::Const(_) => {
@ -168,10 +171,19 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
}
}
fn add_outlives(&mut self, sup: ty::RegionVid, sub: ty::RegionVid) {
fn add_outlives(
&mut self,
sup: ty::RegionVid,
sub: ty::RegionVid,
category: ConstraintCategory<'tcx>,
) {
let category = match self.category {
ConstraintCategory::Boring | ConstraintCategory::BoringNoLocation => category,
_ => self.category,
};
self.constraints.outlives_constraints.push(OutlivesConstraint {
locations: self.locations,
category: self.category,
category,
span: self.span,
sub,
sup,
@ -191,10 +203,11 @@ impl<'a, 'b, 'tcx> TypeOutlivesDelegate<'tcx> for &'a mut ConstraintConversion<'
_origin: SubregionOrigin<'tcx>,
a: ty::Region<'tcx>,
b: ty::Region<'tcx>,
constraint_category: ConstraintCategory<'tcx>,
) {
let b = self.to_region_vid(b);
let a = self.to_region_vid(a);
self.add_outlives(b, a);
self.add_outlives(b, a, constraint_category);
}
fn push_verify(

2
compiler/rustc_borrowck/src/type_check/mod.rs
View file

@ -2560,7 +2560,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
.enumerate()
.filter_map(|(idx, constraint)| {
let ty::OutlivesPredicate(k1, r2) =
constraint.no_bound_vars().unwrap_or_else(|| {
constraint.0.no_bound_vars().unwrap_or_else(|| {
bug!("query_constraint {:?} contained bound vars", constraint,);
});