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Rollup merge of #137102 - compiler-errors:name_regions2, r=oli-obk

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Rework `name_regions` to not rely on reverse scc graph for non-member-constrain usages

Fixes https://github.com/rust-lang/rust/issues/137015

Splits the `name_regions` into two versions: One meant for member region constraint error reporting (which I've renamed to `name_regions_for_member_constraint`), and one meant *just* to replace region vids with an external region.

Use the latter in the usage sites I added in #136559, since the regions returned by `name_regions_for_member_constraint` are also not *totally* accurate (which is fine for how they're used for member region constraint error reporting -- they're intentionally returning overapproximated universal regions so that we have something to name in `+ use<'a>` suggestions, because opaques can only capture universal regions and since member region constraints don't insert any edges into the region graph, the error region is probably gonna be shorter than a universal region) and because that function requires the reverse scc graph to have been computed which isn't done for our usages in #136559.
This commit is contained in:
Matthias Krüger 2025-02-16 17:14:05 +01:00 • committed by GitHub
commit ea9c8d9c17
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4 changed files with 58 additions and 7 deletions
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30
compiler/rustc_borrowck/src/diagnostics/region_errors.rs
View file

@ -14,7 +14,10 @@ use rustc_infer::infer::{NllRegionVariableOrigin, RelateParamBound};
use rustc_middle::bug;
use rustc_middle::hir::place::PlaceBase;
use rustc_middle::mir::{AnnotationSource, ConstraintCategory, ReturnConstraint};
use rustc_middle::ty::{self, GenericArgs, Region, RegionVid, Ty, TyCtxt, TypeVisitor};
use rustc_middle::ty::fold::fold_regions;
use rustc_middle::ty::{
self, GenericArgs, Region, RegionVid, Ty, TyCtxt, TypeFoldable, TypeVisitor,
};
use rustc_span::{Ident, Span, kw};
use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
use rustc_trait_selection::error_reporting::infer::nice_region_error::{
@ -183,6 +186,17 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
}
}
/// Map the regions in the type to named regions, where possible.
fn name_regions<T>(&self, tcx: TyCtxt<'tcx>, ty: T) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
fold_regions(tcx, ty, |region, _| match *region {
ty::ReVar(vid) => self.to_error_region(vid).unwrap_or(region),
_ => region,
})
}
/// Returns `true` if a closure is inferred to be an `FnMut` closure.
fn is_closure_fn_mut(&self, fr: RegionVid) -> bool {
if let Some(ty::ReLateParam(late_param)) = self.to_error_region(fr).as_deref()
@ -314,7 +328,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
let type_test_span = type_test.span;
if let Some(lower_bound_region) = lower_bound_region {
let generic_ty = self.regioncx.name_regions(
let generic_ty = self.name_regions(
self.infcx.tcx,
type_test.generic_kind.to_ty(self.infcx.tcx),
);
@ -323,7 +337,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
self.body.source.def_id().expect_local(),
type_test_span,
Some(origin),
self.regioncx.name_regions(self.infcx.tcx, type_test.generic_kind),
self.name_regions(self.infcx.tcx, type_test.generic_kind),
lower_bound_region,
));
} else {
@ -354,9 +368,13 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
}
RegionErrorKind::UnexpectedHiddenRegion { span, hidden_ty, key, member_region } => {
let named_ty = self.regioncx.name_regions(self.infcx.tcx, hidden_ty);
let named_key = self.regioncx.name_regions(self.infcx.tcx, key);
let named_region = self.regioncx.name_regions(self.infcx.tcx, member_region);
let named_ty =
self.regioncx.name_regions_for_member_constraint(self.infcx.tcx, hidden_ty);
let named_key =
self.regioncx.name_regions_for_member_constraint(self.infcx.tcx, key);
let named_region = self
.regioncx
.name_regions_for_member_constraint(self.infcx.tcx, member_region);
let diag = unexpected_hidden_region_diagnostic(
self.infcx,
self.mir_def_id(),

8
compiler/rustc_borrowck/src/region_infer/opaque_types.rs
View file

@ -204,7 +204,13 @@ impl<'tcx> RegionInferenceContext<'tcx> {
/// that the regions produced are in fact equal to the named region they are
/// replaced with. This is fine because this function is only to improve the
/// region names in error messages.
pub(crate) fn name_regions<T>(&self, tcx: TyCtxt<'tcx>, ty: T) -> T
///
/// This differs from `MirBorrowckCtxt::name_regions` since it is particularly
/// lax with mapping region vids that are *shorter* than a universal region to
/// that universal region. This is useful for member region constraints since
/// we want to suggest a universal region name to capture even if it's technically
/// not equal to the error region.
pub(crate) fn name_regions_for_member_constraint<T>(&self, tcx: TyCtxt<'tcx>, ty: T) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{

13
tests/ui/borrowck/alias-liveness/name-region.rs Normal file
View file

@ -0,0 +1,13 @@
// Make sure we don't ICE when trying to name the regions that appear in the alias
// of the type test error.
trait AnotherTrait {
type Ty2<'a>;
}
fn test_alias<T: AnotherTrait>(_: &'static T::Ty2<'_>) {
let _: &'static T::Ty2<'_>;
//~^ ERROR the associated type `<T as AnotherTrait>::Ty2<'_>` may not live long enough
}
fn main() {}

14
tests/ui/borrowck/alias-liveness/name-region.stderr Normal file
View file

@ -0,0 +1,14 @@
error[E0310]: the associated type `<T as AnotherTrait>::Ty2<'_>` may not live long enough
--> $DIR/name-region.rs:9:12
|
LL | let _: &'static T::Ty2<'_>;
| ^^^^^^^^^^^^^^^^^^^
| |
| the associated type `<T as AnotherTrait>::Ty2<'_>` must be valid for the static lifetime...
| ...so that the type `<T as AnotherTrait>::Ty2<'_>` will meet its required lifetime bounds
|
= help: consider adding an explicit lifetime bound `<T as AnotherTrait>::Ty2<'_>: 'static`...
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0310`.