Revert "Better errors for implied static bound"

This reverts commit c75817b0a75d4b6b01ee10900ba5d01d4915e6a8.

6 files changed, 34 insertions, 90 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 1c01e78abd4..3b58da11e84 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -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, ExtraConstraintInfo};
+use crate::region_infer::BlameConstraint;
 use crate::{
     borrow_set::BorrowData, nll::ConstraintDescription, region_infer::Cause, MirBorrowckCtxt,
     WriteKind,
@@ -38,7 +38,6 @@ pub(crate) enum BorrowExplanation<'tcx> {
         span: Span,
         region_name: RegionName,
         opt_place_desc: Option<String>,
-        extra_info: Vec<ExtraConstraintInfo>,
     },
     Unexplained,
 }
@@ -244,7 +243,6 @@ impl<'tcx> BorrowExplanation<'tcx> {
                 ref region_name,
                 ref opt_place_desc,
                 from_closure: _,
-                ref extra_info,
             } => {
                 region_name.highlight_region_name(err);
 
@@ -270,14 +268,6 @@ 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);
             }
             _ => {}
@@ -319,17 +309,16 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         &self,
         borrow_region: RegionVid,
         outlived_region: RegionVid,
-    ) -> (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;
+    ) -> (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)
+            });
 
         let outlived_fr_name = self.give_region_a_name(outlived_region);
 
-        (category, from_closure, cause.span, outlived_fr_name, extra_info)
+        (category, from_closure, cause.span, outlived_fr_name)
     }
 
     /// Returns structured explanation for *why* the borrow contains the
@@ -401,7 +390,7 @@ 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, extra_info) =
+                    let (category, from_closure, span, region_name) =
                         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());
@@ -411,7 +400,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             span,
                             region_name,
                             opt_place_desc,
-                            extra_info,
                         }
                     } else {
                         debug!("Could not generate a region name");
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index c276719c227..e7681222fc1 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -354,12 +354,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     ) {
         debug!("report_region_error(fr={:?}, outlived_fr={:?})", fr, outlived_fr);
 
-        let BlameConstraint { category, cause, variance_info, .. } = self
-            .regioncx
-            .best_blame_constraint(fr, fr_origin, |r| {
+        let BlameConstraint { category, cause, variance_info, from_closure: _ } =
+            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);
 
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 244e6e3422d..79a3a247c48 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -245,11 +245,6 @@ 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
@@ -1823,9 +1818,10 @@ 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))
-            .0;
+        let BlameConstraint { category, cause, .. } =
+            self.best_blame_constraint(fr1, fr1_origin, |r| {
+                self.provides_universal_region(r, fr1, fr2)
+            });
         (category, cause)
     }
 
@@ -2014,7 +2010,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         from_region: RegionVid,
         from_region_origin: NllRegionVariableOrigin,
         target_test: impl Fn(RegionVid) -> bool,
-    ) -> (BlameConstraint<'tcx>, Vec<ExtraConstraintInfo>) {
+    ) -> BlameConstraint<'tcx> {
         // Find all paths
         let (path, target_region) =
             self.find_constraint_paths_between_regions(from_region, target_test).unwrap();
@@ -2030,18 +2026,6 @@ 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`
@@ -2089,7 +2073,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                     from_closure,
                     cause: ObligationCause::new(span, CRATE_HIR_ID, cause_code),
                     variance_info: constraint.variance_info,
-                    outlives_constraint: *constraint,
                 }
             })
             .collect();
@@ -2191,7 +2174,7 @@ 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, ?extra_info);
+        debug!(?best_choice, ?blame_source);
 
         if let Some(i) = best_choice {
             if let Some(next) = categorized_path.get(i + 1) {
@@ -2200,7 +2183,7 @@ 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(), extra_info);
+                    return next.clone();
                 }
             }
 
@@ -2220,7 +2203,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 }
             }
 
-            return (categorized_path[i].clone(), extra_info);
+            return categorized_path[i].clone();
         }
 
         // If that search fails, that is.. unusual. Maybe everything
@@ -2230,7 +2213,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         categorized_path.sort_by(|p0, p1| p0.category.cmp(&p1.category));
         debug!("sorted_path={:#?}", categorized_path);
 
-        (categorized_path.remove(0), extra_info)
+        categorized_path.remove(0)
     }
 
     pub(crate) fn universe_info(&self, universe: ty::UniverseIndex) -> UniverseInfo<'tcx> {
@@ -2312,13 +2295,7 @@ impl<'tcx> ClosureRegionRequirementsExt<'tcx> for ClosureRegionRequirements<'tcx
                              outlives_requirement={:?}",
                             region, outlived_region, outlives_requirement,
                         );
-                        (
-                            ty::Binder::dummy(ty::OutlivesPredicate(
-                                region.into(),
-                                outlived_region,
-                            )),
-                            ConstraintCategory::BoringNoLocation,
-                        )
+                        ty::Binder::dummy(ty::OutlivesPredicate(region.into(), outlived_region))
                     }
 
                     ClosureOutlivesSubject::Ty(ty) => {
@@ -2328,10 +2305,7 @@ impl<'tcx> ClosureRegionRequirementsExt<'tcx> for ClosureRegionRequirements<'tcx
                              outlives_requirement={:?}",
                             ty, outlived_region, outlives_requirement,
                         );
-                        (
-                            ty::Binder::dummy(ty::OutlivesPredicate(ty.into(), outlived_region)),
-                            ConstraintCategory::BoringNoLocation,
-                        )
+                        ty::Binder::dummy(ty::OutlivesPredicate(ty.into(), outlived_region))
                     }
                 }
             })
@@ -2345,5 +2319,4 @@ pub struct BlameConstraint<'tcx> {
     pub from_closure: bool,
     pub cause: ObligationCause<'tcx>,
     pub variance_info: ty::VarianceDiagInfo<'tcx>,
-    pub outlives_constraint: OutlivesConstraint<'tcx>,
 }
diff --git a/compiler/rustc_borrowck/src/type_check/canonical.rs b/compiler/rustc_borrowck/src/type_check/canonical.rs
index 8a3972a12c5..29195b3922f 100644
--- a/compiler/rustc_borrowck/src/type_check/canonical.rs
+++ b/compiler/rustc_borrowck/src/type_check/canonical.rs
@@ -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: fmt::Debug, Op>(
+    pub(super) fn fully_perform_op<R, Op>(
         &mut self,
         locations: Locations,
         category: ConstraintCategory<'tcx>,
@@ -39,8 +39,6 @@ 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);
         }
diff --git a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
index 71eae0583cb..9fab7ad914a 100644
--- a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
+++ b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
@@ -86,7 +86,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
         }
     }
 
-    fn convert(&mut self, query_constraint: &QueryOutlivesConstraint<'tcx>) {
+    pub(super) fn convert(&mut self, query_constraint: &QueryOutlivesConstraint<'tcx>) {
         debug!("generate: constraints at: {:#?}", self.locations);
 
         // Extract out various useful fields we'll need below.
@@ -98,18 +98,15 @@ 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.0.no_bound_vars().unwrap_or_else(|| {
-                bug!("query_constraint {:?} contained bound vars", query_constraint,);
-            });
-
-        let constraint_category = query_constraint.1;
+        let ty::OutlivesPredicate(k1, r2) = query_constraint.no_bound_vars().unwrap_or_else(|| {
+            bug!("query_constraint {:?} contained bound vars", query_constraint,);
+        });
 
         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, constraint_category);
+                self.add_outlives(r1_vid, r2_vid);
             }
 
             GenericArgKind::Type(t1) => {
@@ -124,7 +121,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
                     Some(implicit_region_bound),
                     param_env,
                 )
-                .type_must_outlive(origin, t1, r2, constraint_category);
+                .type_must_outlive(origin, t1, r2);
             }
 
             GenericArgKind::Const(_) => {
@@ -171,19 +168,10 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
         }
     }
 
-    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,
-        };
+    fn add_outlives(&mut self, sup: ty::RegionVid, sub: ty::RegionVid) {
         self.constraints.outlives_constraints.push(OutlivesConstraint {
             locations: self.locations,
-            category,
+            category: self.category,
             span: self.span,
             sub,
             sup,
@@ -203,11 +191,10 @@ 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, constraint_category);
+        self.add_outlives(b, a);
     }
 
     fn push_verify(
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 5f714cf723b..d2a54df10b5 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -2591,7 +2591,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 .enumerate()
                 .filter_map(|(idx, constraint)| {
                     let ty::OutlivesPredicate(k1, r2) =
-                        constraint.0.no_bound_vars().unwrap_or_else(|| {
+                        constraint.no_bound_vars().unwrap_or_else(|| {
                             bug!("query_constraint {:?} contained bound vars", constraint,);
                         });