Revert "Auto merge of #133858 - dianne:better-blame-constraints-for-static, r=lcnr"

This reverts commit 6afee11, reversing
changes made to 9c87288.

Author: lqd

Cargo.lock

@@ -4115,6 +4115,7 @@ name = "rustc_middle"
 version = "0.0.0"
 dependencies = [
  "bitflags",
+ "derive-where",
  "either",
  "field-offset",
  "gsgdt",

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -1516,7 +1516,15 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         });
 
         self.explain_why_borrow_contains_point(location, borrow, None)
-            .add_explanation_to_diagnostic(&self, &mut err, "", Some(borrow_span), None);
+            .add_explanation_to_diagnostic(
+                self.infcx.tcx,
+                self.body,
+                &self.local_names,
+                &mut err,
+                "",
+                Some(borrow_span),
+                None,
+            );
         self.suggest_copy_for_type_in_cloned_ref(&mut err, place);
         let typeck_results = self.infcx.tcx.typeck(self.mir_def_id());
         if let Some(expr) = self.find_expr(borrow_span) {
@@ -1583,7 +1591,15 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         });
 
         self.explain_why_borrow_contains_point(location, borrow, None)
-            .add_explanation_to_diagnostic(&self, &mut err, "", None, None);
+            .add_explanation_to_diagnostic(
+                self.infcx.tcx,
+                self.body,
+                &self.local_names,
+                &mut err,
+                "",
+                None,
+                None,
+            );
         err
     }
 
@@ -1870,7 +1886,9 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         }
 
         explanation.add_explanation_to_diagnostic(
-            &self,
+            self.infcx.tcx,
+            self.body,
+            &self.local_names,
             &mut err,
             first_borrow_desc,
             None,
@@ -3028,7 +3046,15 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
 
             if let BorrowExplanation::MustBeValidFor { .. } = explanation {
             } else {
-                explanation.add_explanation_to_diagnostic(&self, &mut err, "", None, None);
+                explanation.add_explanation_to_diagnostic(
+                    self.infcx.tcx,
+                    self.body,
+                    &self.local_names,
+                    &mut err,
+                    "",
+                    None,
+                    None,
+                );
             }
         } else {
             err.span_label(borrow_span, "borrowed value does not live long enough");
@@ -3041,7 +3067,15 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 }
             });
 
-            explanation.add_explanation_to_diagnostic(&self, &mut err, "", Some(borrow_span), None);
+            explanation.add_explanation_to_diagnostic(
+                self.infcx.tcx,
+                self.body,
+                &self.local_names,
+                &mut err,
+                "",
+                Some(borrow_span),
+                None,
+            );
         }
 
         err
@@ -3094,7 +3128,15 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             _ => {}
         }
 
-        explanation.add_explanation_to_diagnostic(&self, &mut err, "", None, None);
+        explanation.add_explanation_to_diagnostic(
+            self.infcx.tcx,
+            self.body,
+            &self.local_names,
+            &mut err,
+            "",
+            None,
+            None,
+        );
 
         self.buffer_error(err);
     }
@@ -3267,7 +3309,15 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             }
             _ => {}
         }
-        explanation.add_explanation_to_diagnostic(&self, &mut err, "", None, None);
+        explanation.add_explanation_to_diagnostic(
+            self.infcx.tcx,
+            self.body,
+            &self.local_names,
+            &mut err,
+            "",
+            None,
+            None,
+        );
 
         borrow_spans.args_subdiag(&mut err, |args_span| {
             crate::session_diagnostics::CaptureArgLabel::Capture {
@@ -3758,8 +3808,15 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             }
         });
 
-        self.explain_why_borrow_contains_point(location, loan, None)
-            .add_explanation_to_diagnostic(&self, &mut err, "", None, None);
+        self.explain_why_borrow_contains_point(location, loan, None).add_explanation_to_diagnostic(
+            self.infcx.tcx,
+            self.body,
+            &self.local_names,
+            &mut err,
+            "",
+            None,
+            None,
+        );
 
         self.explain_deref_coercion(loan, &mut err);
 

compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs

@@ -8,6 +8,7 @@ use std::assert_matches::assert_matches;
 use rustc_errors::{Applicability, Diag};
 use rustc_hir as hir;
 use rustc_hir::intravisit::Visitor;
+use rustc_index::IndexSlice;
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault;
 use rustc_middle::mir::{
@@ -17,15 +18,14 @@ use rustc_middle::mir::{
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt};
 use rustc_middle::util::CallKind;
-use rustc_span::{DesugaringKind, Span, kw, sym};
+use rustc_span::{DesugaringKind, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::traits::FindExprBySpan;
 use tracing::{debug, instrument};
 
 use super::{RegionName, UseSpans, find_use};
 use crate::borrow_set::BorrowData;
-use crate::constraints::OutlivesConstraint;
 use crate::nll::ConstraintDescription;
-use crate::region_infer::{BlameConstraint, Cause};
+use crate::region_infer::{BlameConstraint, Cause, ExtraConstraintInfo};
 use crate::{MirBorrowckCtxt, WriteKind};
 
 #[derive(Debug)]
@@ -43,7 +43,7 @@ pub(crate) enum BorrowExplanation<'tcx> {
         span: Span,
         region_name: RegionName,
         opt_place_desc: Option<String>,
-        path: Vec<OutlivesConstraint<'tcx>>,
+        extra_info: Vec<ExtraConstraintInfo>,
     },
     Unexplained,
 }
@@ -63,16 +63,14 @@ impl<'tcx> BorrowExplanation<'tcx> {
     }
     pub(crate) fn add_explanation_to_diagnostic(
         &self,
-        cx: &MirBorrowckCtxt<'_, '_, 'tcx>,
+        tcx: TyCtxt<'tcx>,
+        body: &Body<'tcx>,
+        local_names: &IndexSlice<Local, Option<Symbol>>,
         err: &mut Diag<'_>,
         borrow_desc: &str,
         borrow_span: Option<Span>,
         multiple_borrow_span: Option<(Span, Span)>,
     ) {
-        let tcx = cx.infcx.tcx;
-        let body = cx.body;
-        let local_names = &cx.local_names;
-
         if let Some(span) = borrow_span {
             let def_id = body.source.def_id();
             if let Some(node) = tcx.hir().get_if_local(def_id)
@@ -308,7 +306,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
                 ref region_name,
                 ref opt_place_desc,
                 from_closure: _,
-                ref path,
+                ref extra_info,
             } => {
                 region_name.highlight_region_name(err);
 
@@ -330,8 +328,13 @@ impl<'tcx> BorrowExplanation<'tcx> {
                     );
                 };
 
-                cx.add_placeholder_from_predicate_note(err, &path);
-                cx.add_sized_or_copy_bound_info(err, category, &path);
+                for extra in extra_info {
+                    match extra {
+                        ExtraConstraintInfo::PlaceholderFromPredicate(span) => {
+                            err.span_note(*span, "due to current limitations in the borrow checker, this implies a `'static` lifetime");
+                        }
+                    }
+                }
 
                 if let ConstraintCategory::Cast {
                     is_implicit_coercion: true,
@@ -484,9 +487,8 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
         &self,
         borrow_region: RegionVid,
         outlived_region: RegionVid,
-    ) -> (ConstraintCategory<'tcx>, bool, Span, Option<RegionName>, Vec<OutlivesConstraint<'tcx>>)
-    {
-        let (blame_constraint, path) = self.regioncx.best_blame_constraint(
+    ) -> (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),
@@ -495,7 +497,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
 
         let outlived_fr_name = self.give_region_a_name(outlived_region);
 
-        (category, from_closure, cause.span, outlived_fr_name, path)
+        (category, from_closure, cause.span, outlived_fr_name, extra_info)
     }
 
     /// Returns structured explanation for *why* the borrow contains the
@@ -594,7 +596,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
 
             None => {
                 if let Some(region) = self.to_error_region_vid(borrow_region_vid) {
-                    let (category, from_closure, span, region_name, path) =
+                    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());
@@ -604,7 +606,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
                             span,
                             region_name,
                             opt_place_desc,
-                            path,
+                            extra_info,
                         }
                     } else {
                         debug!("Could not generate a region name");

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -8,16 +8,14 @@ use rustc_errors::{Applicability, Diag, MultiSpan};
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::{self as hir, CoroutineKind, LangItem};
 use rustc_index::IndexSlice;
-use rustc_infer::infer::{
-    BoundRegionConversionTime, NllRegionVariableOrigin, RegionVariableOrigin,
-};
+use rustc_infer::infer::BoundRegionConversionTime;
 use rustc_infer::traits::SelectionError;
 use rustc_middle::bug;
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::{
-    AggregateKind, CallSource, ConstOperand, ConstraintCategory, FakeReadCause, Local, LocalInfo,
-    LocalKind, Location, Operand, Place, PlaceRef, ProjectionElem, Rvalue, Statement,
-    StatementKind, Terminator, TerminatorKind,
+    AggregateKind, CallSource, ConstOperand, FakeReadCause, Local, LocalInfo, LocalKind, Location,
+    Operand, Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator,
+    TerminatorKind,
 };
 use rustc_middle::ty::print::Print;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
@@ -35,9 +33,7 @@ use tracing::debug;
 
 use super::MirBorrowckCtxt;
 use super::borrow_set::BorrowData;
-use crate::constraints::OutlivesConstraint;
 use crate::fluent_generated as fluent;
-use crate::nll::ConstraintDescription;
 use crate::session_diagnostics::{
     CaptureArgLabel, CaptureReasonLabel, CaptureReasonNote, CaptureReasonSuggest, CaptureVarCause,
     CaptureVarKind, CaptureVarPathUseCause, OnClosureNote,
@@ -623,52 +619,6 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         region.print(&mut printer).unwrap();
         printer.into_buffer()
     }
-
-    /// Add a note to region errors and borrow explanations when higher-ranked regions in predicates
-    /// implicitly introduce an "outlives `'static`" constraint.
-    fn add_placeholder_from_predicate_note(
-        &self,
-        err: &mut Diag<'_>,
-        path: &[OutlivesConstraint<'tcx>],
-    ) {
-        let predicate_span = path.iter().find_map(|constraint| {
-            let outlived = constraint.sub;
-            if let Some(origin) = self.regioncx.var_infos.get(outlived)
-                && let RegionVariableOrigin::Nll(NllRegionVariableOrigin::Placeholder(_)) =
-                    origin.origin
-                && let ConstraintCategory::Predicate(span) = constraint.category
-            {
-                Some(span)
-            } else {
-                None
-            }
-        });
-
-        if let Some(span) = predicate_span {
-            err.span_note(span, "due to current limitations in the borrow checker, this implies a `'static` lifetime");
-        }
-    }
-
-    /// Add a label to region errors and borrow explanations when outlives constraints arise from
-    /// proving a type implements `Sized` or `Copy`.
-    fn add_sized_or_copy_bound_info(
-        &self,
-        err: &mut Diag<'_>,
-        blamed_category: ConstraintCategory<'tcx>,
-        path: &[OutlivesConstraint<'tcx>],
-    ) {
-        for sought_category in [ConstraintCategory::SizedBound, ConstraintCategory::CopyBound] {
-            if sought_category != blamed_category
-                && let Some(sought_constraint) = path.iter().find(|c| c.category == sought_category)
-            {
-                let label = format!(
-                    "requirement occurs due to {}",
-                    sought_category.description().trim_end()
-                );
-                err.span_label(sought_constraint.span, label);
-            }
-        }
-    }
 }
 
 /// The span(s) associated to a use of a place.