Try to explain borrow for tail expr temporary drop order change in 2024

compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs

@@ -5,7 +5,7 @@
 
 use std::assert_matches::assert_matches;
 
-use rustc_errors::{Applicability, Diag};
+use rustc_errors::{Applicability, Diag, EmissionGuarantee};
 use rustc_hir as hir;
 use rustc_hir::intravisit::Visitor;
 use rustc_infer::infer::NllRegionVariableOrigin;
@@ -61,10 +61,10 @@ impl<'tcx> BorrowExplanation<'tcx> {
     pub(crate) fn is_explained(&self) -> bool {
         !matches!(self, BorrowExplanation::Unexplained)
     }
-    pub(crate) fn add_explanation_to_diagnostic(
+    pub(crate) fn add_explanation_to_diagnostic<G: EmissionGuarantee>(
         &self,
         cx: &MirBorrowckCtxt<'_, '_, 'tcx>,
-        err: &mut Diag<'_>,
+        err: &mut Diag<'_, G>,
         borrow_desc: &str,
         borrow_span: Option<Span>,
         multiple_borrow_span: Option<(Span, Span)>,
@@ -346,10 +346,10 @@ impl<'tcx> BorrowExplanation<'tcx> {
         }
     }
 
-    fn add_object_lifetime_default_note(
+    fn add_object_lifetime_default_note<G: EmissionGuarantee>(
         &self,
         tcx: TyCtxt<'tcx>,
-        err: &mut Diag<'_>,
+        err: &mut Diag<'_, G>,
         unsize_ty: Ty<'tcx>,
     ) {
         if let ty::Adt(def, args) = unsize_ty.kind() {
@@ -403,9 +403,9 @@ impl<'tcx> BorrowExplanation<'tcx> {
         }
     }
 
-    fn add_lifetime_bound_suggestion_to_diagnostic(
+    fn add_lifetime_bound_suggestion_to_diagnostic<G: EmissionGuarantee>(
         &self,
-        err: &mut Diag<'_>,
+        err: &mut Diag<'_, G>,
         category: &ConstraintCategory<'tcx>,
         span: Span,
         region_name: &RegionName,
@@ -432,14 +432,14 @@ impl<'tcx> BorrowExplanation<'tcx> {
     }
 }
 
-fn suggest_rewrite_if_let(
+fn suggest_rewrite_if_let<G: EmissionGuarantee>(
     tcx: TyCtxt<'_>,
     expr: &hir::Expr<'_>,
     pat: &str,
     init: &hir::Expr<'_>,
     conseq: &hir::Expr<'_>,
     alt: Option<&hir::Expr<'_>>,
-    err: &mut Diag<'_>,
+    err: &mut Diag<'_, G>,
 ) {
     let source_map = tcx.sess.source_map();
     err.span_note(

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -4,7 +4,7 @@ use std::collections::BTreeMap;
 
 use rustc_abi::{FieldIdx, VariantIdx};
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_errors::{Applicability, Diag, MultiSpan};
+use rustc_errors::{Applicability, Diag, EmissionGuarantee, MultiSpan};
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::{self as hir, CoroutineKind, LangItem};
 use rustc_index::IndexSlice;
@@ -626,9 +626,9 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
 
     /// 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(
+    fn add_placeholder_from_predicate_note<G: EmissionGuarantee>(
         &self,
-        err: &mut Diag<'_>,
+        err: &mut Diag<'_, G>,
         path: &[OutlivesConstraint<'tcx>],
     ) {
         let predicate_span = path.iter().find_map(|constraint| {
@@ -651,9 +651,9 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
 
     /// 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(
+    fn add_sized_or_copy_bound_info<G: EmissionGuarantee>(
         &self,
-        err: &mut Diag<'_>,
+        err: &mut Diag<'_, G>,
         blamed_category: ConstraintCategory<'tcx>,
         path: &[OutlivesConstraint<'tcx>],
     ) {
@@ -1042,6 +1042,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 kind,
             };
         }
+
         normal_ret
     }
 

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -5,7 +5,7 @@ use std::fmt::{self, Display};
 use std::iter;
 
 use rustc_data_structures::fx::IndexEntry;
-use rustc_errors::Diag;
+use rustc_errors::{Diag, EmissionGuarantee};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_middle::ty::print::RegionHighlightMode;
@@ -108,7 +108,7 @@ impl RegionName {
         }
     }
 
-    pub(crate) fn highlight_region_name(&self, diag: &mut Diag<'_>) {
+    pub(crate) fn highlight_region_name<G: EmissionGuarantee>(&self, diag: &mut Diag<'_, G>) {
         match &self.source {
             RegionNameSource::NamedLateParamRegion(span)
             | RegionNameSource::NamedEarlyParamRegion(span) => {

compiler/rustc_borrowck/src/lib.rs

@@ -24,6 +24,7 @@ use std::ops::{ControlFlow, Deref};
 use rustc_abi::FieldIdx;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::graph::dominators::Dominators;
+use rustc_errors::LintDiagnostic;
 use rustc_hir as hir;
 use rustc_hir::CRATE_HIR_ID;
 use rustc_hir::def_id::LocalDefId;
@@ -1192,17 +1193,25 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
             |borrow_index| borrows_in_scope.contains(borrow_index),
             |this, _borrow_index, borrow| {
                 if matches!(borrow.kind, BorrowKind::Fake(_)) {
-                    return Control::Continue;
+                    return ControlFlow::Continue(());
                 }
                 let borrowed = this.retrieve_borrow_spans(borrow).var_or_use_path_span();
-                this.infcx.tcx.emit_node_span_lint(
+                let explain = this.explain_why_borrow_contains_point(
+                    location,
+                    borrow,
+                    Some((WriteKind::StorageDeadOrDrop, place)),
+                );
+                this.infcx.tcx.node_span_lint(
                     TAIL_EXPR_DROP_ORDER,
                     CRATE_HIR_ID,
-                    place_span,
-                    session_diagnostics::TailExprDropOrder { borrowed },
+                    borrowed,
+                    |diag| {
+                        session_diagnostics::TailExprDropOrder { borrowed }.decorate_lint(diag);
+                        explain.add_explanation_to_diagnostic(&this, diag, "", None, None);
+                    },
                 );
                 // We may stop at the first case
-                Control::Break
+                ControlFlow::Break(())
             },
         );
     }