Rollup merge of #121085 - davidtwco:always-eager-diagnostics, r=nnethercote

errors: only eagerly translate subdiagnostics

Subdiagnostics don't need to be lazily translated, they can always be eagerly translated. Eager translation is slightly more complex as we need to have a `DiagCtxt` available to perform the translation, which involves slightly more threading of that context.

This slight increase in complexity should enable later simplifications - like passing `DiagCtxt` into `AddToDiagnostic` and moving Fluent messages into the diagnostic structs rather than having them in separate files (working on that was what led to this change).

r? ```@nnethercote```

Author: matthiaskrgr

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -229,7 +229,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 seen_spans.insert(move_span);
             }
 
-            use_spans.var_path_only_subdiag(&mut err, desired_action);
+            use_spans.var_path_only_subdiag(self.dcx(), &mut err, desired_action);
 
             if !is_loop_move {
                 err.span_label(
@@ -291,18 +291,24 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             if needs_note {
                 if let Some(local) = place.as_local() {
                     let span = self.body.local_decls[local].source_info.span;
-                    err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
-                        is_partial_move,
-                        ty,
-                        place: &note_msg,
-                        span,
-                    });
+                    err.subdiagnostic(
+                        self.dcx(),
+                        crate::session_diagnostics::TypeNoCopy::Label {
+                            is_partial_move,
+                            ty,
+                            place: &note_msg,
+                            span,
+                        },
+                    );
                 } else {
-                    err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Note {
-                        is_partial_move,
-                        ty,
-                        place: &note_msg,
-                    });
+                    err.subdiagnostic(
+                        self.dcx(),
+                        crate::session_diagnostics::TypeNoCopy::Note {
+                            is_partial_move,
+                            ty,
+                            place: &note_msg,
+                        },
+                    );
                 };
             }
 
@@ -557,7 +563,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             E0381,
             "{used} binding {desc}{isnt_initialized}"
         );
-        use_spans.var_path_only_subdiag(&mut err, desired_action);
+        use_spans.var_path_only_subdiag(self.dcx(), &mut err, desired_action);
 
         if let InitializationRequiringAction::PartialAssignment
         | InitializationRequiringAction::Assignment = desired_action
@@ -848,9 +854,13 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             &value_msg,
         );
 
-        borrow_spans.var_path_only_subdiag(&mut err, crate::InitializationRequiringAction::Borrow);
+        borrow_spans.var_path_only_subdiag(
+            self.dcx(),
+            &mut err,
+            crate::InitializationRequiringAction::Borrow,
+        );
 
-        move_spans.var_subdiag(None, &mut err, None, |kind, var_span| {
+        move_spans.var_subdiag(self.dcx(), &mut err, None, |kind, var_span| {
             use crate::session_diagnostics::CaptureVarCause::*;
             match kind {
                 hir::ClosureKind::Coroutine(_) => MoveUseInCoroutine { var_span },
@@ -895,7 +905,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             borrow_span,
             &self.describe_any_place(borrow.borrowed_place.as_ref()),
         );
-        borrow_spans.var_subdiag(None, &mut err, Some(borrow.kind), |kind, var_span| {
+        borrow_spans.var_subdiag(self.dcx(), &mut err, Some(borrow.kind), |kind, var_span| {
             use crate::session_diagnostics::CaptureVarCause::*;
             let place = &borrow.borrowed_place;
             let desc_place = self.describe_any_place(place.as_ref());
@@ -1043,7 +1053,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         "mutably borrow",
                     );
                     borrow_spans.var_subdiag(
-                        None,
+                        self.dcx(),
                         &mut err,
                         Some(BorrowKind::Mut { kind: MutBorrowKind::ClosureCapture }),
                         |kind, var_span| {
@@ -1131,22 +1141,31 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         };
 
         if issued_spans == borrow_spans {
-            borrow_spans.var_subdiag(None, &mut err, Some(gen_borrow_kind), |kind, var_span| {
-                use crate::session_diagnostics::CaptureVarCause::*;
-                match kind {
-                    hir::ClosureKind::Coroutine(_) => BorrowUsePlaceCoroutine {
-                        place: desc_place,
-                        var_span,
-                        is_single_var: false,
-                    },
-                    hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
-                        BorrowUsePlaceClosure { place: desc_place, var_span, is_single_var: false }
+            borrow_spans.var_subdiag(
+                self.dcx(),
+                &mut err,
+                Some(gen_borrow_kind),
+                |kind, var_span| {
+                    use crate::session_diagnostics::CaptureVarCause::*;
+                    match kind {
+                        hir::ClosureKind::Coroutine(_) => BorrowUsePlaceCoroutine {
+                            place: desc_place,
+                            var_span,
+                            is_single_var: false,
+                        },
+                        hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
+                            BorrowUsePlaceClosure {
+                                place: desc_place,
+                                var_span,
+                                is_single_var: false,
+                            }
+                        }
                     }
-                }
-            });
+                },
+            );
         } else {
             issued_spans.var_subdiag(
-                Some(self.dcx()),
+                self.dcx(),
                 &mut err,
                 Some(issued_borrow.kind),
                 |kind, var_span| {
@@ -1165,7 +1184,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             );
 
             borrow_spans.var_subdiag(
-                Some(self.dcx()),
+                self.dcx(),
                 &mut err,
                 Some(gen_borrow_kind),
                 |kind, var_span| {
@@ -2217,7 +2236,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             err.span_label(borrow_span, "borrowed value does not live long enough");
             err.span_label(drop_span, format!("`{name}` dropped here while still borrowed"));
 
-            borrow_spans.args_subdiag(&mut err, |args_span| {
+            borrow_spans.args_subdiag(self.dcx(), &mut err, |args_span| {
                 crate::session_diagnostics::CaptureArgLabel::Capture {
                     is_within: borrow_spans.for_coroutine(),
                     args_span,
@@ -2476,7 +2495,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             None,
         );
 
-        borrow_spans.args_subdiag(&mut err, |args_span| {
+        borrow_spans.args_subdiag(self.dcx(), &mut err, |args_span| {
             crate::session_diagnostics::CaptureArgLabel::Capture {
                 is_within: borrow_spans.for_coroutine(),
                 args_span,
@@ -2935,7 +2954,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     "assign",
                 );
 
-                loan_spans.var_subdiag(None, &mut err, Some(loan.kind), |kind, var_span| {
+                loan_spans.var_subdiag(self.dcx(), &mut err, Some(loan.kind), |kind, var_span| {
                     use crate::session_diagnostics::CaptureVarCause::*;
                     match kind {
                         hir::ClosureKind::Coroutine(_) => BorrowUseInCoroutine { var_span },
@@ -2953,7 +2972,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
         let mut err = self.cannot_assign_to_borrowed(span, loan_span, &descr_place);
 
-        loan_spans.var_subdiag(None, &mut err, Some(loan.kind), |kind, var_span| {
+        loan_spans.var_subdiag(self.dcx(), &mut err, Some(loan.kind), |kind, var_span| {
             use crate::session_diagnostics::CaptureVarCause::*;
             match kind {
                 hir::ClosureKind::Coroutine(_) => BorrowUseInCoroutine { var_span },