Auto merge of #120576 - nnethercote:merge-Diagnostic-DiagnosticBuilder, r=<try>

Overhaul `Diagnostic` and `DiagnosticBuilder`

Implements the first part of rust-lang/compiler-team#722, which moves functionality and use away from `Diagnostic`, onto `DiagnosticBuilder`.

Likely follow-ups:
- Move things around, because this PR was written to minimize diff size, so some things end up in sub-optimal places. E.g. `DiagnosticBuilder` has impls in both `diagnostic.rs` and `diagnostic_builder.rs`.
- Rename `Diagnostic` as `DiagInner` and `DiagnosticBuilder` as `Diag`.

r? `@ghost`

Author: bors

Diff for: compiler/rustc_ast_lowering/src/errors.rs

@@ -1,4 +1,7 @@
-use rustc_errors::{codes::*, DiagnosticArgFromDisplay};
+use rustc_errors::{
+    codes::*, AddToDiagnostic, DiagnosticArgFromDisplay, DiagnosticBuilder, EmissionGuarantee,
+    SubdiagnosticMessageOp,
+};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{symbol::Ident, Span, Symbol};
 
@@ -38,14 +41,12 @@ pub struct InvalidAbi {
 
 pub struct InvalidAbiReason(pub &'static str);
 
-impl rustc_errors::AddToDiagnostic for InvalidAbiReason {
-    fn add_to_diagnostic_with<F>(self, diag: &mut rustc_errors::Diagnostic, _: F)
-    where
-        F: Fn(
-            &mut rustc_errors::Diagnostic,
-            rustc_errors::SubdiagnosticMessage,
-        ) -> rustc_errors::SubdiagnosticMessage,
-    {
+impl AddToDiagnostic for InvalidAbiReason {
+    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagnosticMessageOp<G>>(
+        self,
+        diag: &mut DiagnosticBuilder<'_, G>,
+        _: F,
+    ) {
         #[allow(rustc::untranslatable_diagnostic)]
         diag.note(self.0);
     }

Diff for: compiler/rustc_ast_passes/src/errors.rs

@@ -1,7 +1,10 @@
 //! Errors emitted by ast_passes.
 
 use rustc_ast::ParamKindOrd;
-use rustc_errors::{codes::*, AddToDiagnostic, Applicability};
+use rustc_errors::{
+    codes::*, AddToDiagnostic, Applicability, DiagnosticBuilder, EmissionGuarantee,
+    SubdiagnosticMessageOp,
+};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{symbol::Ident, Span, Symbol};
 
@@ -372,13 +375,11 @@ pub struct EmptyLabelManySpans(pub Vec<Span>);
 
 // The derive for `Vec<Span>` does multiple calls to `span_label`, adding commas between each
 impl AddToDiagnostic for EmptyLabelManySpans {
-    fn add_to_diagnostic_with<F>(self, diag: &mut rustc_errors::Diagnostic, _: F)
-    where
-        F: Fn(
-            &mut rustc_errors::Diagnostic,
-            rustc_errors::SubdiagnosticMessage,
-        ) -> rustc_errors::SubdiagnosticMessage,
-    {
+    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagnosticMessageOp<G>>(
+        self,
+        diag: &mut DiagnosticBuilder<'_, G>,
+        _: F,
+    ) {
         diag.span_labels(self.0, "");
     }
 }
@@ -735,13 +736,11 @@ pub struct StableFeature {
 }
 
 impl AddToDiagnostic for StableFeature {
-    fn add_to_diagnostic_with<F>(self, diag: &mut rustc_errors::Diagnostic, _: F)
-    where
-        F: Fn(
-            &mut rustc_errors::Diagnostic,
-            rustc_errors::SubdiagnosticMessage,
-        ) -> rustc_errors::SubdiagnosticMessage,
-    {
+    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagnosticMessageOp<G>>(
+        self,
+        diag: &mut DiagnosticBuilder<'_, G>,
+        _: F,
+    ) {
         diag.arg("name", self.name);
         diag.arg("since", self.since);
         diag.help(fluent::ast_passes_stable_since);

Diff for: compiler/rustc_ast_passes/src/feature_gate.rs

@@ -22,6 +22,9 @@ macro_rules! gate {
     }};
     ($visitor:expr, $feature:ident, $span:expr, $explain:expr, $help:expr) => {{
         if !$visitor.features.$feature && !$span.allows_unstable(sym::$feature) {
+            // FIXME: make this translatable
+            #[allow(rustc::diagnostic_outside_of_impl)]
+            #[allow(rustc::untranslatable_diagnostic)]
             feature_err(&$visitor.sess, sym::$feature, $span, $explain).with_help($help).emit();
         }
     }};

Diff for: compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -3,9 +3,7 @@
 use either::Either;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{
-    codes::*, struct_span_code_err, Applicability, Diagnostic, DiagnosticBuilder, MultiSpan,
-};
+use rustc_errors::{codes::*, struct_span_code_err, Applicability, DiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::{walk_block, walk_expr, Visitor};
@@ -633,7 +631,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     fn suggest_assign_value(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         moved_place: PlaceRef<'tcx>,
         sugg_span: Span,
     ) {
@@ -672,7 +670,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     fn suggest_borrow_fn_like(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         ty: Ty<'tcx>,
         move_sites: &[MoveSite],
         value_name: &str,
@@ -740,7 +738,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     fn suggest_cloning(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         ty: Ty<'tcx>,
         expr: &hir::Expr<'_>,
         span: Span,
@@ -776,7 +774,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         }
     }
 
-    fn suggest_adding_copy_bounds(&self, err: &mut Diagnostic, ty: Ty<'tcx>, span: Span) {
+    fn suggest_adding_copy_bounds(
+        &self,
+        err: &mut DiagnosticBuilder<'_>,
+        ty: Ty<'tcx>,
+        span: Span,
+    ) {
         let tcx = self.infcx.tcx;
         let generics = tcx.generics_of(self.mir_def_id());
 
@@ -1210,7 +1213,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     #[instrument(level = "debug", skip(self, err))]
     fn suggest_using_local_if_applicable(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         location: Location,
         issued_borrow: &BorrowData<'tcx>,
         explanation: BorrowExplanation<'tcx>,
@@ -1306,7 +1309,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     fn suggest_slice_method_if_applicable(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         place: Place<'tcx>,
         borrowed_place: Place<'tcx>,
     ) {
@@ -1415,7 +1418,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     /// ```
     pub(crate) fn explain_iterator_advancement_in_for_loop_if_applicable(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         span: Span,
         issued_spans: &UseSpans<'tcx>,
     ) {
@@ -1602,7 +1605,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     /// ```
     fn suggest_using_closure_argument_instead_of_capture(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         borrowed_place: Place<'tcx>,
         issued_spans: &UseSpans<'tcx>,
     ) {
@@ -1737,7 +1740,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     fn suggest_binding_for_closure_capture_self(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         issued_spans: &UseSpans<'tcx>,
     ) {
         let UseSpans::ClosureUse { capture_kind_span, .. } = issued_spans else { return };
@@ -2984,7 +2987,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         self.buffer_error(err);
     }
 
-    fn explain_deref_coercion(&mut self, loan: &BorrowData<'tcx>, err: &mut Diagnostic) {
+    fn explain_deref_coercion(&mut self, loan: &BorrowData<'tcx>, err: &mut DiagnosticBuilder<'_>) {
         let tcx = self.infcx.tcx;
         if let (
             Some(Terminator {
@@ -3520,7 +3523,11 @@ enum AnnotatedBorrowFnSignature<'tcx> {
 impl<'tcx> AnnotatedBorrowFnSignature<'tcx> {
     /// Annotate the provided diagnostic with information about borrow from the fn signature that
     /// helps explain.
-    pub(crate) fn emit(&self, cx: &mut MirBorrowckCtxt<'_, 'tcx>, diag: &mut Diagnostic) -> String {
+    pub(crate) fn emit(
+        &self,
+        cx: &mut MirBorrowckCtxt<'_, 'tcx>,
+        diag: &mut DiagnosticBuilder<'_>,
+    ) -> String {
         match self {
             &AnnotatedBorrowFnSignature::Closure { argument_ty, argument_span } => {
                 diag.span_label(

Diff for: compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs

@@ -1,6 +1,6 @@
 //! Print diagnostics to explain why values are borrowed.
 
-use rustc_errors::{Applicability, Diagnostic};
+use rustc_errors::{Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
 use rustc_hir::intravisit::Visitor;
 use rustc_index::IndexSlice;
@@ -62,7 +62,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
         tcx: TyCtxt<'tcx>,
         body: &Body<'tcx>,
         local_names: &IndexSlice<Local, Option<Symbol>>,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         borrow_desc: &str,
         borrow_span: Option<Span>,
         multiple_borrow_span: Option<(Span, Span)>,
@@ -303,7 +303,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
     fn add_object_lifetime_default_note(
         &self,
         tcx: TyCtxt<'tcx>,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         unsize_ty: Ty<'tcx>,
     ) {
         if let ty::Adt(def, args) = unsize_ty.kind() {
@@ -356,7 +356,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
 
     fn add_lifetime_bound_suggestion_to_diagnostic(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         category: &ConstraintCategory<'tcx>,
         span: Span,
         region_name: &RegionName,

Diff for: compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -5,7 +5,7 @@ use crate::session_diagnostics::{
     CaptureVarKind, CaptureVarPathUseCause, OnClosureNote,
 };
 use itertools::Itertools;
-use rustc_errors::{Applicability, Diagnostic};
+use rustc_errors::{Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::CoroutineKind;
@@ -80,7 +80,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         &self,
         location: Location,
         place: PlaceRef<'tcx>,
-        diag: &mut Diagnostic,
+        diag: &mut DiagnosticBuilder<'_>,
     ) -> bool {
         debug!("add_moved_or_invoked_closure_note: location={:?} place={:?}", location, place);
         let mut target = place.local_or_deref_local();
@@ -587,7 +587,7 @@ impl UseSpans<'_> {
     /// Add a span label to the arguments of the closure, if it exists.
     pub(super) fn args_subdiag(
         self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         f: impl FnOnce(Span) -> CaptureArgLabel,
     ) {
         if let UseSpans::ClosureUse { args_span, .. } = self {
@@ -599,7 +599,7 @@ impl UseSpans<'_> {
     /// only adds label to the `path_span`
     pub(super) fn var_path_only_subdiag(
         self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         action: crate::InitializationRequiringAction,
     ) {
         use crate::InitializationRequiringAction::*;
@@ -630,7 +630,7 @@ impl UseSpans<'_> {
     pub(super) fn var_subdiag(
         self,
         dcx: Option<&rustc_errors::DiagCtxt>,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         kind: Option<rustc_middle::mir::BorrowKind>,
         f: impl FnOnce(hir::ClosureKind, Span) -> CaptureVarCause,
     ) {
@@ -1002,7 +1002,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     fn explain_captures(
         &mut self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         span: Span,
         move_span: Span,
         move_spans: UseSpans<'tcx>,

Diff for: compiler/rustc_borrowck/src/diagnostics/move_errors.rs

@@ -1,4 +1,4 @@
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder};
+use rustc_errors::{Applicability, DiagnosticBuilder};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty};
 use rustc_mir_dataflow::move_paths::{LookupResult, MovePathIndex};
@@ -434,7 +434,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         err
     }
 
-    fn add_move_hints(&self, error: GroupedMoveError<'tcx>, err: &mut Diagnostic, span: Span) {
+    fn add_move_hints(
+        &self,
+        error: GroupedMoveError<'tcx>,
+        err: &mut DiagnosticBuilder<'_>,
+        span: Span,
+    ) {
         match error {
             GroupedMoveError::MovesFromPlace { mut binds_to, move_from, .. } => {
                 self.add_borrow_suggestions(err, span);
@@ -491,7 +496,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         }
     }
 
-    fn add_borrow_suggestions(&self, err: &mut Diagnostic, span: Span) {
+    fn add_borrow_suggestions(&self, err: &mut DiagnosticBuilder<'_>, span: Span) {
         match self.infcx.tcx.sess.source_map().span_to_snippet(span) {
             Ok(snippet) if snippet.starts_with('*') => {
                 err.span_suggestion_verbose(
@@ -512,7 +517,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         }
     }
 
-    fn add_move_error_suggestions(&self, err: &mut Diagnostic, binds_to: &[Local]) {
+    fn add_move_error_suggestions(&self, err: &mut DiagnosticBuilder<'_>, binds_to: &[Local]) {
         let mut suggestions: Vec<(Span, String, String)> = Vec::new();
         for local in binds_to {
             let bind_to = &self.body.local_decls[*local];
@@ -564,7 +569,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         }
     }
 
-    fn add_move_error_details(&self, err: &mut Diagnostic, binds_to: &[Local]) {
+    fn add_move_error_details(&self, err: &mut DiagnosticBuilder<'_>, binds_to: &[Local]) {
         for (j, local) in binds_to.iter().enumerate() {
             let bind_to = &self.body.local_decls[*local];
             let binding_span = bind_to.source_info.span;
@@ -598,7 +603,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     /// expansion of a packed struct.
     /// Such errors happen because derive macro expansions shy away from taking
     /// references to the struct's fields since doing so would be undefined behaviour
-    fn add_note_for_packed_struct_derive(&self, err: &mut Diagnostic, local: Local) {
+    fn add_note_for_packed_struct_derive(&self, err: &mut DiagnosticBuilder<'_>, local: Local) {
         let local_place: PlaceRef<'tcx> = local.into();
         let local_ty = local_place.ty(self.body.local_decls(), self.infcx.tcx).ty.peel_refs();