Give `DiagnosticBuilder` a default type.

`IntoDiagnostic` defaults to `ErrorGuaranteed`, because errors are the
most common diagnostic level. It makes sense to do likewise for the
closely-related (and much more widely used) `DiagnosticBuilder` type,
letting us write `DiagnosticBuilder<'a, ErrorGuaranteed>` as just
`DiagnosticBuilder<'a>`. This cuts over 200 lines of code due to many
multi-line things becoming single line things.

5 files changed, 36 insertions, 66 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
index 60dbf7dc055..e6881316a8f 100644
--- a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
@@ -1,7 +1,7 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 
-use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::DiagnosticBuilder;
 use rustc_infer::infer::canonical::Canonical;
 use rustc_infer::infer::error_reporting::nice_region_error::NiceRegionError;
 use rustc_infer::infer::region_constraints::Constraint;
@@ -147,11 +147,7 @@ impl<'tcx> ToUniverseInfo<'tcx> for ! {
 trait TypeOpInfo<'tcx> {
     /// Returns an error to be reported if rerunning the type op fails to
     /// recover the error's cause.
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx>;
 
     fn base_universe(&self) -> ty::UniverseIndex;
 
@@ -161,7 +157,7 @@ trait TypeOpInfo<'tcx> {
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>;
+    ) -> Option<DiagnosticBuilder<'tcx>>;
 
     #[instrument(level = "debug", skip(self, mbcx))]
     fn report_error(
@@ -224,11 +220,7 @@ struct PredicateQuery<'tcx> {
 }
 
 impl<'tcx> TypeOpInfo<'tcx> for PredicateQuery<'tcx> {
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         tcx.sess.create_err(HigherRankedLifetimeError {
             cause: Some(HigherRankedErrorCause::CouldNotProve {
                 predicate: self.canonical_query.value.value.predicate.to_string(),
@@ -247,7 +239,7 @@ impl<'tcx> TypeOpInfo<'tcx> for PredicateQuery<'tcx> {
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         let (infcx, key, _) =
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
         let ocx = ObligationCtxt::new(&infcx);
@@ -265,11 +257,7 @@ impl<'tcx, T> TypeOpInfo<'tcx> for NormalizeQuery<'tcx, T>
 where
     T: Copy + fmt::Display + TypeFoldable<TyCtxt<'tcx>> + 'tcx,
 {
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         tcx.sess.create_err(HigherRankedLifetimeError {
             cause: Some(HigherRankedErrorCause::CouldNotNormalize {
                 value: self.canonical_query.value.value.value.to_string(),
@@ -288,7 +276,7 @@ where
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         let (infcx, key, _) =
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
         let ocx = ObligationCtxt::new(&infcx);
@@ -312,11 +300,7 @@ struct AscribeUserTypeQuery<'tcx> {
 }
 
 impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         // FIXME: This error message isn't great, but it doesn't show up in the existing UI tests,
         // and is only the fallback when the nice error fails. Consider improving this some more.
         tcx.sess.create_err(HigherRankedLifetimeError { cause: None, span })
@@ -332,7 +316,7 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         let (infcx, key, _) =
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
         let ocx = ObligationCtxt::new(&infcx);
@@ -342,11 +326,7 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
 }
 
 impl<'tcx> TypeOpInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
-    fn fallback_error(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        span: Span,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
         // FIXME: This error message isn't great, but it doesn't show up in the existing UI tests,
         // and is only the fallback when the nice error fails. Consider improving this some more.
         tcx.sess.create_err(HigherRankedLifetimeError { cause: None, span })
@@ -362,7 +342,7 @@ impl<'tcx> TypeOpInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
         _cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'tcx>> {
         try_extract_error_from_region_constraints(
             mbcx.infcx,
             placeholder_region,
@@ -383,7 +363,7 @@ fn try_extract_error_from_fulfill_cx<'tcx>(
     ocx: &ObligationCtxt<'_, 'tcx>,
     placeholder_region: ty::Region<'tcx>,
     error_region: Option<ty::Region<'tcx>>,
-) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+) -> Option<DiagnosticBuilder<'tcx>> {
     // We generally shouldn't have errors here because the query was
     // already run, but there's no point using `span_delayed_bug`
     // when we're going to emit an error here anyway.
@@ -407,7 +387,7 @@ fn try_extract_error_from_region_constraints<'tcx>(
     region_constraints: &RegionConstraintData<'tcx>,
     mut region_var_origin: impl FnMut(RegionVid) -> RegionVariableOrigin,
     mut universe_of_region: impl FnMut(RegionVid) -> UniverseIndex,
-) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+) -> Option<DiagnosticBuilder<'tcx>> {
     let placeholder_universe = match placeholder_region.kind() {
         ty::RePlaceholder(p) => p.universe,
         ty::ReVar(vid) => universe_of_region(vid),
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index db0f4559a6b..bd548fd131a 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -2,9 +2,7 @@ use either::Either;
 use hir::PatField;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{
-    struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
-};
+use rustc_errors::{struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::{walk_block, walk_expr, Visitor};
@@ -324,7 +322,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         &mut self,
         mpi: MovePathIndex,
         move_span: Span,
-        err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
+        err: &mut DiagnosticBuilder<'_>,
         in_pattern: &mut bool,
         move_spans: UseSpans<'_>,
     ) {
@@ -483,7 +481,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         desired_action: InitializationRequiringAction,
         span: Span,
         use_spans: UseSpans<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         // We need all statements in the body where the binding was assigned to to later find all
         // the branching code paths where the binding *wasn't* assigned to.
         let inits = &self.move_data.init_path_map[mpi];
@@ -873,7 +871,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         location: Location,
         (place, _span): (Place<'tcx>, Span),
         borrow: &BorrowData<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let borrow_spans = self.retrieve_borrow_spans(borrow);
         let borrow_span = borrow_spans.args_or_use();
 
@@ -921,7 +919,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         (place, span): (Place<'tcx>, Span),
         gen_borrow_kind: BorrowKind,
         issued_borrow: &BorrowData<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let issued_spans = self.retrieve_borrow_spans(issued_borrow);
         let issued_span = issued_spans.args_or_use();
 
@@ -2025,7 +2023,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         drop_span: Span,
         borrow_spans: UseSpans<'tcx>,
         explanation: BorrowExplanation<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         debug!(
             "report_local_value_does_not_live_long_enough(\
              {:?}, {:?}, {:?}, {:?}, {:?}\
@@ -2200,7 +2198,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         &mut self,
         drop_span: Span,
         borrow_span: Span,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         debug!(
             "report_thread_local_value_does_not_live_long_enough(\
              {:?}, {:?}\
@@ -2228,7 +2226,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         borrow_spans: UseSpans<'tcx>,
         proper_span: Span,
         explanation: BorrowExplanation<'tcx>,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         if let BorrowExplanation::MustBeValidFor { category, span, from_closure: false, .. } =
             explanation
         {
@@ -2395,7 +2393,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         return_span: Span,
         category: ConstraintCategory<'tcx>,
         opt_place_desc: Option<&String>,
-    ) -> Option<DiagnosticBuilder<'cx, ErrorGuaranteed>> {
+    ) -> Option<DiagnosticBuilder<'cx>> {
         let return_kind = match category {
             ConstraintCategory::Return(_) => "return",
             ConstraintCategory::Yield => "yield",
@@ -2490,7 +2488,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         constraint_span: Span,
         captured_var: &str,
         scope: &str,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let tcx = self.infcx.tcx;
         let args_span = use_span.args_or_use();
 
@@ -2593,7 +2591,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         upvar_span: Span,
         upvar_name: Symbol,
         escape_span: Span,
-    ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'cx> {
         let tcx = self.infcx.tcx;
 
         let escapes_from = tcx.def_descr(self.mir_def_id().to_def_id());
diff --git a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
index 43487b85a7b..f3b21d22c1a 100644
--- a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
@@ -1,4 +1,4 @@
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty};
 use rustc_mir_dataflow::move_paths::{LookupResult, MovePathIndex};
@@ -288,7 +288,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         &mut self,
         place: Place<'tcx>,
         span: Span,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'a> {
         let description = if place.projection.len() == 1 {
             format!("static item {}", self.describe_any_place(place.as_ref()))
         } else {
@@ -310,7 +310,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         deref_target_place: Place<'tcx>,
         span: Span,
         use_spans: Option<UseSpans<'tcx>>,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'a> {
         // Inspect the type of the content behind the
         // borrow to provide feedback about why this
         // was a move rather than a copy.
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index c3c1f1293d2..506933c470e 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -1,5 +1,5 @@
 use hir::ExprKind;
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder};
 use rustc_hir as hir;
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::Node;
@@ -711,7 +711,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
     fn construct_mut_suggestion_for_local_binding_patterns(
         &self,
-        err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
+        err: &mut DiagnosticBuilder<'_>,
         local: Local,
     ) {
         let local_decl = &self.body.local_decls[local];
@@ -1025,7 +1025,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         }
     }
 
-    fn suggest_using_iter_mut(&self, err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>) {
+    fn suggest_using_iter_mut(&self, err: &mut DiagnosticBuilder<'_>) {
         let source = self.body.source;
         let hir = self.infcx.tcx.hir();
         if let InstanceDef::Item(def_id) = source.instance
@@ -1067,12 +1067,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         }
     }
 
-    fn suggest_make_local_mut(
-        &self,
-        err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
-        local: Local,
-        name: Symbol,
-    ) {
+    fn suggest_make_local_mut(&self, err: &mut DiagnosticBuilder<'_>, local: Local, name: Symbol) {
         let local_decl = &self.body.local_decls[local];
 
         let (pointer_sigil, pointer_desc) =
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 759f5e910f7..e967d9f70ce 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -3,7 +3,7 @@
 //! Error reporting machinery for lifetime errors.
 
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::Res::Def;
 use rustc_hir::def_id::DefId;
@@ -202,7 +202,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     // and the span which bounded to the trait for adding 'static lifetime suggestion
     fn suggest_static_lifetime_for_gat_from_hrtb(
         &self,
-        diag: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
+        diag: &mut DiagnosticBuilder<'_>,
         lower_bound: RegionVid,
     ) {
         let mut suggestions = vec![];
@@ -573,7 +573,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         &self,
         errci: &ErrorConstraintInfo<'tcx>,
         kind: ReturnConstraint,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let ErrorConstraintInfo { outlived_fr, span, .. } = errci;
 
         let mut output_ty = self.regioncx.universal_regions().unnormalized_output_ty;
@@ -645,7 +645,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     fn report_escaping_data_error(
         &self,
         errci: &ErrorConstraintInfo<'tcx>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'tcx> {
         let ErrorConstraintInfo { span, category, .. } = errci;
 
         let fr_name_and_span = self.regioncx.get_var_name_and_span_for_region(
@@ -744,10 +744,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     ///    |     ^^^^^^^^^^^^^^ function was supposed to return data with lifetime `'a` but it
     ///    |                    is returning data with lifetime `'b`
     /// ```
-    fn report_general_error(
-        &self,
-        errci: &ErrorConstraintInfo<'tcx>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    fn report_general_error(&self, errci: &ErrorConstraintInfo<'tcx>) -> DiagnosticBuilder<'tcx> {
         let ErrorConstraintInfo {
             fr,
             fr_is_local,