Auto merge of rust-lang#121285 - nnethercote:delayed_bug-audit, r=lcnr

Delayed bug audit

I went through all the calls to `delayed_bug` and `span_delayed_bug` and found a few places where they could be avoided.

r? `@compiler-errors`

compiler/rustc_ast_lowering/src/delegation.rs

@@ -103,12 +103,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         span: Span,
     ) -> Result<DefId, ErrorGuaranteed> {
         let sig_id = if self.is_in_trait_impl { item_id } else { path_id };
-        let sig_id = self
-            .resolver
-            .get_partial_res(sig_id)
-            .map(|r| r.expect_full_res().opt_def_id())
-            .unwrap_or(None);
-
+        let sig_id =
+            self.resolver.get_partial_res(sig_id).and_then(|r| r.expect_full_res().opt_def_id());
         sig_id.ok_or_else(|| {
             self.tcx
                 .dcx()

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -1,7 +1,7 @@
 //! Error reporting machinery for lifetime errors.
 
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{Applicability, DiagnosticBuilder, MultiSpan};
+use rustc_errors::{Applicability, DiagnosticBuilder, ErrorGuaranteed, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::Res::Def;
 use rustc_hir::def_id::DefId;
@@ -73,7 +73,7 @@ impl<'tcx> ConstraintDescription for ConstraintCategory<'tcx> {
 ///
 /// Usually we expect this to either be empty or contain a small number of items, so we can avoid
 /// allocation most of the time.
-pub(crate) struct RegionErrors<'tcx>(Vec<RegionErrorKind<'tcx>>, TyCtxt<'tcx>);
+pub(crate) struct RegionErrors<'tcx>(Vec<(RegionErrorKind<'tcx>, ErrorGuaranteed)>, TyCtxt<'tcx>);
 
 impl<'tcx> RegionErrors<'tcx> {
     pub fn new(tcx: TyCtxt<'tcx>) -> Self {
@@ -82,15 +82,18 @@ impl<'tcx> RegionErrors<'tcx> {
     #[track_caller]
     pub fn push(&mut self, val: impl Into<RegionErrorKind<'tcx>>) {
         let val = val.into();
-        self.1.sess.dcx().delayed_bug(format!("{val:?}"));
-        self.0.push(val);
+        let guar = self.1.sess.dcx().delayed_bug(format!("{val:?}"));
+        self.0.push((val, guar));
     }
     pub fn is_empty(&self) -> bool {
         self.0.is_empty()
     }
-    pub fn into_iter(self) -> impl Iterator<Item = RegionErrorKind<'tcx>> {
+    pub fn into_iter(self) -> impl Iterator<Item = (RegionErrorKind<'tcx>, ErrorGuaranteed)> {
         self.0.into_iter()
     }
+    pub fn has_errors(&self) -> Option<ErrorGuaranteed> {
+        self.0.get(0).map(|x| x.1)
+    }
 }
 
 impl std::fmt::Debug for RegionErrors<'_> {
@@ -304,10 +307,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         let mut last_unexpected_hidden_region: Option<(Span, Ty<'_>, ty::OpaqueTypeKey<'tcx>)> =
             None;
 
-        for nll_error in nll_errors.into_iter() {
+        for (nll_error, _) in nll_errors.into_iter() {
             match nll_error {
                 RegionErrorKind::TypeTestError { type_test } => {
-                    // Try to convert the lower-bound region into something named we can print for the user.
+                    // Try to convert the lower-bound region into something named we can print for
+                    // the user.
                     let lower_bound_region = self.to_error_region(type_test.lower_bound);
 
                     let type_test_span = type_test.span;

compiler/rustc_borrowck/src/nll.rs

@@ -184,12 +184,9 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
     let (closure_region_requirements, nll_errors) =
         regioncx.solve(infcx, body, polonius_output.clone());
 
-    if !nll_errors.is_empty() {
+    if let Some(guar) = nll_errors.has_errors() {
         // Suppress unhelpful extra errors in `infer_opaque_types`.
-        infcx.set_tainted_by_errors(infcx.dcx().span_delayed_bug(
-            body.span,
-            "`compute_regions` tainted `infcx` with errors but did not emit any errors",
-        ));
+        infcx.set_tainted_by_errors(guar);
     }
 
     let remapped_opaque_tys = regioncx.infer_opaque_types(infcx, opaque_type_values);

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

@@ -311,17 +311,14 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         // Add implied bounds from impl header.
         if matches!(tcx.def_kind(defining_ty_def_id), DefKind::AssocFn | DefKind::AssocConst) {
             for &(ty, _) in tcx.assumed_wf_types(tcx.local_parent(defining_ty_def_id)) {
-                let Ok(TypeOpOutput { output: norm_ty, constraints: c, .. }) = self
+                let result: Result<_, ErrorGuaranteed> = self
                     .param_env
                     .and(type_op::normalize::Normalize::new(ty))
-                    .fully_perform(self.infcx, span)
-                else {
-                    // Note: this path is currently not reached in any test, so
-                    // any example that triggers this would be worth minimizing
-                    // and converting into a test.
-                    tcx.dcx().span_delayed_bug(span, format!("failed to normalize {ty:?}"));
+                    .fully_perform(self.infcx, span);
+                let Ok(TypeOpOutput { output: norm_ty, constraints: c, .. }) = result else {
                     continue;
                 };
+
                 constraints.extend(c);
 
                 // We currently add implied bounds from the normalized ty only.

compiler/rustc_hir_analysis/src/collect.rs

@@ -760,7 +760,7 @@ fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId) {
         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
         prev_discr = Some(
             if let ty::VariantDiscr::Explicit(const_def_id) = variant.discr {
-                def.eval_explicit_discr(tcx, const_def_id)
+                def.eval_explicit_discr(tcx, const_def_id).ok()
             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
                 Some(discr)
             } else {

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -428,6 +428,8 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         generic_param_scope: LocalDefId,
         errors: &[RegionResolutionError<'tcx>],
     ) -> ErrorGuaranteed {
+        assert!(!errors.is_empty());
+
         if let Some(guaranteed) = self.infcx.tainted_by_errors() {
             return guaranteed;
         }
@@ -440,10 +442,13 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
         debug!("report_region_errors: {} errors after preprocessing", errors.len());
 
+        let mut guar = None;
         for error in errors {
             debug!("report_region_errors: error = {:?}", error);
 
-            if !self.try_report_nice_region_error(&error) {
+            guar = Some(if let Some(guar) = self.try_report_nice_region_error(&error) {
+                guar
+            } else {
                 match error.clone() {
                     // These errors could indicate all manner of different
                     // problems with many different solutions. Rather
@@ -454,21 +459,20 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     // general bit of code that displays the error information
                     RegionResolutionError::ConcreteFailure(origin, sub, sup) => {
                         if sub.is_placeholder() || sup.is_placeholder() {
-                            self.report_placeholder_failure(origin, sub, sup).emit();
+                            self.report_placeholder_failure(origin, sub, sup).emit()
                         } else {
-                            self.report_concrete_failure(origin, sub, sup).emit();
+                            self.report_concrete_failure(origin, sub, sup).emit()
                         }
                     }
 
-                    RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => {
-                        self.report_generic_bound_failure(
+                    RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => self
+                        .report_generic_bound_failure(
                             generic_param_scope,
                             origin.span(),
                             Some(origin),
                             param_ty,
                             sub,
-                        );
-                    }
+                        ),
 
                     RegionResolutionError::SubSupConflict(
                         _,
@@ -480,13 +484,13 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         _,
                     ) => {
                         if sub_r.is_placeholder() {
-                            self.report_placeholder_failure(sub_origin, sub_r, sup_r).emit();
+                            self.report_placeholder_failure(sub_origin, sub_r, sup_r).emit()
                         } else if sup_r.is_placeholder() {
-                            self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
+                            self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit()
                         } else {
                             self.report_sub_sup_conflict(
                                 var_origin, sub_origin, sub_r, sup_origin, sup_r,
-                            );
+                            )
                         }
                     }
 
@@ -506,7 +510,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         // value.
                         let sub_r = self.tcx.lifetimes.re_erased;
 
-                        self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
+                        self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit()
                     }
 
                     RegionResolutionError::CannotNormalize(clause, origin) => {
@@ -515,15 +519,13 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         self.tcx
                             .dcx()
                             .struct_span_err(origin.span(), format!("cannot normalize `{clause}`"))
-                            .emit();
+                            .emit()
                     }
                 }
-            }
+            })
         }
 
-        self.tcx
-            .dcx()
-            .span_delayed_bug(self.tcx.def_span(generic_param_scope), "expected region errors")
+        guar.unwrap()
     }
 
     // This method goes through all the errors and try to group certain types
@@ -2314,9 +2316,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         origin: Option<SubregionOrigin<'tcx>>,
         bound_kind: GenericKind<'tcx>,
         sub: Region<'tcx>,
-    ) {
+    ) -> ErrorGuaranteed {
         self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub)
-            .emit();
+            .emit()
     }
 
     pub fn construct_generic_bound_failure(
@@ -2575,7 +2577,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         sub_region: Region<'tcx>,
         sup_origin: SubregionOrigin<'tcx>,
         sup_region: Region<'tcx>,
-    ) {
+    ) -> ErrorGuaranteed {
         let mut err = self.report_inference_failure(var_origin);
 
         note_and_explain_region(
@@ -2614,12 +2616,11 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             );
 
             err.note_expected_found(&"", sup_expected, &"", sup_found);
-            if sub_region.is_error() | sup_region.is_error() {
-                err.delay_as_bug();
+            return if sub_region.is_error() | sup_region.is_error() {
+                err.delay_as_bug()
             } else {
-                err.emit();
-            }
-            return;
+                err.emit()
+            };
         }
 
         self.note_region_origin(&mut err, &sup_origin);
@@ -2634,11 +2635,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         );
 
         self.note_region_origin(&mut err, &sub_origin);
-        if sub_region.is_error() | sup_region.is_error() {
-            err.delay_as_bug();
-        } else {
-            err.emit();
-        }
+        if sub_region.is_error() | sup_region.is_error() { err.delay_as_bug() } else { err.emit() }
     }
 
     /// Determine whether an error associated with the given span and definition

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs

@@ -21,8 +21,11 @@ pub use static_impl_trait::{suggest_new_region_bound, HirTraitObjectVisitor, Tra
 pub use util::find_param_with_region;
 
 impl<'cx, 'tcx> TypeErrCtxt<'cx, 'tcx> {
-    pub fn try_report_nice_region_error(&'cx self, error: &RegionResolutionError<'tcx>) -> bool {
-        NiceRegionError::new(self, error.clone()).try_report().is_some()
+    pub fn try_report_nice_region_error(
+        &'cx self,
+        error: &RegionResolutionError<'tcx>,
+    ) -> Option<ErrorGuaranteed> {
+        NiceRegionError::new(self, error.clone()).try_report()
     }
 }
 

compiler/rustc_middle/src/ty/adt.rs

@@ -7,6 +7,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::HashingControls;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::DefId;
@@ -475,7 +476,11 @@ impl<'tcx> AdtDef<'tcx> {
     }
 
     #[inline]
-    pub fn eval_explicit_discr(self, tcx: TyCtxt<'tcx>, expr_did: DefId) -> Option<Discr<'tcx>> {
+    pub fn eval_explicit_discr(
+        self,
+        tcx: TyCtxt<'tcx>,
+        expr_did: DefId,
+    ) -> Result<Discr<'tcx>, ErrorGuaranteed> {
         assert!(self.is_enum());
         let param_env = tcx.param_env(expr_did);
         let repr_type = self.repr().discr_type();
@@ -484,22 +489,24 @@ impl<'tcx> AdtDef<'tcx> {
                 let ty = repr_type.to_ty(tcx);
                 if let Some(b) = val.try_to_bits_for_ty(tcx, param_env, ty) {
                     trace!("discriminants: {} ({:?})", b, repr_type);
-                    Some(Discr { val: b, ty })
+                    Ok(Discr { val: b, ty })
                 } else {
                     info!("invalid enum discriminant: {:#?}", val);
-                    tcx.dcx().emit_err(crate::error::ConstEvalNonIntError {
+                    let guar = tcx.dcx().emit_err(crate::error::ConstEvalNonIntError {
                         span: tcx.def_span(expr_did),
                     });
-                    None
+                    Err(guar)
                 }
             }
             Err(err) => {
-                let msg = match err {
-                    ErrorHandled::Reported(..) => "enum discriminant evaluation failed",
-                    ErrorHandled::TooGeneric(..) => "enum discriminant depends on generics",
+                let guar = match err {
+                    ErrorHandled::Reported(info, _) => info.into(),
+                    ErrorHandled::TooGeneric(..) => tcx.dcx().span_delayed_bug(
+                        tcx.def_span(expr_did),
+                        "enum discriminant depends on generics",
+                    ),
                 };
-                tcx.dcx().span_delayed_bug(tcx.def_span(expr_did), msg);
-                None
+                Err(guar)
             }
         }
     }
@@ -516,7 +523,7 @@ impl<'tcx> AdtDef<'tcx> {
         self.variants().iter_enumerated().map(move |(i, v)| {
             let mut discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
             if let VariantDiscr::Explicit(expr_did) = v.discr {
-                if let Some(new_discr) = self.eval_explicit_discr(tcx, expr_did) {
+                if let Ok(new_discr) = self.eval_explicit_discr(tcx, expr_did) {
                     discr = new_discr;
                 }
             }
@@ -544,9 +551,13 @@ impl<'tcx> AdtDef<'tcx> {
     ) -> Discr<'tcx> {
         assert!(self.is_enum());
         let (val, offset) = self.discriminant_def_for_variant(variant_index);
-        let explicit_value = val
-            .and_then(|expr_did| self.eval_explicit_discr(tcx, expr_did))
-            .unwrap_or_else(|| self.repr().discr_type().initial_discriminant(tcx));
+        let explicit_value = if let Some(expr_did) = val
+            && let Ok(val) = self.eval_explicit_discr(tcx, expr_did)
+        {
+            val
+        } else {
+            self.repr().discr_type().initial_discriminant(tcx)
+        };
         explicit_value.checked_add(tcx, offset as u128).0
     }
 

compiler/rustc_parse/src/parser/expr.rs

@@ -2688,23 +2688,20 @@ impl<'a> Parser<'a> {
         branch_span: Span,
         attrs: AttrWrapper,
     ) {
-        if attrs.is_empty() {
-            return;
+        if !attrs.is_empty()
+            && let [x0 @ xn] | [x0, .., xn] = &*attrs.take_for_recovery(self.sess)
+        {
+            let attributes = x0.span.to(xn.span);
+            let last = xn.span;
+            let ctx = if is_ctx_else { "else" } else { "if" };
+            self.dcx().emit_err(errors::OuterAttributeNotAllowedOnIfElse {
+                last,
+                branch_span,
+                ctx_span,
+                ctx: ctx.to_string(),
+                attributes,
+            });
         }
-
-        let attrs: &[ast::Attribute] = &attrs.take_for_recovery(self.sess);
-        let (attributes, last) = match attrs {
-            [] => return,
-            [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
-        };
-        let ctx = if is_ctx_else { "else" } else { "if" };
-        self.dcx().emit_err(errors::OuterAttributeNotAllowedOnIfElse {
-            last,
-            branch_span,
-            ctx_span,
-            ctx: ctx.to_string(),
-            attributes,
-        });
     }
 
     fn error_on_extra_if(&mut self, cond: &P<Expr>) -> PResult<'a, ()> {