Avoid a span_delayed_bug in TypeErrCtxt::report_region_errors.

By returning error guarantees from a few functions it relies on.

Author: nnethercote

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()
  }
 }