Remove DiagnosticBuilder::delay_as_bug_without_consuming.

The existing uses are replaced in one of three ways.
- In a function that also has calls to `emit`, just rearrange the code
  so that exactly one of `delay_as_bug` or `emit` is called on every
  path.
- In a function returning a `DiagnosticBuilder`, use
  `downgrade_to_delayed_bug`. That's good enough because it will get
  emitted later anyway.
- In `unclosed_delim_err`, one set of errors is being replaced with
  another set, so just cancel the original errors.

Author: nnethercote

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -366,13 +366,6 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
         self.emit()
     }
 
-    /// Non-consuming variant of `delay_as_bug`.
-    #[track_caller]
-    pub fn delay_as_bug_without_consuming(&mut self) -> G::EmitResult {
-        self.downgrade_to_delayed_bug();
-        G::emit_producing_guarantee(self)
-    }
-
     forward!((span_label, span_label_mv)(
         span: Span,
         label: impl Into<SubdiagnosticMessage>,

compiler/rustc_hir_typeck/src/intrinsicck.rs

@@ -121,15 +121,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         );
         if from == to {
             err.note(format!("`{from}` does not have a fixed size"));
+            err.emit();
         } else {
             err.note(format!("source type: `{}` ({})", from, skeleton_string(from, sk_from)))
                 .note(format!("target type: `{}` ({})", to, skeleton_string(to, sk_to)));
             if let Err(LayoutError::ReferencesError(_)) = sk_from {
-                err.delay_as_bug_without_consuming();
+                err.delay_as_bug();
             } else if let Err(LayoutError::ReferencesError(_)) = sk_to {
-                err.delay_as_bug_without_consuming();
+                err.delay_as_bug();
+            } else {
+                err.emit();
             }
         }
-        err.emit();
     }
 }

compiler/rustc_hir_typeck/src/op.rs

@@ -385,7 +385,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     && let hir::ExprKind::Assign(..) = expr.kind
                 {
                     // We defer to the later error produced by `check_lhs_assignable`.
-                    err.delay_as_bug_without_consuming();
+                    err.downgrade_to_delayed_bug();
                 }
 
                 let suggest_deref_binop =

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

@@ -361,7 +361,7 @@ pub fn unexpected_hidden_region_diagnostic<'tcx>(
             );
         }
         ty::ReError(_) => {
-            err.delay_as_bug_without_consuming();
+            err.downgrade_to_delayed_bug();
         }
         _ => {
             // Ugh. This is a painful case: the hidden region is not one

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

@@ -281,7 +281,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             }
         };
         if sub.is_error() || sup.is_error() {
-            err.delay_as_bug_without_consuming();
+            err.downgrade_to_delayed_bug();
         }
         err
     }

compiler/rustc_parse/src/lexer/mod.rs

@@ -67,7 +67,7 @@ pub(crate) fn parse_token_trees<'a>(
     let (stream, res, unmatched_delims) =
         tokentrees::TokenTreesReader::parse_all_token_trees(string_reader);
     match res {
-        Ok(_open_spacing) if unmatched_delims.is_empty() => Ok(stream),
+        Ok(()) if unmatched_delims.is_empty() => Ok(stream),
         _ => {
             // Return error if there are unmatched delimiters or unclosed delimiters.
             // We emit delimiter mismatch errors first, then emit the unclosing delimiter mismatch

compiler/rustc_parse/src/lexer/tokentrees.rs

@@ -277,9 +277,9 @@ impl<'a> TokenTreesReader<'a> {
             parser.bump();
         }
         if !diff_errs.is_empty() {
-            errs.iter_mut().for_each(|err| {
-                err.delay_as_bug_without_consuming();
-            });
+            for err in errs {
+                err.cancel();
+            }
             return diff_errs;
         }
         return errs;

compiler/rustc_parse/src/parser/pat.rs

@@ -242,7 +242,7 @@ impl<'a> Parser<'a> {
                 Some(TopLevelOrPatternNotAllowedSugg::WrapInParens { span, pat })
             };
 
-            let mut err = self.dcx().create_err(match syntax_loc {
+            let err = self.dcx().create_err(match syntax_loc {
                 PatternLocation::LetBinding => {
                     TopLevelOrPatternNotAllowed::LetBinding { span, sub }
                 }
@@ -251,9 +251,10 @@ impl<'a> Parser<'a> {
                 }
             });
             if trailing_vert {
-                err.delay_as_bug_without_consuming();
+                err.delay_as_bug();
+            } else {
+                err.emit();
             }
-            err.emit();
         }
 
         Ok((pat, colon))

compiler/rustc_passes/src/errors.rs

@@ -1040,7 +1040,7 @@ impl<'a, G: EmissionGuarantee> IntoDiagnostic<'_, G> for BreakNonLoop<'a> {
                     // This error is redundant, we will have already emitted a
                     // suggestion to use the label when `segment` wasn't found
                     // (hence the `Res::Err` check).
-                    diag.delay_as_bug_without_consuming();
+                    diag.downgrade_to_delayed_bug();
                 }
                 _ => {
                     diag.span_suggestion(

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -2088,7 +2088,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     let ty = self.resolve_vars_if_possible(returned_ty);
                     if ty.references_error() {
                         // don't print out the [type error] here
-                        err.delay_as_bug_without_consuming();
+                        err.downgrade_to_delayed_bug();
                     } else {
                         err.span_label(expr.span, format!("this returned value is of type `{ty}`"));
                     }