Replace unnecessary abort_if_errors.

Replace `abort_if_errors` calls that are certain to abort -- because
we emit an error immediately beforehand -- with `FatalErro.raise()`.

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -3,7 +3,7 @@ use rustc_ast::CRATE_NODE_ID;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::temp_dir::MaybeTempDir;
-use rustc_errors::{DiagCtxt, ErrorGuaranteed};
+use rustc_errors::{DiagCtxt, ErrorGuaranteed, FatalError};
 use rustc_fs_util::{fix_windows_verbatim_for_gcc, try_canonicalize};
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
 use rustc_metadata::find_native_static_library;
@@ -722,10 +722,7 @@ fn link_dwarf_object<'a>(
         Ok(())
     }) {
         Ok(()) => {}
-        Err(e) => {
+        Err(e) => sess.dcx().emit_fatal(errors::ThorinErrorWrapper(e)),
-            sess.dcx().emit_err(errors::ThorinErrorWrapper(e));
-            sess.dcx().abort_if_errors();
-        }
     }
 }
 
@@ -1001,7 +998,7 @@ fn link_natively<'a>(
                 sess.dcx().emit_note(errors::CheckInstalledVisualStudio);
                 sess.dcx().emit_note(errors::InsufficientVSCodeProduct);
             }
-            sess.dcx().abort_if_errors();
+            FatalError.raise();
         }
     }
 

compiler/rustc_codegen_ssa/src/base.rs

@@ -449,10 +449,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         let Some(llfn) = cx.declare_c_main(llfty) else {
             // FIXME: We should be smart and show a better diagnostic here.
             let span = cx.tcx().def_span(rust_main_def_id);
-            let dcx = cx.tcx().dcx();
+            cx.tcx().dcx().emit_fatal(errors::MultipleMainFunctions { span });
-            dcx.emit_err(errors::MultipleMainFunctions { span });
-            dcx.abort_if_errors();
-            bug!();
         };
 
         // `main` should respect same config for frame pointer elimination as rest of code

compiler/rustc_errors/src/lib.rs

@@ -876,6 +876,10 @@ impl DiagCtxt {
         }
     }
 
+    /// This excludes delayed bugs and stashed errors. Used for early aborts
+    /// after errors occurred -- e.g. because continuing in the face of errors is
+    /// likely to lead to bad results, such as spurious/uninteresting
+    /// additional errors -- when returning an error `Result` is difficult.
     pub fn abort_if_errors(&self) {
         if self.has_errors().is_some() {
             FatalError.raise();

compiler/rustc_interface/src/passes.rs

@@ -936,9 +936,7 @@ pub fn start_codegen<'tcx>(
 
     if tcx.sess.opts.output_types.contains_key(&OutputType::Mir) {
         if let Err(error) = rustc_mir_transform::dump_mir::emit_mir(tcx) {
-            let dcx = tcx.dcx();
+            tcx.dcx().emit_fatal(errors::CantEmitMIR { error });
-            dcx.emit_err(errors::CantEmitMIR { error });
-            dcx.abort_if_errors();
         }
     }
 

compiler/rustc_session/src/output.rs

@@ -6,6 +6,7 @@ use crate::errors::{
 };
 use crate::Session;
 use rustc_ast::{self as ast, attr};
+use rustc_errors::FatalError;
 use rustc_span::symbol::sym;
 use rustc_span::{Span, Symbol};
 use std::path::Path;
@@ -115,7 +116,7 @@ pub fn validate_crate_name(sess: &Session, s: Symbol, sp: Option<Span>) {
     }
 
     if err_count > 0 {
-        sess.dcx().abort_if_errors();
+        FatalError.raise();
     }
 }
 

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

@@ -22,7 +22,7 @@ use crate::traits::{
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_errors::{
     codes::*, pluralize, struct_span_code_err, Applicability, DiagnosticBuilder, ErrorGuaranteed,
-    MultiSpan, StashKey, StringPart,
+    FatalError, MultiSpan, StashKey, StringPart,
 };
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Namespace, Res};
@@ -193,14 +193,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         let mut err = self.build_overflow_error(predicate, span, suggest_increasing_limit);
         mutate(&mut err);
         err.emit();
-
+        FatalError.raise();
-        self.dcx().abort_if_errors();
-        // FIXME: this should be something like `build_overflow_error_fatal`, which returns
-        // `DiagnosticBuilder<', !>`. Then we don't even need anything after that `emit()`.
-        unreachable!(
-            "did not expect compilation to continue after `abort_if_errors`, \
-            since an error was definitely emitted!"
-        );
     }
 
     fn build_overflow_error<T>(