Auto merge of #121415 - matthiaskrgr:rollup-o9zzet4, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #121206 (Top level error handling)
 - #121261 (coverage: Remove `pending_dups` from the span refiner)
 - #121336 (triagebot: add queue notifications)
 - #121373 (Consistently refer to a test's `revision` instead of `cfg`)
 - #121391 (never patterns: Fix liveness analysis in the presence of never patterns)
 - #121392 (Unify dylib loading between proc macros and codegen backends)
 - #121399 (Solaris linker does not support --strip-debug)
 - #121406 (Add a couple tests)

r? `@ghost`
`@rustbot` modify labels: rollup

31 files changed, 258 insertions, 353 deletions

diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 435b517e602..1ad0dec0640 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/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;
@@ -487,7 +487,9 @@ fn collate_raw_dylibs<'a, 'b>(
             }
         }
     }
-    sess.compile_status()?;
+    if let Some(guar) = sess.dcx().has_errors() {
+        return Err(guar);
+    }
     Ok(dylib_table
         .into_iter()
         .map(|(name, imports)| {
@@ -720,10 +722,7 @@ fn link_dwarf_object<'a>(
         Ok(())
     }) {
         Ok(()) => {}
-        Err(e) => {
-            sess.dcx().emit_err(errors::ThorinErrorWrapper(e));
-            sess.dcx().abort_if_errors();
-        }
+        Err(e) => sess.dcx().emit_fatal(errors::ThorinErrorWrapper(e)),
     }
 }
 
@@ -999,7 +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();
         }
     }
 
diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs
index 9f06f398288..1f3383815e2 100644
--- a/compiler/rustc_codegen_ssa/src/back/linker.rs
+++ b/compiler/rustc_codegen_ssa/src/back/linker.rs
@@ -626,7 +626,7 @@ impl<'a> Linker for GccLinker<'a> {
                 // it does support --strip-all as a compatibility alias for -s.
                 // The --strip-debug case is handled by running an external
                 // `strip` utility as a separate step after linking.
-                if self.sess.target.os != "illumos" {
+                if !self.sess.target.is_like_solaris {
                     self.linker_arg("--strip-debug");
                 }
             }
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 760b3f30ee5..f7afd22a48c 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/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();
-            dcx.emit_err(errors::MultipleMainFunctions { span });
-            dcx.abort_if_errors();
-            bug!();
+            cx.tcx().dcx().emit_fatal(errors::MultipleMainFunctions { span });
         };
 
         // `main` should respect same config for frame pointer elimination as rest of code
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index 60f11b1bdd4..692c059beb0 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -144,16 +144,6 @@ pub const EXIT_FAILURE: i32 = 1;
 pub const DEFAULT_BUG_REPORT_URL: &str = "https://github.com/rust-lang/rust/issues/new\
     ?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md";
 
-pub fn abort_on_err<T>(result: Result<T, ErrorGuaranteed>, sess: &Session) -> T {
-    match result {
-        Err(..) => {
-            sess.dcx().abort_if_errors();
-            panic!("error reported but abort_if_errors didn't abort???");
-        }
-        Ok(x) => x,
-    }
-}
-
 pub trait Callbacks {
     /// Called before creating the compiler instance
     fn config(&mut self, _config: &mut interface::Config) {}
@@ -349,27 +339,33 @@ fn run_compiler(
         },
     };
 
-    callbacks.config(&mut config);
-
-    default_early_dcx.abort_if_errors();
     drop(default_early_dcx);
 
+    callbacks.config(&mut config);
+
     interface::run_compiler(config, |compiler| {
         let sess = &compiler.sess;
         let codegen_backend = &*compiler.codegen_backend;
 
+        // This is used for early exits unrelated to errors. E.g. when just
+        // printing some information without compiling, or exiting immediately
+        // after parsing, etc.
+        let early_exit = || {
+            if let Some(guar) = sess.dcx().has_errors() { Err(guar) } else { Ok(()) }
+        };
+
         // This implements `-Whelp`. It should be handled very early, like
         // `--help`/`-Zhelp`/`-Chelp`. This is the earliest it can run, because
         // it must happen after lints are registered, during session creation.
         if sess.opts.describe_lints {
             describe_lints(sess);
-            return sess.compile_status();
+            return early_exit();
         }
 
         let early_dcx = EarlyDiagCtxt::new(sess.opts.error_format);
 
         if print_crate_info(&early_dcx, codegen_backend, sess, has_input) == Compilation::Stop {
-            return sess.compile_status();
+            return early_exit();
         }
 
         if !has_input {
@@ -378,16 +374,16 @@ fn run_compiler(
 
         if !sess.opts.unstable_opts.ls.is_empty() {
             list_metadata(&early_dcx, sess, &*codegen_backend.metadata_loader());
-            return sess.compile_status();
+            return early_exit();
         }
 
         if sess.opts.unstable_opts.link_only {
             process_rlink(sess, compiler);
-            return sess.compile_status();
+            return early_exit();
         }
 
         let linker = compiler.enter(|queries| {
-            let early_exit = || sess.compile_status().map(|_| None);
+            let early_exit = || early_exit().map(|_| None);
             queries.parse()?;
 
             if let Some(ppm) = &sess.opts.pretty {
@@ -659,10 +655,11 @@ fn process_rlink(sess: &Session, compiler: &interface::Compiler) {
                 };
             }
         };
-        let result = compiler.codegen_backend.link(sess, codegen_results, &outputs);
-        abort_on_err(result, sess);
+        if compiler.codegen_backend.link(sess, codegen_results, &outputs).is_err() {
+            FatalError.raise();
+        }
     } else {
-        dcx.emit_fatal(RlinkNotAFile {})
+        dcx.emit_fatal(RlinkNotAFile {});
     }
 }
 
diff --git a/compiler/rustc_driver_impl/src/pretty.rs b/compiler/rustc_driver_impl/src/pretty.rs
index e5a7d550115..ff5ffd2454a 100644
--- a/compiler/rustc_driver_impl/src/pretty.rs
+++ b/compiler/rustc_driver_impl/src/pretty.rs
@@ -2,6 +2,7 @@
 
 use rustc_ast as ast;
 use rustc_ast_pretty::pprust as pprust_ast;
+use rustc_errors::FatalError;
 use rustc_hir as hir;
 use rustc_hir_pretty as pprust_hir;
 use rustc_middle::bug;
@@ -18,7 +19,6 @@ use std::fmt::Write;
 
 pub use self::PpMode::*;
 pub use self::PpSourceMode::*;
-use crate::abort_on_err;
 
 struct AstNoAnn;
 
@@ -243,7 +243,9 @@ impl<'tcx> PrintExtra<'tcx> {
 
 pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
     if ppm.needs_analysis() {
-        abort_on_err(ex.tcx().analysis(()), sess);
+        if ex.tcx().analysis(()).is_err() {
+            FatalError.raise();
+        }
     }
 
     let (src, src_name) = get_source(sess);
@@ -334,7 +336,9 @@ pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
         ThirTree => {
             let tcx = ex.tcx();
             let mut out = String::new();
-            abort_on_err(rustc_hir_analysis::check_crate(tcx), tcx.sess);
+            if rustc_hir_analysis::check_crate(tcx).is_err() {
+                FatalError.raise();
+            }
             debug!("pretty printing THIR tree");
             for did in tcx.hir().body_owners() {
                 let _ = writeln!(out, "{:?}:\n{}\n", did, tcx.thir_tree(did));
@@ -344,7 +348,9 @@ pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
         ThirFlat => {
             let tcx = ex.tcx();
             let mut out = String::new();
-            abort_on_err(rustc_hir_analysis::check_crate(tcx), tcx.sess);
+            if rustc_hir_analysis::check_crate(tcx).is_err() {
+                FatalError.raise();
+            }
             debug!("pretty printing THIR flat");
             for did in tcx.hir().body_owners() {
                 let _ = writeln!(out, "{:?}:\n{}\n", did, tcx.thir_flat(did));
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 052d9b3a783..7e3d15ffc92 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -471,9 +471,10 @@ struct DiagCtxtInner {
     emitted_diagnostics: FxHashSet<Hash128>,
 
     /// Stashed diagnostics emitted in one stage of the compiler that may be
-    /// stolen by other stages (e.g. to improve them and add more information).
-    /// The stashed diagnostics count towards the total error count.
-    /// When `.abort_if_errors()` is called, these are also emitted.
+    /// stolen and emitted/cancelled by other stages (e.g. to improve them and
+    /// add more information). All stashed diagnostics must be emitted with
+    /// `emit_stashed_diagnostics` by the time the `DiagCtxtInner` is dropped,
+    /// otherwise an assertion failure will occur.
     stashed_diagnostics: FxIndexMap<(Span, StashKey), Diagnostic>,
 
     future_breakage_diagnostics: Vec<Diagnostic>,
@@ -558,7 +559,9 @@ pub struct DiagCtxtFlags {
 
 impl Drop for DiagCtxtInner {
     fn drop(&mut self) {
-        self.emit_stashed_diagnostics();
+        // Any stashed diagnostics should have been handled by
+        // `emit_stashed_diagnostics` by now.
+        assert!(self.stashed_diagnostics.is_empty());
 
         if self.err_guars.is_empty() {
             self.flush_delayed()
@@ -750,17 +753,24 @@ impl DiagCtxt {
     }
 
     /// Emit all stashed diagnostics.
-    pub fn emit_stashed_diagnostics(&self) {
+    pub fn emit_stashed_diagnostics(&self) -> Option<ErrorGuaranteed> {
         self.inner.borrow_mut().emit_stashed_diagnostics()
     }
 
-    /// This excludes lint errors, delayed bugs, and stashed errors.
+    /// This excludes lint errors, delayed bugs and stashed errors.
     #[inline]
-    pub fn err_count(&self) -> usize {
+    pub fn err_count_excluding_lint_errs(&self) -> usize {
         self.inner.borrow().err_guars.len()
     }
 
-    /// This excludes normal errors, lint errors and delayed bugs. Unless
+    /// This excludes delayed bugs and stashed errors.
+    #[inline]
+    pub fn err_count(&self) -> usize {
+        let inner = self.inner.borrow();
+        inner.err_guars.len() + inner.lint_err_guars.len()
+    }
+
+    /// This excludes normal errors, lint errors, and delayed bugs. Unless
     /// absolutely necessary, avoid using this. It's dubious because stashed
     /// errors can later be cancelled, so the presence of a stashed error at
     /// some point of time doesn't guarantee anything -- there are no
@@ -769,27 +779,29 @@ impl DiagCtxt {
         self.inner.borrow().stashed_err_count
     }
 
-    /// This excludes lint errors, delayed bugs, and stashed errors.
-    pub fn has_errors(&self) -> Option<ErrorGuaranteed> {
-        self.inner.borrow().has_errors()
+    /// This excludes lint errors, delayed bugs, and stashed errors. Unless
+    /// absolutely necessary, prefer `has_errors` to this method.
+    pub fn has_errors_excluding_lint_errors(&self) -> Option<ErrorGuaranteed> {
+        self.inner.borrow().has_errors_excluding_lint_errors()
     }
 
-    /// This excludes delayed bugs and stashed errors. Unless absolutely
-    /// necessary, prefer `has_errors` to this method.
-    pub fn has_errors_or_lint_errors(&self) -> Option<ErrorGuaranteed> {
-        self.inner.borrow().has_errors_or_lint_errors()
+    /// This excludes delayed bugs and stashed errors.
+    pub fn has_errors(&self) -> Option<ErrorGuaranteed> {
+        self.inner.borrow().has_errors()
     }
 
     /// This excludes stashed errors. Unless absolutely necessary, prefer
-    /// `has_errors` or `has_errors_or_lint_errors` to this method.
-    pub fn has_errors_or_lint_errors_or_delayed_bugs(&self) -> Option<ErrorGuaranteed> {
-        self.inner.borrow().has_errors_or_lint_errors_or_delayed_bugs()
+    /// `has_errors` to this method.
+    pub fn has_errors_or_delayed_bugs(&self) -> Option<ErrorGuaranteed> {
+        self.inner.borrow().has_errors_or_delayed_bugs()
     }
 
     pub fn print_error_count(&self, registry: &Registry) {
         let mut inner = self.inner.borrow_mut();
 
-        inner.emit_stashed_diagnostics();
+        // Any stashed diagnostics should have been handled by
+        // `emit_stashed_diagnostics` by now.
+        assert!(inner.stashed_diagnostics.is_empty());
 
         if inner.treat_err_as_bug() {
             return;
@@ -864,10 +876,12 @@ 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) {
-        let mut inner = self.inner.borrow_mut();
-        inner.emit_stashed_diagnostics();
-        if !inner.err_guars.is_empty() {
+        if self.has_errors().is_some() {
             FatalError.raise();
         }
     }
@@ -1268,10 +1282,10 @@ impl DiagCtxt {
 // `DiagCtxtInner::foo`.
 impl DiagCtxtInner {
     /// Emit all stashed diagnostics.
-    fn emit_stashed_diagnostics(&mut self) {
+    fn emit_stashed_diagnostics(&mut self) -> Option<ErrorGuaranteed> {
+        let mut guar = None;
         let has_errors = !self.err_guars.is_empty();
         for (_, diag) in std::mem::take(&mut self.stashed_diagnostics).into_iter() {
-            // Decrement the count tracking the stash; emitting will increment it.
             if diag.is_error() {
                 if diag.is_lint.is_none() {
                     self.stashed_err_count -= 1;
@@ -1284,8 +1298,9 @@ impl DiagCtxtInner {
                     continue;
                 }
             }
-            self.emit_diagnostic(diag);
+            guar = guar.or(self.emit_diagnostic(diag));
         }
+        guar
     }
 
     // Return value is only `Some` if the level is `Error` or `DelayedBug`.
@@ -1329,7 +1344,7 @@ impl DiagCtxtInner {
             DelayedBug => {
                 // If we have already emitted at least one error, we don't need
                 // to record the delayed bug, because it'll never be used.
-                return if let Some(guar) = self.has_errors_or_lint_errors() {
+                return if let Some(guar) = self.has_errors() {
                     Some(guar)
                 } else {
                     let backtrace = std::backtrace::Backtrace::capture();
@@ -1445,17 +1460,16 @@ impl DiagCtxtInner {
             .is_some_and(|c| self.err_guars.len() + self.lint_err_guars.len() + 1 >= c.get())
     }
 
-    fn has_errors(&self) -> Option<ErrorGuaranteed> {
+    fn has_errors_excluding_lint_errors(&self) -> Option<ErrorGuaranteed> {
         self.err_guars.get(0).copied()
     }
 
-    fn has_errors_or_lint_errors(&self) -> Option<ErrorGuaranteed> {
-        self.has_errors().or_else(|| self.lint_err_guars.get(0).copied())
+    fn has_errors(&self) -> Option<ErrorGuaranteed> {
+        self.has_errors_excluding_lint_errors().or_else(|| self.lint_err_guars.get(0).copied())
     }
 
-    fn has_errors_or_lint_errors_or_delayed_bugs(&self) -> Option<ErrorGuaranteed> {
-        self.has_errors_or_lint_errors()
-            .or_else(|| self.delayed_bugs.get(0).map(|(_, guar)| guar).copied())
+    fn has_errors_or_delayed_bugs(&self) -> Option<ErrorGuaranteed> {
+        self.has_errors().or_else(|| self.delayed_bugs.get(0).map(|(_, guar)| guar).copied())
     }
 
     /// Translate `message` eagerly with `args` to `SubdiagnosticMessage::Eager`.
@@ -1488,6 +1502,11 @@ impl DiagCtxtInner {
     }
 
     fn flush_delayed(&mut self) {
+        // Stashed diagnostics must be emitted before delayed bugs are flushed.
+        // Otherwise, we might ICE prematurely when errors would have
+        // eventually happened.
+        assert!(self.stashed_diagnostics.is_empty());
+
         if self.delayed_bugs.is_empty() {
             return;
         }
diff --git a/compiler/rustc_hir/src/pat_util.rs b/compiler/rustc_hir/src/pat_util.rs
index e6050327186..1eaab3d2aca 100644
--- a/compiler/rustc_hir/src/pat_util.rs
+++ b/compiler/rustc_hir/src/pat_util.rs
@@ -71,14 +71,21 @@ impl hir::Pat<'_> {
     /// Call `f` on every "binding" in a pattern, e.g., on `a` in
     /// `match foo() { Some(a) => (), None => () }`.
     ///
-    /// When encountering an or-pattern `p_0 | ... | p_n` only `p_0` will be visited.
+    /// When encountering an or-pattern `p_0 | ... | p_n` only the first non-never pattern will be
+    /// visited. If they're all never patterns we visit nothing, which is ok since a never pattern
+    /// cannot have bindings.
     pub fn each_binding_or_first(
         &self,
         f: &mut impl FnMut(hir::BindingAnnotation, HirId, Span, Ident),
     ) {
         self.walk(|p| match &p.kind {
             PatKind::Or(ps) => {
-                ps[0].each_binding_or_first(f);
+                for p in *ps {
+                    if !p.is_never_pattern() {
+                        p.each_binding_or_first(f);
+                        break;
+                    }
+                }
                 false
             }
             PatKind::Binding(bm, _, ident, _) => {
diff --git a/compiler/rustc_incremental/src/persist/fs.rs b/compiler/rustc_incremental/src/persist/fs.rs
index 23d29916922..dd9c16d006a 100644
--- a/compiler/rustc_incremental/src/persist/fs.rs
+++ b/compiler/rustc_incremental/src/persist/fs.rs
@@ -312,7 +312,7 @@ pub fn finalize_session_directory(sess: &Session, svh: Option<Svh>) {
 
     let incr_comp_session_dir: PathBuf = sess.incr_comp_session_dir().clone();
 
-    if sess.dcx().has_errors_or_lint_errors_or_delayed_bugs().is_some() {
+    if sess.dcx().has_errors_or_delayed_bugs().is_some() {
         // If there have been any errors during compilation, we don't want to
         // publish this session directory. Rather, we'll just delete it.
 
diff --git a/compiler/rustc_incremental/src/persist/save.rs b/compiler/rustc_incremental/src/persist/save.rs
index ff0c58d09de..32759f5284a 100644
--- a/compiler/rustc_incremental/src/persist/save.rs
+++ b/compiler/rustc_incremental/src/persist/save.rs
@@ -32,7 +32,7 @@ pub fn save_dep_graph(tcx: TyCtxt<'_>) {
             return;
         }
         // This is going to be deleted in finalize_session_directory, so let's not create it.
-        if sess.dcx().has_errors_or_lint_errors_or_delayed_bugs().is_some() {
+        if sess.dcx().has_errors_or_delayed_bugs().is_some() {
             return;
         }
 
@@ -87,7 +87,7 @@ pub fn save_work_product_index(
         return;
     }
     // This is going to be deleted in finalize_session_directory, so let's not create it
-    if sess.dcx().has_errors_or_lint_errors().is_some() {
+    if sess.dcx().has_errors().is_some() {
         return;
     }
 
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index 60711ffeb2c..8fc71671b27 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -712,7 +712,7 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
             reported_trait_errors: Default::default(),
             reported_signature_mismatch: Default::default(),
             tainted_by_errors: Cell::new(None),
-            err_count_on_creation: tcx.dcx().err_count(),
+            err_count_on_creation: tcx.dcx().err_count_excluding_lint_errs(),
             stashed_err_count_on_creation: tcx.dcx().stashed_err_count(),
             universe: Cell::new(ty::UniverseIndex::ROOT),
             intercrate,
@@ -1267,8 +1267,11 @@ impl<'tcx> InferCtxt<'tcx> {
     pub fn tainted_by_errors(&self) -> Option<ErrorGuaranteed> {
         if let Some(guar) = self.tainted_by_errors.get() {
             Some(guar)
-        } else if self.dcx().err_count() > self.err_count_on_creation {
-            // Errors reported since this infcx was made.
+        } else if self.dcx().err_count_excluding_lint_errs() > self.err_count_on_creation {
+            // Errors reported since this infcx was made. Lint errors are
+            // excluded to avoid some being swallowed in the presence of
+            // non-lint errors. (It's arguable whether or not this exclusion is
+            // important.)
             let guar = self.dcx().has_errors().unwrap();
             self.set_tainted_by_errors(guar);
             Some(guar)
diff --git a/compiler/rustc_interface/Cargo.toml b/compiler/rustc_interface/Cargo.toml
index a238eacda44..0e90836145e 100644
--- a/compiler/rustc_interface/Cargo.toml
+++ b/compiler/rustc_interface/Cargo.toml
@@ -5,7 +5,6 @@ edition = "2021"
 
 [dependencies]
 # tidy-alphabetical-start
-libloading = "0.8.0"
 rustc-rayon = { version = "0.5.0", optional = true }
 rustc-rayon-core = { version = "0.5.0", optional = true }
 rustc_ast = { path = "../rustc_ast" }
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 8a4705e0056..cd7957c3bce 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -423,18 +423,43 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                 Compiler { sess, codegen_backend, override_queries: config.override_queries };
 
             rustc_span::set_source_map(compiler.sess.parse_sess.clone_source_map(), move || {
-                let r = {
-                    let _sess_abort_error = defer(|| {
-                        compiler.sess.finish_diagnostics(&config.registry);
+                // There are two paths out of `f`.
+                // - Normal exit.
+                // - Panic, e.g. triggered by `abort_if_errors`.
+                //
+                // We must run `finish_diagnostics` in both cases.
+                let res = {
+                    // If `f` panics, `finish_diagnostics` will run during
+                    // unwinding because of the `defer`.
+                    let mut guar = None;
+                    let sess_abort_guard = defer(|| {
+                        guar = compiler.sess.finish_diagnostics(&config.registry);
                     });
 
-                    f(&compiler)
+                    let res = f(&compiler);
+
+                    // If `f` doesn't panic, `finish_diagnostics` will run
+                    // normally when `sess_abort_guard` is dropped.
+                    drop(sess_abort_guard);
+
+                    // If `finish_diagnostics` emits errors (e.g. stashed
+                    // errors) we can't return an error directly, because the
+                    // return type of this function is `R`, not `Result<R, E>`.
+                    // But we need to communicate the errors' existence to the
+                    // caller, otherwise the caller might mistakenly think that
+                    // no errors occurred and return a zero exit code. So we
+                    // abort (panic) instead, similar to if `f` had panicked.
+                    if guar.is_some() {
+                        compiler.sess.dcx().abort_if_errors();
+                    }
+
+                    res
                 };
 
                 let prof = compiler.sess.prof.clone();
-
                 prof.generic_activity("drop_compiler").run(move || drop(compiler));
-                r
+
+                res
             })
         },
     )
diff --git a/compiler/rustc_interface/src/lib.rs b/compiler/rustc_interface/src/lib.rs
index 24c2e290534..d0ce23dacb5 100644
--- a/compiler/rustc_interface/src/lib.rs
+++ b/compiler/rustc_interface/src/lib.rs
@@ -1,5 +1,4 @@
 #![feature(decl_macro)]
-#![feature(error_iter)]
 #![feature(generic_nonzero)]
 #![feature(lazy_cell)]
 #![feature(let_chains)]
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 60d13f02ad7..66140168759 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -772,12 +772,11 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
     // lot of annoying errors in the ui tests (basically,
     // lint warnings and so on -- kindck used to do this abort, but
     // kindck is gone now). -nmatsakis
-    if let Some(reported) = sess.dcx().has_errors() {
-        return Err(reported);
-    } else if sess.dcx().stashed_err_count() > 0 {
-        // Without this case we sometimes get delayed bug ICEs and I don't
-        // understand why. -nnethercote
-        return Err(sess.dcx().delayed_bug("some stashed error is waiting for use"));
+    //
+    // But we exclude lint errors from this, because lint errors are typically
+    // less serious and we're more likely to want to continue (#87337).
+    if let Some(guar) = sess.dcx().has_errors_excluding_lint_errors() {
+        return Err(guar);
     }
 
     sess.time("misc_checking_3", || {
@@ -937,9 +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();
-            dcx.emit_err(errors::CantEmitMIR { error });
-            dcx.abort_if_errors();
+            tcx.dcx().emit_fatal(errors::CantEmitMIR { error });
         }
     }
 
diff --git a/compiler/rustc_interface/src/queries.rs b/compiler/rustc_interface/src/queries.rs
index 211bcb9da94..86858bfe41d 100644
--- a/compiler/rustc_interface/src/queries.rs
+++ b/compiler/rustc_interface/src/queries.rs
@@ -222,12 +222,12 @@ impl<'tcx> Queries<'tcx> {
 
     pub fn codegen_and_build_linker(&'tcx self) -> Result<Linker> {
         self.global_ctxt()?.enter(|tcx| {
-            // Don't do code generation if there were any errors
-            self.compiler.sess.compile_status()?;
-
-            // If we have any delayed bugs, for example because we created TyKind::Error earlier,
-            // it's likely that codegen will only cause more ICEs, obscuring the original problem
-            self.compiler.sess.dcx().flush_delayed();
+            // Don't do code generation if there were any errors. Likewise if
+            // there were any delayed bugs, because codegen will likely cause
+            // more ICEs, obscuring the original problem.
+            if let Some(guar) = self.compiler.sess.dcx().has_errors_or_delayed_bugs() {
+                return Err(guar);
+            }
 
             // Hook for UI tests.
             Self::check_for_rustc_errors_attr(tcx);
@@ -261,7 +261,9 @@ impl Linker {
         let (codegen_results, work_products) =
             codegen_backend.join_codegen(self.ongoing_codegen, sess, &self.output_filenames);
 
-        sess.compile_status()?;
+        if let Some(guar) = sess.dcx().has_errors() {
+            return Err(guar);
+        }
 
         sess.time("serialize_work_products", || {
             rustc_incremental::save_work_product_index(sess, &self.dep_graph, work_products)
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 087c43075f1..823614e1f06 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -1,10 +1,10 @@
 use crate::errors;
 use info;
-use libloading::Library;
 use rustc_ast as ast;
 use rustc_codegen_ssa::traits::CodegenBackend;
 #[cfg(parallel_compiler)]
 use rustc_data_structures::sync;
+use rustc_metadata::{load_symbol_from_dylib, DylibError};
 use rustc_parse::validate_attr;
 use rustc_session as session;
 use rustc_session::config::{self, Cfg, CrateType, OutFileName, OutputFilenames, OutputTypes};
@@ -17,7 +17,6 @@ use rustc_span::symbol::{sym, Symbol};
 use session::EarlyDiagCtxt;
 use std::env;
 use std::env::consts::{DLL_PREFIX, DLL_SUFFIX};
-use std::mem;
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::OnceLock;
@@ -162,29 +161,19 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce() -> R + Send, R: Send>(
 }
 
 fn load_backend_from_dylib(early_dcx: &EarlyDiagCtxt, path: &Path) -> MakeBackendFn {
-    fn format_err(e: &(dyn std::error::Error + 'static)) -> String {
-        e.sources().map(|e| format!(": {e}")).collect()
-    }
-    let lib = unsafe { Library::new(path) }.unwrap_or_else(|err| {
-        let err = format!("couldn't load codegen backend {path:?}{}", format_err(&err));
-        early_dcx.early_fatal(err);
-    });
-
-    let backend_sym = unsafe { lib.get::<MakeBackendFn>(b"__rustc_codegen_backend") }
-        .unwrap_or_else(|e| {
+    match unsafe { load_symbol_from_dylib::<MakeBackendFn>(path, "__rustc_codegen_backend") } {
+        Ok(backend_sym) => backend_sym,
+        Err(DylibError::DlOpen(path, err)) => {
+            let err = format!("couldn't load codegen backend {path}{err}");
+            early_dcx.early_fatal(err);
+        }
+        Err(DylibError::DlSym(_path, err)) => {
             let e = format!(
-                "`__rustc_codegen_backend` symbol lookup in the codegen backend failed{}",
-                format_err(&e)
+                "`__rustc_codegen_backend` symbol lookup in the codegen backend failed{err}",
             );
             early_dcx.early_fatal(e);
-        });
-
-    // Intentionally leak the dynamic library. We can't ever unload it
-    // since the library can make things that will live arbitrarily long.
-    let backend_sym = unsafe { backend_sym.into_raw() };
-    mem::forget(lib);
-
-    *backend_sym
+        }
+    }
 }
 
 /// Get the codegen backend based on the name and specified sysroot.
diff --git a/compiler/rustc_metadata/messages.ftl b/compiler/rustc_metadata/messages.ftl
index 8da6f0007f0..a1c6fba4d43 100644
--- a/compiler/rustc_metadata/messages.ftl
+++ b/compiler/rustc_metadata/messages.ftl
@@ -45,7 +45,7 @@ metadata_crate_not_panic_runtime =
     the crate `{$crate_name}` is not a panic runtime
 
 metadata_dl_error =
-    {$err}
+    {$path}{$err}
 
 metadata_empty_link_name =
     link name must not be empty
diff --git a/compiler/rustc_metadata/src/creader.rs b/compiler/rustc_metadata/src/creader.rs
index f6d3dba2470..f65fe1a29c7 100644
--- a/compiler/rustc_metadata/src/creader.rs
+++ b/compiler/rustc_metadata/src/creader.rs
@@ -692,20 +692,8 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
         path: &Path,
         stable_crate_id: StableCrateId,
     ) -> Result<&'static [ProcMacro], CrateError> {
-        // Make sure the path contains a / or the linker will search for it.
-        let path = try_canonicalize(path).unwrap();
-        let lib = load_dylib(&path, 5).map_err(|err| CrateError::DlOpen(err))?;
-
         let sym_name = self.sess.generate_proc_macro_decls_symbol(stable_crate_id);
-        let sym = unsafe { lib.get::<*const &[ProcMacro]>(sym_name.as_bytes()) }
-            .map_err(|err| CrateError::DlSym(err.to_string()))?;
-
-        // Intentionally leak the dynamic library. We can't ever unload it
-        // since the library can make things that will live arbitrarily long.
-        let sym = unsafe { sym.into_raw() };
-        std::mem::forget(lib);
-
-        Ok(unsafe { **sym })
+        Ok(unsafe { *load_symbol_from_dylib::<*const &[ProcMacro]>(path, &sym_name)? })
     }
 
     fn inject_panic_runtime(&mut self, krate: &ast::Crate) {
@@ -926,7 +914,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
         what: &str,
         needs_dep: &dyn Fn(&CrateMetadata) -> bool,
     ) {
-        // don't perform this validation if the session has errors, as one of
+        // Don't perform this validation if the session has errors, as one of
         // those errors may indicate a circular dependency which could cause
         // this to stack overflow.
         if self.dcx().has_errors().is_some() {
@@ -1116,6 +1104,10 @@ fn alloc_error_handler_spans(krate: &ast::Crate) -> Vec<Span> {
     f.spans
 }
 
+fn format_dlopen_err(e: &(dyn std::error::Error + 'static)) -> String {
+    e.sources().map(|e| format!(": {e}")).collect()
+}
+
 // On Windows the compiler would sometimes intermittently fail to open the
 // proc-macro DLL with `Error::LoadLibraryExW`. It is suspected that something in the
 // system still holds a lock on the file, so we retry a few times before calling it
@@ -1154,9 +1146,43 @@ fn load_dylib(path: &Path, max_attempts: usize) -> Result<libloading::Library, S
 
     let last_error = last_error.unwrap();
     let message = if let Some(src) = last_error.source() {
-        format!("{last_error} ({src}) (retried {max_attempts} times)")
+        format!("{} ({src}) (retried {max_attempts} times)", format_dlopen_err(&last_error))
     } else {
-        format!("{last_error} (retried {max_attempts} times)")
+        format!("{} (retried {max_attempts} times)", format_dlopen_err(&last_error))
     };
     Err(message)
 }
+
+pub enum DylibError {
+    DlOpen(String, String),
+    DlSym(String, String),
+}
+
+impl From<DylibError> for CrateError {
+    fn from(err: DylibError) -> CrateError {
+        match err {
+            DylibError::DlOpen(path, err) => CrateError::DlOpen(path, err),
+            DylibError::DlSym(path, err) => CrateError::DlSym(path, err),
+        }
+    }
+}
+
+pub unsafe fn load_symbol_from_dylib<T: Copy>(
+    path: &Path,
+    sym_name: &str,
+) -> Result<T, DylibError> {
+    // Make sure the path contains a / or the linker will search for it.
+    let path = try_canonicalize(path).unwrap();
+    let lib =
+        load_dylib(&path, 5).map_err(|err| DylibError::DlOpen(path.display().to_string(), err))?;
+
+    let sym = unsafe { lib.get::<T>(sym_name.as_bytes()) }
+        .map_err(|err| DylibError::DlSym(path.display().to_string(), format_dlopen_err(&err)))?;
+
+    // Intentionally leak the dynamic library. We can't ever unload it
+    // since the library can make things that will live arbitrarily long.
+    let sym = unsafe { sym.into_raw() };
+    std::mem::forget(lib);
+
+    Ok(*sym)
+}
diff --git a/compiler/rustc_metadata/src/errors.rs b/compiler/rustc_metadata/src/errors.rs
index 7e0a4fb72d4..9a05d9ac0de 100644
--- a/compiler/rustc_metadata/src/errors.rs
+++ b/compiler/rustc_metadata/src/errors.rs
@@ -535,6 +535,7 @@ pub struct StableCrateIdCollision {
 pub struct DlError {
     #[primary_span]
     pub span: Span,
+    pub path: String,
     pub err: String,
 }
 
diff --git a/compiler/rustc_metadata/src/lib.rs b/compiler/rustc_metadata/src/lib.rs
index 70ad8598957..f133a2f5f73 100644
--- a/compiler/rustc_metadata/src/lib.rs
+++ b/compiler/rustc_metadata/src/lib.rs
@@ -3,6 +3,7 @@
 #![feature(rustdoc_internals)]
 #![allow(internal_features)]
 #![feature(decl_macro)]
+#![feature(error_iter)]
 #![feature(extract_if)]
 #![feature(coroutines)]
 #![feature(generic_nonzero)]
@@ -39,6 +40,7 @@ pub mod errors;
 pub mod fs;
 pub mod locator;
 
+pub use creader::{load_symbol_from_dylib, DylibError};
 pub use fs::{emit_wrapper_file, METADATA_FILENAME};
 pub use native_libs::find_native_static_library;
 pub use rmeta::{encode_metadata, rendered_const, EncodedMetadata, METADATA_HEADER};
diff --git a/compiler/rustc_metadata/src/locator.rs b/compiler/rustc_metadata/src/locator.rs
index 1ab965e2876..15f56db6278 100644
--- a/compiler/rustc_metadata/src/locator.rs
+++ b/compiler/rustc_metadata/src/locator.rs
@@ -921,8 +921,8 @@ pub(crate) enum CrateError {
     MultipleCandidates(Symbol, CrateFlavor, Vec<PathBuf>),
     SymbolConflictsCurrent(Symbol),
     StableCrateIdCollision(Symbol, Symbol),
-    DlOpen(String),
-    DlSym(String),
+    DlOpen(String, String),
+    DlSym(String, String),
     LocatorCombined(Box<CombinedLocatorError>),
     NotFound(Symbol),
 }
@@ -967,8 +967,8 @@ impl CrateError {
             CrateError::StableCrateIdCollision(crate_name0, crate_name1) => {
                 dcx.emit_err(errors::StableCrateIdCollision { span, crate_name0, crate_name1 });
             }
-            CrateError::DlOpen(s) | CrateError::DlSym(s) => {
-                dcx.emit_err(errors::DlError { span, err: s });
+            CrateError::DlOpen(path, err) | CrateError::DlSym(path, err) => {
+                dcx.emit_err(errors::DlError { span, path, err });
             }
             CrateError::LocatorCombined(locator) => {
                 let crate_name = locator.crate_name;
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index cc734e7157f..9d59f779470 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -153,11 +153,6 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     ) -> Self::Const {
         Const::new_bound(self, debruijn, var, ty)
     }
-
-    fn expect_error_or_delayed_bug() {
-        let has_errors = ty::tls::with(|tcx| tcx.dcx().has_errors_or_lint_errors_or_delayed_bugs());
-        assert!(has_errors.is_some());
-    }
 }
 
 type InternedSet<'tcx, T> = ShardedHashMap<InternedInSet<'tcx, T>, ()>;
diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs
index 934e77e7deb..98fb1d8e1c9 100644
--- a/compiler/rustc_mir_transform/src/coverage/spans.rs
+++ b/compiler/rustc_mir_transform/src/coverage/spans.rs
@@ -61,7 +61,7 @@ pub(super) fn generate_coverage_spans(
             hir_info,
             basic_coverage_blocks,
         );
-        let coverage_spans = SpansRefiner::refine_sorted_spans(basic_coverage_blocks, sorted_spans);
+        let coverage_spans = SpansRefiner::refine_sorted_spans(sorted_spans);
         mappings.extend(coverage_spans.into_iter().map(|RefinedCovspan { bcb, span, .. }| {
             // Each span produced by the generator represents an ordinary code region.
             BcbMapping { kind: BcbMappingKind::Code(bcb), span }
@@ -88,8 +88,6 @@ pub(super) fn generate_coverage_spans(
 
 #[derive(Debug)]
 struct CurrCovspan {
-    /// This is used as the basis for [`PrevCovspan::original_span`], so it must
-    /// not be modified.
     span: Span,
     bcb: BasicCoverageBlock,
     is_closure: bool,
@@ -102,7 +100,7 @@ impl CurrCovspan {
 
     fn into_prev(self) -> PrevCovspan {
         let Self { span, bcb, is_closure } = self;
-        PrevCovspan { original_span: span, span, bcb, merged_spans: vec![span], is_closure }
+        PrevCovspan { span, bcb, merged_spans: vec![span], is_closure }
     }
 
     fn into_refined(self) -> RefinedCovspan {
@@ -115,7 +113,6 @@ impl CurrCovspan {
 
 #[derive(Debug)]
 struct PrevCovspan {
-    original_span: Span,
     span: Span,
     bcb: BasicCoverageBlock,
     /// List of all the original spans from MIR that have been merged into this
@@ -135,42 +132,17 @@ impl PrevCovspan {
         self.merged_spans.push(other.span);
     }
 
-    fn cutoff_statements_at(&mut self, cutoff_pos: BytePos) {
+    fn cutoff_statements_at(mut self, cutoff_pos: BytePos) -> Option<RefinedCovspan> {
         self.merged_spans.retain(|span| span.hi() <= cutoff_pos);
         if let Some(max_hi) = self.merged_spans.iter().map(|span| span.hi()).max() {
             self.span = self.span.with_hi(max_hi);
         }
-    }
-
-    fn into_dup(self) -> DuplicateCovspan {
-        let Self { original_span, span, bcb, merged_spans: _, is_closure } = self;
-        // Only unmodified spans end up in `pending_dups`.
-        debug_assert_eq!(original_span, span);
-        DuplicateCovspan { span, bcb, is_closure }
-    }
-
-    fn refined_copy(&self) -> RefinedCovspan {
-        let &Self { original_span: _, span, bcb, merged_spans: _, is_closure } = self;
-        RefinedCovspan { span, bcb, is_closure }
-    }
 
-    fn into_refined(self) -> RefinedCovspan {
-        self.refined_copy()
+        if self.merged_spans.is_empty() { None } else { Some(self.into_refined()) }
     }
-}
-
-#[derive(Debug)]
-struct DuplicateCovspan {
-    span: Span,
-    bcb: BasicCoverageBlock,
-    is_closure: bool,
-}
 
-impl DuplicateCovspan {
-    /// Returns a copy of this covspan, as a [`RefinedCovspan`].
-    /// Should only be called in places that would otherwise clone this covspan.
     fn refined_copy(&self) -> RefinedCovspan {
-        let &Self { span, bcb, is_closure } = self;
+        let &Self { span, bcb, merged_spans: _, is_closure } = self;
         RefinedCovspan { span, bcb, is_closure }
     }
 
@@ -205,10 +177,7 @@ impl RefinedCovspan {
 ///  * Merge spans that represent continuous (both in source code and control flow), non-branching
 ///    execution
 ///  * Carve out (leave uncovered) any span that will be counted by another MIR (notably, closures)
-struct SpansRefiner<'a> {
-    /// The BasicCoverageBlock Control Flow Graph (BCB CFG).
-    basic_coverage_blocks: &'a CoverageGraph,
-
+struct SpansRefiner {
     /// The initial set of coverage spans, sorted by `Span` (`lo` and `hi`) and by relative
     /// dominance between the `BasicCoverageBlock`s of equal `Span`s.
     sorted_spans_iter: std::vec::IntoIter<SpanFromMir>,
@@ -223,36 +192,22 @@ struct SpansRefiner<'a> {
     /// If that `curr` was discarded, `prev` retains its value from the previous iteration.
     some_prev: Option<PrevCovspan>,
 
-    /// One or more coverage spans with the same `Span` but different `BasicCoverageBlock`s, and
-    /// no `BasicCoverageBlock` in this list dominates another `BasicCoverageBlock` in the list.
-    /// If a new `curr` span also fits this criteria (compared to an existing list of
-    /// `pending_dups`), that `curr` moves to `prev` before possibly being added to
-    /// the `pending_dups` list, on the next iteration. As a result, if `prev` and `pending_dups`
-    /// have the same `Span`, the criteria for `pending_dups` holds for `prev` as well: a `prev`
-    /// with a matching `Span` does not dominate any `pending_dup` and no `pending_dup` dominates a
-    /// `prev` with a matching `Span`)
-    pending_dups: Vec<DuplicateCovspan>,
-
     /// The final coverage spans to add to the coverage map. A `Counter` or `Expression`
     /// will also be injected into the MIR for each BCB that has associated spans.
     refined_spans: Vec<RefinedCovspan>,
 }
 
-impl<'a> SpansRefiner<'a> {
+impl SpansRefiner {
     /// Takes the initial list of (sorted) spans extracted from MIR, and "refines"
     /// them by merging compatible adjacent spans, removing redundant spans,
     /// and carving holes in spans when they overlap in unwanted ways.
-    fn refine_sorted_spans(
-        basic_coverage_blocks: &'a CoverageGraph,
-        sorted_spans: Vec<SpanFromMir>,
-    ) -> Vec<RefinedCovspan> {
+    fn refine_sorted_spans(sorted_spans: Vec<SpanFromMir>) -> Vec<RefinedCovspan> {
+        let sorted_spans_len = sorted_spans.len();
         let this = Self {
-            basic_coverage_blocks,
             sorted_spans_iter: sorted_spans.into_iter(),
             some_curr: None,
             some_prev: None,
-            pending_dups: Vec::new(),
-            refined_spans: Vec::with_capacity(basic_coverage_blocks.num_nodes() * 2),
+            refined_spans: Vec::with_capacity(sorted_spans_len),
         };
 
         this.to_refined_spans()
@@ -292,21 +247,11 @@ impl<'a> SpansRefiner<'a> {
                 self.take_curr(); // Discards curr.
             } else if curr.is_closure {
                 self.carve_out_span_for_closure();
-            } else if prev.original_span == prev.span && prev.span == curr.span {
-                // Prev and curr have the same span, and prev's span hasn't
-                // been modified by other spans.
-                self.update_pending_dups();
             } else {
                 self.cutoff_prev_at_overlapping_curr();
             }
         }
 
-        // Drain any remaining dups into the output.
-        for dup in self.pending_dups.drain(..) {
-            debug!("    ...adding at least one pending dup={:?}", dup);
-            self.refined_spans.push(dup.into_refined());
-        }
-
         // There is usually a final span remaining in `prev` after the loop ends,
         // so add it to the output as well.
         if let Some(prev) = self.some_prev.take() {
@@ -359,36 +304,6 @@ impl<'a> SpansRefiner<'a> {
         self.some_prev.take().unwrap_or_else(|| bug!("some_prev is None (take_prev)"))
     }
 
-    /// If there are `pending_dups` but `prev` is not a matching dup (`prev.span` doesn't match the
-    /// `pending_dups` spans), then one of the following two things happened during the previous
-    /// iteration:
-    ///   * the previous `curr` span (which is now `prev`) was not a duplicate of the pending_dups
-    ///     (in which case there should be at least two spans in `pending_dups`); or
-    ///   * the `span` of `prev` was modified by `curr_mut().merge_from(prev)` (in which case
-    ///     `pending_dups` could have as few as one span)
-    /// In either case, no more spans will match the span of `pending_dups`, so
-    /// add the `pending_dups` if they don't overlap `curr`, and clear the list.
-    fn maybe_flush_pending_dups(&mut self) {
-        let Some(last_dup) = self.pending_dups.last() else { return };
-        if last_dup.span == self.prev().span {
-            return;
-        }
-
-        debug!(
-            "    SAME spans, but pending_dups are NOT THE SAME, so BCBs matched on \
-            previous iteration, or prev started a new disjoint span"
-        );
-        if last_dup.span.hi() <= self.curr().span.lo() {
-            for dup in self.pending_dups.drain(..) {
-                debug!("    ...adding at least one pending={:?}", dup);
-                self.refined_spans.push(dup.into_refined());
-            }
-        } else {
-            self.pending_dups.clear();
-        }
-        assert!(self.pending_dups.is_empty());
-    }
-
     /// Advance `prev` to `curr` (if any), and `curr` to the next coverage span in sorted order.
     fn next_coverage_span(&mut self) -> bool {
         if let Some(curr) = self.some_curr.take() {
@@ -408,7 +323,6 @@ impl<'a> SpansRefiner<'a> {
                 );
             } else {
                 self.some_curr = Some(CurrCovspan::new(curr.span, curr.bcb, curr.is_closure));
-                self.maybe_flush_pending_dups();
                 return true;
             }
         }
@@ -433,13 +347,6 @@ impl<'a> SpansRefiner<'a> {
             let mut pre_closure = self.prev().refined_copy();
             pre_closure.span = pre_closure.span.with_hi(left_cutoff);
             debug!("  prev overlaps a closure. Adding span for pre_closure={:?}", pre_closure);
-
-            for mut dup in self.pending_dups.iter().map(DuplicateCovspan::refined_copy) {
-                dup.span = dup.span.with_hi(left_cutoff);
-                debug!("    ...and at least one pre_closure dup={:?}", dup);
-                self.refined_spans.push(dup);
-            }
-
             self.refined_spans.push(pre_closure);
         }
 
@@ -448,58 +355,9 @@ impl<'a> SpansRefiner<'a> {
             self.prev_mut().span = self.prev().span.with_lo(right_cutoff);
             debug!("  Mutated prev.span to start after the closure. prev={:?}", self.prev());
 
-            for dup in &mut self.pending_dups {
-                debug!("    ...and at least one overlapping dup={:?}", dup);
-                dup.span = dup.span.with_lo(right_cutoff);
-            }
-
             // Prevent this curr from becoming prev.
             let closure_covspan = self.take_curr().into_refined();
             self.refined_spans.push(closure_covspan); // since self.prev() was already updated
-        } else {
-            self.pending_dups.clear();
-        }
-    }
-
-    /// Called if `curr.span` equals `prev.original_span` (and potentially equal to all
-    /// `pending_dups` spans, if any). Keep in mind, `prev.span()` may have been changed.
-    /// If prev.span() was merged into other spans (with matching BCB, for instance),
-    /// `prev.span.hi()` will be greater than (further right of) `prev.original_span.hi()`.
-    /// If prev.span() was split off to the right of a closure, prev.span().lo() will be
-    /// greater than prev.original_span.lo(). The actual span of `prev.original_span` is
-    /// not as important as knowing that `prev()` **used to have the same span** as `curr()`,
-    /// which means their sort order is still meaningful for determining the dominator
-    /// relationship.
-    ///
-    /// When two coverage spans have the same `Span`, dominated spans can be discarded; but if
-    /// neither coverage span dominates the other, both (or possibly more than two) are held,
-    /// until their disposition is determined. In this latter case, the `prev` dup is moved into
-    /// `pending_dups` so the new `curr` dup can be moved to `prev` for the next iteration.
-    fn update_pending_dups(&mut self) {
-        let prev_bcb = self.prev().bcb;
-        let curr_bcb = self.curr().bcb;
-
-        // Equal coverage spans are ordered by dominators before dominated (if any), so it should be
-        // impossible for `curr` to dominate any previous coverage span.
-        debug_assert!(!self.basic_coverage_blocks.dominates(curr_bcb, prev_bcb));
-
-        // `prev` is a duplicate of `curr`, so add it to the list of pending dups.
-        // If it dominates `curr`, it will be removed by the subsequent discard step.
-        let prev = self.take_prev().into_dup();
-        debug!(?prev, "adding prev to pending dups");
-        self.pending_dups.push(prev);
-
-        let initial_pending_count = self.pending_dups.len();
-        if initial_pending_count > 0 {
-            self.pending_dups
-                .retain(|dup| !self.basic_coverage_blocks.dominates(dup.bcb, curr_bcb));
-
-            let n_discarded = initial_pending_count - self.pending_dups.len();
-            if n_discarded > 0 {
-                debug!(
-                    "  discarded {n_discarded} of {initial_pending_count} pending_dups that dominated curr",
-                );
-            }
         }
     }
 
@@ -516,19 +374,13 @@ impl<'a> SpansRefiner<'a> {
             if it has statements that end before curr; prev={:?}",
             self.prev()
         );
-        if self.pending_dups.is_empty() {
-            let curr_span = self.curr().span;
-            self.prev_mut().cutoff_statements_at(curr_span.lo());
-            if self.prev().merged_spans.is_empty() {
-                debug!("  ... no non-overlapping statements to add");
-            } else {
-                debug!("  ... adding modified prev={:?}", self.prev());
-                let prev = self.take_prev().into_refined();
-                self.refined_spans.push(prev);
-            }
+
+        let curr_span = self.curr().span;
+        if let Some(prev) = self.take_prev().cutoff_statements_at(curr_span.lo()) {
+            debug!("after cutoff, adding {prev:?}");
+            self.refined_spans.push(prev);
         } else {
-            // with `pending_dups`, `prev` cannot have any statements that don't overlap
-            self.pending_dups.clear();
+            debug!("prev was eliminated by cutoff");
         }
     }
 }
diff --git a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
index 2db358379fe..b91ab811918 100644
--- a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
+++ b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
@@ -52,14 +52,19 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
             // - Span A extends further left, or
             // - Both have the same start and span A extends further right
             .then_with(|| Ord::cmp(&a.span.hi(), &b.span.hi()).reverse())
-            // If both spans are equal, sort the BCBs in dominator order,
-            // so that dominating BCBs come before other BCBs they dominate.
-            .then_with(|| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb))
-            // If two spans are otherwise identical, put closure spans first,
-            // as this seems to be what the refinement step expects.
+            // If two spans have the same lo & hi, put closure spans first,
+            // as they take precedence over non-closure spans.
             .then_with(|| Ord::cmp(&a.is_closure, &b.is_closure).reverse())
+            // After deduplication, we want to keep only the most-dominated BCB.
+            .then_with(|| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb).reverse())
     });
 
+    // Among covspans with the same span, keep only one. Closure spans take
+    // precedence, otherwise keep the one with the most-dominated BCB.
+    // (Ideally we should try to preserve _all_ non-dominating BCBs, but that
+    // requires a lot more complexity in the span refiner, for little benefit.)
+    initial_spans.dedup_by(|b, a| a.span.source_equal(b.span));
+
     initial_spans
 }
 
diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index 486396b0677..a3106856a67 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -237,7 +237,10 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
     ) {
         let variant = match self.typeck_results().node_type(lhs.hir_id).kind() {
             ty::Adt(adt, _) => adt.variant_of_res(res),
-            _ => span_bug!(lhs.span, "non-ADT in tuple struct pattern"),
+            _ => {
+                self.tcx.dcx().span_delayed_bug(lhs.span, "non-ADT in tuple struct pattern");
+                return;
+            }
         };
         let dotdot = dotdot.as_opt_usize().unwrap_or(pats.len());
         let first_n = pats.iter().enumerate().take(dotdot);
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index 3a8dc377520..487407014d1 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -526,8 +526,8 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
     }
 
     fn define_bindings_in_pat(&mut self, pat: &hir::Pat<'_>, mut succ: LiveNode) -> LiveNode {
-        // In an or-pattern, only consider the first pattern; any later patterns
-        // must have the same bindings, and we also consider the first pattern
+        // In an or-pattern, only consider the first non-never pattern; any later patterns
+        // must have the same bindings, and we also consider that pattern
         // to be the "authoritative" set of ids.
         pat.each_binding_or_first(&mut |_, hir_id, pat_sp, ident| {
             let ln = self.live_node(hir_id, pat_sp);
diff --git a/compiler/rustc_query_system/src/dep_graph/graph.rs b/compiler/rustc_query_system/src/dep_graph/graph.rs
index b6ac54a9ab5..7dc1a1f7917 100644
--- a/compiler/rustc_query_system/src/dep_graph/graph.rs
+++ b/compiler/rustc_query_system/src/dep_graph/graph.rs
@@ -817,7 +817,7 @@ impl<D: Deps> DepGraphData<D> {
             None => {}
         }
 
-        if let None = qcx.dep_context().sess().dcx().has_errors_or_lint_errors_or_delayed_bugs() {
+        if let None = qcx.dep_context().sess().dcx().has_errors_or_delayed_bugs() {
             panic!("try_mark_previous_green() - Forcing the DepNode should have set its color")
         }
 
diff --git a/compiler/rustc_session/src/output.rs b/compiler/rustc_session/src/output.rs
index db976b30404..74d26237f24 100644
--- a/compiler/rustc_session/src/output.rs
+++ b/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();
     }
 }
 
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 9d1133c487f..02c7a0c6371 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -258,7 +258,8 @@ impl Session {
         }
     }
 
-    fn check_miri_unleashed_features(&self) {
+    fn check_miri_unleashed_features(&self) -> Option<ErrorGuaranteed> {
+        let mut guar = None;
         let unleashed_features = self.miri_unleashed_features.lock();
         if !unleashed_features.is_empty() {
             let mut must_err = false;
@@ -279,18 +280,22 @@ impl Session {
             // If we should err, make sure we did.
             if must_err && self.dcx().has_errors().is_none() {
                 // We have skipped a feature gate, and not run into other errors... reject.
-                self.dcx().emit_err(errors::NotCircumventFeature);
+                guar = Some(self.dcx().emit_err(errors::NotCircumventFeature));
             }
         }
+        guar
     }
 
     /// Invoked all the way at the end to finish off diagnostics printing.
-    pub fn finish_diagnostics(&self, registry: &Registry) {
-        self.check_miri_unleashed_features();
+    pub fn finish_diagnostics(&self, registry: &Registry) -> Option<ErrorGuaranteed> {
+        let mut guar = None;
+        guar = guar.or(self.check_miri_unleashed_features());
+        guar = guar.or(self.dcx().emit_stashed_diagnostics());
         self.dcx().print_error_count(registry);
         if self.opts.json_future_incompat {
             self.dcx().emit_future_breakage_report();
         }
+        guar
     }
 
     /// Returns true if the crate is a testing one.
@@ -312,16 +317,6 @@ impl Session {
         err
     }
 
-    pub fn compile_status(&self) -> Result<(), ErrorGuaranteed> {
-        // We must include lint errors here.
-        if let Some(reported) = self.dcx().has_errors_or_lint_errors() {
-            self.dcx().emit_stashed_diagnostics();
-            Err(reported)
-        } else {
-            Ok(())
-        }
-    }
-
     /// Record the fact that we called `trimmed_def_paths`, and do some
     /// checking about whether its cost was justified.
     pub fn record_trimmed_def_paths(&self) {
@@ -1410,10 +1405,6 @@ impl EarlyDiagCtxt {
         Self { dcx: DiagCtxt::with_emitter(emitter) }
     }
 
-    pub fn abort_if_errors(&self) {
-        self.dcx.abort_if_errors()
-    }
-
     /// Swap out the underlying dcx once we acquire the user's preference on error emission
     /// format. Any errors prior to that will cause an abort and all stashed diagnostics of the
     /// previous dcx will be emitted.
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index aa8bd5fdc86..7186b96b40d 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/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();
-
-        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!"
-        );
+        FatalError.raise();
     }
 
     fn build_overflow_error<T>(
diff --git a/compiler/rustc_type_ir/src/interner.rs b/compiler/rustc_type_ir/src/interner.rs
index 7728ee0e842..7d2c42a6dbe 100644
--- a/compiler/rustc_type_ir/src/interner.rs
+++ b/compiler/rustc_type_ir/src/interner.rs
@@ -95,9 +95,6 @@ pub trait Interner: Sized {
     fn mk_bound_ty(self, debruijn: DebruijnIndex, var: BoundVar) -> Self::Ty;
     fn mk_bound_region(self, debruijn: DebruijnIndex, var: BoundVar) -> Self::Region;
     fn mk_bound_const(self, debruijn: DebruijnIndex, var: BoundVar, ty: Self::Ty) -> Self::Const;
-
-    /// Assert that an error has been delayed or emitted.
-    fn expect_error_or_delayed_bug();
 }
 
 /// Common capabilities of placeholder kinds