Auto merge of rust-lang#121129 - nnethercote:codegen-Diags, r=estebank

Improve codegen diagnostic handling

Clarify the workings of the temporary `Diagnostic` type used to send diagnostics from codegen threads to the main thread.

r? `@estebank`

compiler/rustc_codegen_llvm/src/errors.rs

@@ -103,8 +103,7 @@ impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for ParseTargetMachineConfig<'_
     fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> DiagnosticBuilder<'_, G> {
         let diag: DiagnosticBuilder<'_, G> = self.0.into_diagnostic(dcx, level);
         let (message, _) = diag.messages.first().expect("`LlvmError` with no message");
-        let message = dcx.eagerly_translate_to_string(message.clone(), diag.args());
-
+        let message = dcx.eagerly_translate_to_string(message.clone(), diag.args.iter());
         DiagnosticBuilder::new(dcx, level, fluent::codegen_llvm_parse_target_machine_config)
             .with_arg("error", message)
     }

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -16,8 +16,8 @@ use rustc_data_structures::sync::Lrc;
 use rustc_errors::emitter::Emitter;
 use rustc_errors::translation::Translate;
 use rustc_errors::{
-    DiagCtxt, DiagnosticArgName, DiagnosticArgValue, DiagnosticBuilder, DiagnosticMessage, ErrCode,
-    FatalError, FluentBundle, Level, Style,
+    DiagCtxt, DiagnosticArgMap, DiagnosticBuilder, DiagnosticMessage, ErrCode, FatalError,
+    FluentBundle, Level, MultiSpan, Style,
 };
 use rustc_fs_util::link_or_copy;
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
@@ -999,11 +999,29 @@ pub(crate) enum Message<B: WriteBackendMethods> {
 /// process another codegen unit.
 pub struct CguMessage;
 
+// A cut-down version of `rustc_errors::Diagnostic` that impls `Send`, which
+// can be used to send diagnostics from codegen threads to the main thread.
+// It's missing the following fields from `rustc_errors::Diagnostic`.
+// - `span`: it doesn't impl `Send`.
+// - `suggestions`: it doesn't impl `Send`, and isn't used for codegen
+//   diagnostics.
+// - `sort_span`: it doesn't impl `Send`.
+// - `is_lint`: lints aren't relevant during codegen.
+// - `emitted_at`: not used for codegen diagnostics.
 struct Diagnostic {
-    msgs: Vec<(DiagnosticMessage, Style)>,
-    args: FxIndexMap<DiagnosticArgName, DiagnosticArgValue>,
+    level: Level,
+    messages: Vec<(DiagnosticMessage, Style)>,
     code: Option<ErrCode>,
-    lvl: Level,
+    children: Vec<Subdiagnostic>,
+    args: DiagnosticArgMap,
+}
+
+// A cut-down version of `rustc_errors::SubDiagnostic` that impls `Send`. It's
+// missing the following fields from `rustc_errors::SubDiagnostic`.
+// - `span`: it doesn't impl `Send`.
+pub struct Subdiagnostic {
+    level: Level,
+    messages: Vec<(DiagnosticMessage, Style)>,
 }
 
 #[derive(PartialEq, Clone, Copy, Debug)]
@@ -1766,7 +1784,6 @@ fn spawn_work<'a, B: ExtraBackendMethods>(
 enum SharedEmitterMessage {
     Diagnostic(Diagnostic),
     InlineAsmError(u32, String, Level, Option<(String, Vec<InnerSpan>)>),
-    AbortIfErrors,
     Fatal(String),
 }
 
@@ -1812,24 +1829,29 @@ impl Translate for SharedEmitter {
 }
 
 impl Emitter for SharedEmitter {
-    fn emit_diagnostic(&mut self, diag: rustc_errors::Diagnostic) {
-        let args: FxIndexMap<DiagnosticArgName, DiagnosticArgValue> =
-            diag.args().map(|(name, arg)| (name.clone(), arg.clone())).collect();
-        drop(self.sender.send(SharedEmitterMessage::Diagnostic(Diagnostic {
-            msgs: diag.messages.clone(),
-            args: args.clone(),
-            code: diag.code,
-            lvl: diag.level(),
-        })));
-        for child in &diag.children {
-            drop(self.sender.send(SharedEmitterMessage::Diagnostic(Diagnostic {
-                msgs: child.messages.clone(),
-                args: args.clone(),
-                code: None,
-                lvl: child.level,
-            })));
-        }
-        drop(self.sender.send(SharedEmitterMessage::AbortIfErrors));
+    fn emit_diagnostic(&mut self, mut diag: rustc_errors::Diagnostic) {
+        // Check that we aren't missing anything interesting when converting to
+        // the cut-down local `Diagnostic`.
+        assert_eq!(diag.span, MultiSpan::new());
+        assert_eq!(diag.suggestions, Ok(vec![]));
+        assert_eq!(diag.sort_span, rustc_span::DUMMY_SP);
+        assert_eq!(diag.is_lint, None);
+        // No sensible check for `diag.emitted_at`.
+
+        let args = mem::replace(&mut diag.args, DiagnosticArgMap::default());
+        drop(
+            self.sender.send(SharedEmitterMessage::Diagnostic(Diagnostic {
+                level: diag.level(),
+                messages: diag.messages,
+                code: diag.code,
+                children: diag
+                    .children
+                    .into_iter()
+                    .map(|child| Subdiagnostic { level: child.level, messages: child.messages })
+                    .collect(),
+                args,
+            })),
+        );
     }
 
     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
@@ -1854,11 +1876,24 @@ impl SharedEmitterMain {
 
             match message {
                 Ok(SharedEmitterMessage::Diagnostic(diag)) => {
+                    // The diagnostic has been received on the main thread.
+                    // Convert it back to a full `Diagnostic` and emit.
                     let dcx = sess.dcx();
-                    let mut d = rustc_errors::Diagnostic::new_with_messages(diag.lvl, diag.msgs);
+                    let mut d =
+                        rustc_errors::Diagnostic::new_with_messages(diag.level, diag.messages);
                     d.code = diag.code; // may be `None`, that's ok
-                    d.replace_args(diag.args);
+                    d.children = diag
+                        .children
+                        .into_iter()
+                        .map(|sub| rustc_errors::SubDiagnostic {
+                            level: sub.level,
+                            messages: sub.messages,
+                            span: MultiSpan::new(),
+                        })
+                        .collect();
+                    d.args = diag.args;
                     dcx.emit_diagnostic(d);
+                    sess.dcx().abort_if_errors();
                 }
                 Ok(SharedEmitterMessage::InlineAsmError(cookie, msg, level, source)) => {
                     assert!(matches!(level, Level::Error | Level::Warning | Level::Note));
@@ -1891,9 +1926,6 @@ impl SharedEmitterMain {
 
                     err.emit();
                 }
-                Ok(SharedEmitterMessage::AbortIfErrors) => {
-                    sess.dcx().abort_if_errors();
-                }
                 Ok(SharedEmitterMessage::Fatal(msg)) => {
                     sess.dcx().fatal(msg);
                 }

compiler/rustc_const_eval/src/errors.rs

@@ -437,7 +437,7 @@ pub trait ReportErrorExt {
             let mut diag = dcx.struct_allow(DiagnosticMessage::Str(String::new().into()));
             let message = self.diagnostic_message();
             self.add_args(&mut diag);
-            let s = dcx.eagerly_translate_to_string(message, diag.args());
+            let s = dcx.eagerly_translate_to_string(message, diag.args.iter());
             diag.cancel();
             s
         })
@@ -864,7 +864,7 @@ impl<'tcx> ReportErrorExt for InvalidProgramInfo<'tcx> {
                 let dummy_level = Level::Bug;
                 let dummy_diag: DiagnosticBuilder<'_, ()> =
                     e.into_diagnostic().into_diagnostic(diag.dcx, dummy_level);
-                for (name, val) in dummy_diag.args() {
+                for (name, val) in dummy_diag.args.iter() {
                     diag.arg(name.clone(), val.clone());
                 }
                 dummy_diag.cancel();

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -446,7 +446,7 @@ pub fn format_interp_error<'tcx>(dcx: &DiagCtxt, e: InterpErrorInfo<'tcx>) -> St
     let mut diag = dcx.struct_allow("");
     let msg = e.diagnostic_message();
     e.add_args(&mut diag);
-    let s = dcx.eagerly_translate_to_string(msg, diag.args());
+    let s = dcx.eagerly_translate_to_string(msg, diag.args.iter());
     diag.cancel();
     s
 }

compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs

@@ -45,7 +45,7 @@ impl Translate for AnnotateSnippetEmitter {
 impl Emitter for AnnotateSnippetEmitter {
     /// The entry point for the diagnostics generation
     fn emit_diagnostic(&mut self, mut diag: Diagnostic) {
-        let fluent_args = to_fluent_args(diag.args());
+        let fluent_args = to_fluent_args(diag.args.iter());
 
         let mut suggestions = diag.suggestions.unwrap_or(vec![]);
         self.primary_span_formatted(&mut diag.span, &mut suggestions, &fluent_args);

compiler/rustc_errors/src/diagnostic.rs

@@ -43,6 +43,8 @@ pub enum DiagnosticArgValue {
     StrListSepByAnd(Vec<Cow<'static, str>>),
 }
 
+pub type DiagnosticArgMap = FxIndexMap<DiagnosticArgName, DiagnosticArgValue>;
+
 /// Trait for types that `DiagnosticBuilder::emit` can return as a "guarantee"
 /// (or "proof") token that the emission happened.
 pub trait EmissionGuarantee: Sized {
@@ -275,7 +277,7 @@ pub struct Diagnostic {
     pub span: MultiSpan,
     pub children: Vec<SubDiagnostic>,
     pub suggestions: Result<Vec<CodeSuggestion>, SuggestionsDisabled>,
-    args: FxIndexMap<DiagnosticArgName, DiagnosticArgValue>,
+    pub args: DiagnosticArgMap,
 
     /// This is not used for highlighting or rendering any error message. Rather, it can be used
     /// as a sort key to sort a buffer of diagnostics. By default, it is the primary span of
@@ -403,14 +405,6 @@ impl Diagnostic {
         self.args.insert(name.into(), arg.into_diagnostic_arg());
     }
 
-    pub fn args(&self) -> impl Iterator<Item = DiagnosticArg<'_>> {
-        self.args.iter()
-    }
-
-    pub fn replace_args(&mut self, args: FxIndexMap<DiagnosticArgName, DiagnosticArgValue>) {
-        self.args = args;
-    }
-
     /// Fields used for Hash, and PartialEq trait.
     fn keys(
         &self,
@@ -431,7 +425,7 @@ impl Diagnostic {
             &self.span,
             &self.children,
             &self.suggestions,
-            self.args().collect(),
+            self.args.iter().collect(),
             // omit self.sort_span
             &self.is_lint,
             // omit self.emitted_at
@@ -1165,7 +1159,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
         subdiagnostic: impl AddToDiagnostic,
     ) -> &mut Self {
         subdiagnostic.add_to_diagnostic_with(self, |diag, msg| {
-            let args = diag.args();
+            let args = diag.args.iter();
             let msg = diag.subdiagnostic_message_to_diagnostic_message(msg);
             dcx.eagerly_translate(msg, args)
         });

compiler/rustc_errors/src/emitter.rs

@@ -519,7 +519,7 @@ impl Emitter for HumanEmitter {
     }
 
     fn emit_diagnostic(&mut self, mut diag: Diagnostic) {
-        let fluent_args = to_fluent_args(diag.args());
+        let fluent_args = to_fluent_args(diag.args.iter());
 
         let mut suggestions = diag.suggestions.unwrap_or(vec![]);
         self.primary_span_formatted(&mut diag.span, &mut suggestions, &fluent_args);

compiler/rustc_errors/src/json.rs

@@ -341,7 +341,7 @@ struct UnusedExterns<'a, 'b, 'c> {
 
 impl Diagnostic {
     fn from_errors_diagnostic(diag: crate::Diagnostic, je: &JsonEmitter) -> Diagnostic {
-        let args = to_fluent_args(diag.args());
+        let args = to_fluent_args(diag.args.iter());
         let sugg = diag.suggestions.iter().flatten().map(|sugg| {
             let translated_message =
                 je.translate_message(&sugg.msg, &args).map_err(Report::new).unwrap();

compiler/rustc_errors/src/lib.rs

@@ -37,9 +37,10 @@ extern crate self as rustc_errors;
 
 pub use codes::*;
 pub use diagnostic::{
-    AddToDiagnostic, BugAbort, DecorateLint, Diagnostic, DiagnosticArg, DiagnosticArgName,
-    DiagnosticArgValue, DiagnosticBuilder, DiagnosticStyledString, EmissionGuarantee, FatalAbort,
-    IntoDiagnostic, IntoDiagnosticArg, StringPart, SubDiagnostic, SubdiagnosticMessageOp,
+    AddToDiagnostic, BugAbort, DecorateLint, Diagnostic, DiagnosticArg, DiagnosticArgMap,
+    DiagnosticArgName, DiagnosticArgValue, DiagnosticBuilder, DiagnosticStyledString,
+    EmissionGuarantee, FatalAbort, IntoDiagnostic, IntoDiagnosticArg, StringPart, SubDiagnostic,
+    SubdiagnosticMessageOp,
 };
 pub use diagnostic_impls::{
     DiagnosticArgFromDisplay, DiagnosticSymbolList, ExpectedLifetimeParameter,
@@ -1496,9 +1497,8 @@ impl DiagCtxtInner {
         diag: &Diagnostic,
         msg: impl Into<SubdiagnosticMessage>,
     ) -> SubdiagnosticMessage {
-        let args = diag.args();
         let msg = diag.subdiagnostic_message_to_diagnostic_message(msg);
-        self.eagerly_translate(msg, args)
+        self.eagerly_translate(msg, diag.args.iter())
     }
 
     fn flush_delayed(&mut self) {

src/librustdoc/passes/lint/check_code_block_syntax.rs

@@ -159,7 +159,7 @@ impl Emitter for BufferEmitter {
     fn emit_diagnostic(&mut self, diag: Diagnostic) {
         let mut buffer = self.buffer.borrow_mut();
 
-        let fluent_args = to_fluent_args(diag.args());
+        let fluent_args = to_fluent_args(diag.args.iter());
         let translated_main_message = self
             .translate_message(&diag.messages[0].0, &fluent_args)
             .unwrap_or_else(|e| panic!("{e}"));

tests/ui/lto/issue-11154.stderr

@@ -1,6 +1,6 @@
 error: cannot prefer dynamic linking when performing LTO
-
-note: only 'staticlib', 'bin', and 'cdylib' outputs are supported with LTO
+   |
+   = note: only 'staticlib', 'bin', and 'cdylib' outputs are supported with LTO
 
 error: aborting due to 1 previous error