errors: share SilentEmitter between rustc and rustfmt

Signed-off-by: David Wood <david@davidtw.co>

compiler/rustc_errors/src/emitter.rs

@@ -10,7 +10,6 @@
 use rustc_span::source_map::SourceMap;
 use rustc_span::{FileLines, FileName, SourceFile, Span};
 
-use crate::error::TranslateError;
 use crate::snippet::{
     Annotation, AnnotationColumn, AnnotationType, Line, MultilineAnnotation, Style, StyledString,
 };
@@ -539,20 +538,9 @@ impl Emitter for HumanEmitter {
 /// Fatal diagnostics are forwarded to `fatal_dcx` to avoid silent
 /// failures of rustc, as witnessed e.g. in issue #89358.
 pub struct SilentEmitter {
+    pub fallback_bundle: LazyFallbackBundle,
     pub fatal_dcx: DiagCtxt,
-    pub fatal_note: String,
-}
-
-pub fn silent_translate<'a>(
-    message: &'a DiagnosticMessage,
-) -> Result<Cow<'_, str>, TranslateError<'_>> {
-    match message {
-        DiagnosticMessage::Str(msg) | DiagnosticMessage::Translated(msg) => Ok(Cow::Borrowed(msg)),
-        DiagnosticMessage::FluentIdentifier(identifier, _) => {
-            // Any value works here.
-            Ok(identifier.clone())
-        }
-    }
+    pub fatal_note: Option<String>,
 }
 
 impl Translate for SilentEmitter {
@@ -561,17 +549,9 @@ impl Translate for SilentEmitter {
     }
 
     fn fallback_fluent_bundle(&self) -> &FluentBundle {
-        panic!("silent emitter attempted to translate message")
-    }
-
-    // Override `translate_message` for the silent emitter because eager translation of
-    // subdiagnostics result in a call to this.
-    fn translate_message<'a>(
-        &'a self,
-        message: &'a DiagnosticMessage,
-        _: &'a FluentArgs<'_>,
-    ) -> Result<Cow<'_, str>, TranslateError<'_>> {
-        silent_translate(message)
+        // Ideally this field wouldn't be necessary and the fallback bundle in `fatal_dcx` would be
+        // used but the lock prevents this.
+        &self.fallback_bundle
     }
 }
 
@@ -582,7 +562,9 @@ impl Emitter for SilentEmitter {
 
     fn emit_diagnostic(&mut self, mut diag: DiagInner) {
         if diag.level == Level::Fatal {
-            diag.sub(Level::Note, self.fatal_note.clone(), MultiSpan::new());
+            if let Some(fatal_note) = &self.fatal_note {
+                diag.sub(Level::Note, fatal_note.clone(), MultiSpan::new());
+            }
             self.fatal_dcx.emit_diagnostic(diag);
         }
     }

compiler/rustc_errors/src/lib.rs

@@ -63,7 +63,7 @@ use emitter::{is_case_difference, DynEmitter, Emitter};
 use registry::Registry;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::stable_hasher::{Hash128, StableHasher};
-use rustc_data_structures::sync::Lock;
+use rustc_data_structures::sync::{Lock, Lrc};
 use rustc_data_structures::AtomicRef;
 use rustc_lint_defs::LintExpectationId;
 use rustc_span::source_map::SourceMap;
@@ -606,29 +606,54 @@ impl DiagCtxt {
     }
 
     pub fn new(emitter: Box<DynEmitter>) -> Self {
-        Self {
-            inner: Lock::new(DiagCtxtInner {
-                flags: DiagCtxtFlags { can_emit_warnings: true, ..Default::default() },
-                err_guars: Vec::new(),
-                lint_err_guars: Vec::new(),
-                delayed_bugs: Vec::new(),
-                deduplicated_err_count: 0,
-                deduplicated_warn_count: 0,
-                emitter,
-                must_produce_diag: false,
-                has_printed: false,
-                suppressed_expected_diag: false,
-                taught_diagnostics: Default::default(),
-                emitted_diagnostic_codes: Default::default(),
-                emitted_diagnostics: Default::default(),
-                stashed_diagnostics: Default::default(),
-                future_breakage_diagnostics: Vec::new(),
-                check_unstable_expect_diagnostics: false,
-                unstable_expect_diagnostics: Vec::new(),
-                fulfilled_expectations: Default::default(),
-                ice_file: None,
-            }),
+        Self { inner: Lock::new(DiagCtxtInner::new(emitter)) }
+    }
+
+    pub fn make_silent(&mut self, fallback_bundle: LazyFallbackBundle, fatal_note: Option<String>) {
+        self.wrap_emitter(|old_dcx| {
+            Box::new(emitter::SilentEmitter {
+                fallback_bundle,
+                fatal_dcx: DiagCtxt { inner: Lock::new(old_dcx) },
+                fatal_note,
+            })
+        });
+    }
+
+    fn wrap_emitter<F>(&mut self, f: F)
+    where
+        F: FnOnce(DiagCtxtInner) -> Box<DynEmitter>,
+    {
+        // A empty type that implements `Emitter` so that a `DiagCtxtInner` can be constructed
+        // to temporarily swap in place of the real one, which will be used in constructing
+        // its replacement.
+        struct FalseEmitter;
+
+        impl Emitter for FalseEmitter {
+            fn emit_diagnostic(&mut self, _: DiagInner) {
+                unimplemented!("false emitter must only used during `wrap_emitter`")
+            }
+
+            fn source_map(&self) -> Option<&Lrc<SourceMap>> {
+                unimplemented!("false emitter must only used during `wrap_emitter`")
+            }
         }
+
+        impl translation::Translate for FalseEmitter {
+            fn fluent_bundle(&self) -> Option<&Lrc<FluentBundle>> {
+                unimplemented!("false emitter must only used during `wrap_emitter`")
+            }
+
+            fn fallback_fluent_bundle(&self) -> &FluentBundle {
+                unimplemented!("false emitter must only used during `wrap_emitter`")
+            }
+        }
+
+        let mut inner = self.inner.borrow_mut();
+        let mut prev_dcx = DiagCtxtInner::new(Box::new(FalseEmitter));
+        std::mem::swap(&mut *inner, &mut prev_dcx);
+        let new_emitter = f(prev_dcx);
+        let mut new_dcx = DiagCtxtInner::new(new_emitter);
+        std::mem::swap(&mut *inner, &mut new_dcx);
     }
 
     /// Translate `message` eagerly with `args` to `SubdiagnosticMessage::Eager`.
@@ -1345,6 +1370,30 @@ impl DiagCtxt {
 // `DiagCtxt::foo()` just borrows `inner` and forwards a call to
 // `DiagCtxtInner::foo`.
 impl DiagCtxtInner {
+    fn new(emitter: Box<DynEmitter>) -> Self {
+        Self {
+            flags: DiagCtxtFlags { can_emit_warnings: true, ..Default::default() },
+            err_guars: Vec::new(),
+            lint_err_guars: Vec::new(),
+            delayed_bugs: Vec::new(),
+            deduplicated_err_count: 0,
+            deduplicated_warn_count: 0,
+            emitter,
+            must_produce_diag: false,
+            has_printed: false,
+            suppressed_expected_diag: false,
+            taught_diagnostics: Default::default(),
+            emitted_diagnostic_codes: Default::default(),
+            emitted_diagnostics: Default::default(),
+            stashed_diagnostics: Default::default(),
+            future_breakage_diagnostics: Vec::new(),
+            check_unstable_expect_diagnostics: false,
+            unstable_expect_diagnostics: Vec::new(),
+            fulfilled_expectations: Default::default(),
+            ice_file: None,
+        }
+    }
+
     /// Emit all stashed diagnostics.
     fn emit_stashed_diagnostics(&mut self) -> Option<ErrorGuaranteed> {
         let mut guar = None;

compiler/rustc_interface/src/interface.rs

@@ -45,9 +45,10 @@ pub struct Compiler {
 pub(crate) fn parse_cfg(dcx: &DiagCtxt, cfgs: Vec<String>) -> Cfg {
     cfgs.into_iter()
         .map(|s| {
-            let sess = ParseSess::with_silent_emitter(format!(
-                "this error occurred on the command line: `--cfg={s}`"
-            ));
+            let sess = ParseSess::with_silent_emitter(
+                vec![crate::DEFAULT_LOCALE_RESOURCE, rustc_parse::DEFAULT_LOCALE_RESOURCE],
+                format!("this error occurred on the command line: `--cfg={s}`"),
+            );
             let filename = FileName::cfg_spec_source_code(&s);
 
             macro_rules! error {
@@ -107,9 +108,10 @@ pub(crate) fn parse_check_cfg(dcx: &DiagCtxt, specs: Vec<String>) -> CheckCfg {
     let mut check_cfg = CheckCfg { exhaustive_names, exhaustive_values, ..CheckCfg::default() };
 
     for s in specs {
-        let sess = ParseSess::with_silent_emitter(format!(
-            "this error occurred on the command line: `--check-cfg={s}`"
-        ));
+        let sess = ParseSess::with_silent_emitter(
+            vec![crate::DEFAULT_LOCALE_RESOURCE, rustc_parse::DEFAULT_LOCALE_RESOURCE],
+            format!("this error occurred on the command line: `--check-cfg={s}`"),
+        );
         let filename = FileName::cfg_spec_source_code(&s);
 
         macro_rules! error {

compiler/rustc_session/src/parse.rs

@@ -266,14 +266,20 @@ impl ParseSess {
         }
     }
 
-    pub fn with_silent_emitter(fatal_note: String) -> Self {
-        let fallback_bundle = fallback_fluent_bundle(Vec::new(), false);
+    pub fn with_silent_emitter(locale_resources: Vec<&'static str>, fatal_note: String) -> Self {
+        let fallback_bundle = fallback_fluent_bundle(locale_resources, false);
         let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-        let emitter =
-            Box::new(HumanEmitter::new(stderr_destination(ColorConfig::Auto), fallback_bundle));
+        let emitter = Box::new(HumanEmitter::new(
+            stderr_destination(ColorConfig::Auto),
+            fallback_bundle.clone(),
+        ));
         let fatal_dcx = DiagCtxt::new(emitter);
-        let dcx =
-            DiagCtxt::new(Box::new(SilentEmitter { fatal_dcx, fatal_note })).disable_warnings();
+        let dcx = DiagCtxt::new(Box::new(SilentEmitter {
+            fallback_bundle,
+            fatal_dcx,
+            fatal_note: Some(fatal_note),
+        }))
+        .disable_warnings();
         ParseSess::with_dcx(dcx, sm)
     }
 

src/tools/rustfmt/src/parse/session.rs

@@ -1,9 +1,8 @@
-use std::borrow::Cow;
 use std::path::Path;
 use std::sync::atomic::{AtomicBool, Ordering};
 
 use rustc_data_structures::sync::{IntoDynSyncSend, Lrc};
-use rustc_errors::emitter::{stderr_destination, DynEmitter, Emitter, HumanEmitter};
+use rustc_errors::emitter::{stderr_destination, DynEmitter, Emitter, HumanEmitter, SilentEmitter};
 use rustc_errors::translation::Translate;
 use rustc_errors::{ColorConfig, Diag, DiagCtxt, DiagInner, Level as DiagnosticLevel};
 use rustc_session::parse::ParseSess as RawParseSess;
@@ -28,41 +27,6 @@ pub(crate) struct ParseSess {
     can_reset_errors: Lrc<AtomicBool>,
 }
 
-/// Emitter which discards every error.
-struct SilentEmitter;
-
-impl Translate for SilentEmitter {
-    fn fluent_bundle(&self) -> Option<&Lrc<rustc_errors::FluentBundle>> {
-        None
-    }
-
-    fn fallback_fluent_bundle(&self) -> &rustc_errors::FluentBundle {
-        panic!("silent emitter attempted to translate a diagnostic");
-    }
-
-    // Override `translate_message` for the silent emitter because eager translation of
-    // subdiagnostics result in a call to this.
-    fn translate_message<'a>(
-        &'a self,
-        message: &'a rustc_errors::DiagnosticMessage,
-        _: &'a rustc_errors::translation::FluentArgs<'_>,
-    ) -> Result<Cow<'_, str>, rustc_errors::error::TranslateError<'_>> {
-        rustc_errors::emitter::silent_translate(message)
-    }
-}
-
-impl Emitter for SilentEmitter {
-    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
-        None
-    }
-
-    fn emit_diagnostic(&mut self, _diag: DiagInner) {}
-}
-
-fn silent_emitter() -> Box<DynEmitter> {
-    Box::new(SilentEmitter {})
-}
-
 /// Emit errors against every files expect ones specified in the `ignore_path_set`.
 struct SilentOnIgnoredFilesEmitter {
     ignore_path_set: IntoDynSyncSend<Lrc<IgnorePathSet>>,
@@ -143,17 +107,23 @@ fn default_dcx(
         ColorConfig::Never
     };
 
-    let emitter = if hide_parse_errors {
-        silent_emitter()
+    let fallback_bundle = rustc_errors::fallback_fluent_bundle(
+        rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec(),
+        false,
+    );
+    let emitter = Box::new(
+        HumanEmitter::new(stderr_destination(emit_color), fallback_bundle.clone())
+            .sm(Some(source_map.clone())),
+    );
+
+    let emitter: Box<DynEmitter> = if hide_parse_errors {
+        Box::new(SilentEmitter {
+            fallback_bundle,
+            fatal_dcx: DiagCtxt::new(emitter),
+            fatal_note: None,
+        })
     } else {
-        let fallback_bundle = rustc_errors::fallback_fluent_bundle(
-            rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec(),
-            false,
-        );
-        Box::new(
-            HumanEmitter::new(stderr_destination(emit_color), fallback_bundle)
-                .sm(Some(source_map.clone())),
-        )
+        emitter
     };
     DiagCtxt::new(Box::new(SilentOnIgnoredFilesEmitter {
         has_non_ignorable_parser_errors: false,
@@ -232,7 +202,14 @@ impl ParseSess {
     }
 
     pub(crate) fn set_silent_emitter(&mut self) {
-        self.parse_sess.dcx = DiagCtxt::new(silent_emitter());
+        // Ideally this invocation wouldn't be necessary and the fallback bundle in
+        // `self.parse_sess.dcx` could be used, but the lock in `DiagCtxt` prevents this.
+        // See `<rustc_errors::SilentEmitter as Translate>::fallback_fluent_bundle`.
+        let fallback_bundle = rustc_errors::fallback_fluent_bundle(
+            rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec(),
+            false,
+        );
+        self.parse_sess.dcx.make_silent(fallback_bundle, None);
     }
 
     pub(crate) fn span_to_filename(&self, span: Span) -> FileName {

src/tools/rustfmt/tests/source/issue-6082.rs

@@ -0,0 +1,5 @@
+macro_rules! test {
+    ($T:ident, $b:lifetime) => {
+        Box<$T<$b>>
+    };
+}

src/tools/rustfmt/tests/target/issue-6082.rs

@@ -0,0 +1,5 @@
+macro_rules! test {
+    ($T:ident, $b:lifetime) => {
+        Box<$T<$b>>
+    };
+}