errors: share SilentEmitter between rustc and rustfmt

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

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 `SubdiagMessage::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;