diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index f598fa088428..31892790cb44 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -509,11 +509,11 @@ pub enum StashKey {
     Cycle,
 }
 
-fn default_track_diagnostic(d: &mut Diagnostic, f: &mut dyn FnMut(&mut Diagnostic)) {
-    (*f)(d)
+fn default_track_diagnostic(diag: Diagnostic, f: &mut dyn FnMut(Diagnostic)) {
+    (*f)(diag)
 }
 
-pub static TRACK_DIAGNOSTICS: AtomicRef<fn(&mut Diagnostic, &mut dyn FnMut(&mut Diagnostic))> =
+pub static TRACK_DIAGNOSTICS: AtomicRef<fn(Diagnostic, &mut dyn FnMut(Diagnostic))> =
     AtomicRef::new(&(default_track_diagnostic as _));
 
 #[derive(Copy, Clone, Default)]
@@ -1079,17 +1079,8 @@ impl DiagCtxt {
         self.inner.borrow_mut().emitter.emit_diagnostic(&db);
     }
 
-    pub fn emit_diagnostic(&self, mut diagnostic: Diagnostic) -> Option<ErrorGuaranteed> {
-        self.emit_diagnostic_without_consuming(&mut diagnostic)
-    }
-
-    // It's unfortunate this exists. `emit_diagnostic` is preferred, because it
-    // consumes the diagnostic, thus ensuring it is emitted just once.
-    pub(crate) fn emit_diagnostic_without_consuming(
-        &self,
-        diagnostic: &mut Diagnostic,
-    ) -> Option<ErrorGuaranteed> {
-        self.inner.borrow_mut().emit_diagnostic_without_consuming(diagnostic)
+    pub fn emit_diagnostic(&self, diagnostic: Diagnostic) -> Option<ErrorGuaranteed> {
+        self.inner.borrow_mut().emit_diagnostic(diagnostic)
     }
 
     #[track_caller]
@@ -1278,13 +1269,6 @@ impl DiagCtxtInner {
     }
 
     fn emit_diagnostic(&mut self, mut diagnostic: Diagnostic) -> Option<ErrorGuaranteed> {
-        self.emit_diagnostic_without_consuming(&mut diagnostic)
-    }
-
-    fn emit_diagnostic_without_consuming(
-        &mut self,
-        diagnostic: &mut Diagnostic,
-    ) -> Option<ErrorGuaranteed> {
         if matches!(diagnostic.level, Error | Fatal) && self.treat_err_as_bug() {
             diagnostic.level = Bug;
         }
@@ -1340,7 +1324,7 @@ impl DiagCtxtInner {
         }
 
         let mut guaranteed = None;
-        (*TRACK_DIAGNOSTICS)(diagnostic, &mut |diagnostic| {
+        (*TRACK_DIAGNOSTICS)(diagnostic, &mut |mut diagnostic| {
             if let Some(ref code) = diagnostic.code {
                 self.emitted_diagnostic_codes.insert(code.clone());
             }
@@ -1376,7 +1360,7 @@ impl DiagCtxtInner {
                     );
                 }
 
-                self.emitter.emit_diagnostic(diagnostic);
+                self.emitter.emit_diagnostic(&diagnostic);
                 if diagnostic.is_error() {
                     self.deduplicated_err_count += 1;
                 } else if let Warning(_) = diagnostic.level {
diff --git a/compiler/rustc_interface/src/callbacks.rs b/compiler/rustc_interface/src/callbacks.rs
index ef00ced67ffe..7458be2c86da 100644
--- a/compiler/rustc_interface/src/callbacks.rs
+++ b/compiler/rustc_interface/src/callbacks.rs
@@ -29,7 +29,7 @@ fn track_span_parent(def_id: rustc_span::def_id::LocalDefId) {
 /// This is a callback from `rustc_errors` as it cannot access the implicit state
 /// in `rustc_middle` otherwise. It is used when diagnostic messages are
 /// emitted and stores them in the current query, if there is one.
-fn track_diagnostic(diagnostic: &mut Diagnostic, f: &mut dyn FnMut(&mut Diagnostic)) {
+fn track_diagnostic(diagnostic: Diagnostic, f: &mut dyn FnMut(Diagnostic)) {
     tls::with_context_opt(|icx| {
         if let Some(icx) = icx {
             if let Some(diagnostics) = icx.diagnostics {