1 files changed, 53 insertions, 1 deletions

diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index cbfee582d..3064d2bed 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -408,6 +408,59 @@ impl EmissionGuarantee for ! {
     }
 }
 
+impl<'a> DiagnosticBuilder<'a, rustc_span::fatal_error::FatalError> {
+    /// Convenience function for internal use, clients should use one of the
+    /// `struct_*` methods on [`Handler`].
+    #[track_caller]
+    pub(crate) fn new_almost_fatal(
+        handler: &'a Handler,
+        message: impl Into<DiagnosticMessage>,
+    ) -> Self {
+        let diagnostic = Diagnostic::new_with_code(Level::Fatal, None, message);
+        Self::new_diagnostic_almost_fatal(handler, diagnostic)
+    }
+
+    /// Creates a new `DiagnosticBuilder` with an already constructed
+    /// diagnostic.
+    pub(crate) fn new_diagnostic_almost_fatal(
+        handler: &'a Handler,
+        diagnostic: Diagnostic,
+    ) -> Self {
+        debug!("Created new diagnostic");
+        Self {
+            inner: DiagnosticBuilderInner {
+                state: DiagnosticBuilderState::Emittable(handler),
+                diagnostic: Box::new(diagnostic),
+            },
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl EmissionGuarantee for rustc_span::fatal_error::FatalError {
+    fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
+        match db.inner.state {
+            // First `.emit()` call, the `&Handler` is still available.
+            DiagnosticBuilderState::Emittable(handler) => {
+                db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
+
+                handler.emit_diagnostic(&mut db.inner.diagnostic);
+            }
+            // `.emit()` was previously called, disallowed from repeating it.
+            DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
+        }
+        // Then fatally error..
+        rustc_span::fatal_error::FatalError
+    }
+
+    fn make_diagnostic_builder(
+        handler: &Handler,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> DiagnosticBuilder<'_, Self> {
+        DiagnosticBuilder::new_almost_fatal(handler, msg)
+    }
+}
+
 /// In general, the `DiagnosticBuilder` uses deref to allow access to
 /// the fields and methods of the embedded `diagnostic` in a
 /// transparent way. *However,* many of the methods are intended to
@@ -616,7 +669,6 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
         sp: impl Into<MultiSpan>,
         msg: impl Into<SubdiagnosticMessage>,
     ) -> &mut Self);
-    forward!(pub fn help_use_latest_edition(&mut self,) -> &mut Self);
     forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
 
     forward!(pub fn disable_suggestions(&mut self,) -> &mut Self);