1 files changed, 8 insertions, 0 deletions
diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index 728d890ca60..19e9e33ab80 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -103,3 +103,11 @@ pub(crate) struct UnallowedFnPointerCall {
     pub span: Span,
     pub kind: ConstContext,
 }
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::unstable_const_fn)]
+pub(crate) struct UnstableConstFn {
+    #[primary_span]
+    pub span: Span,
+    pub def_id: String,
+}