Make E0599 a structured error

compiler/rustc_hir_analysis/src/errors.rs

@@ -1417,6 +1417,15 @@ pub(crate) struct CrossCrateTraitsDefined {
     pub traits: String,
 }
 
+#[derive(Diagnostic)]
+#[diag(hir_analysis_no_variant_named, code = E0599)]
+pub struct NoVariantNamed<'tcx> {
+    #[primary_span]
+    pub span: Span,
+    pub ident: Ident,
+    pub ty: Ty<'tcx>,
+}
+
 // FIXME(fmease): Deduplicate:
 
 #[derive(Diagnostic)]