Rollup merge of #98642 - yanchen4791:issue-98260-fix, r=spastorino

Fix #98260

Fixes https://github.com/rust-lang/rust/issues/98260

compiler/rustc_typeck/src/variance/mod.rs

@@ -37,6 +37,11 @@ fn crate_variances(tcx: TyCtxt<'_>, (): ()) -> CrateVariancesMap<'_> {
 }
 
 fn variances_of(tcx: TyCtxt<'_>, item_def_id: DefId) -> &[ty::Variance] {
+    // Skip items with no generics - there's nothing to infer in them.
+    if tcx.generics_of(item_def_id).count() == 0 {
+        return &[];
+    }
+
     match tcx.def_kind(item_def_id) {
         DefKind::Fn
         | DefKind::AssocFn