Rollup merge of #108460 - obeis:hir-analysis-migrate-diagnostics-2, r=compiler-errors

migrate `rustc_hir_analysis` to session diagnostic [Part Two]

migrate `rustc_hir_analysis` to session diagnostic (part two)
files list:
- rustc_hir_analysis/variance/*
- rustc_hir_analysis/missing_cast_for_variadic_arg.rs
- rustc_hir_analysis/sized_unsized_cast.rs

Updates #100717

compiler/rustc_hir_analysis/src/variance/test.rs

@@ -1,6 +1,8 @@
 use rustc_middle::ty::TyCtxt;
 use rustc_span::symbol::sym;
 
+use crate::errors;
+
 pub fn test_variance(tcx: TyCtxt<'_>) {
     // For unit testing: check for a special "rustc_variance"
     // attribute and report an error with various results if found.
@@ -8,7 +10,10 @@ pub fn test_variance(tcx: TyCtxt<'_>) {
         if tcx.has_attr(id.owner_id.to_def_id(), sym::rustc_variance) {
             let variances_of = tcx.variances_of(id.owner_id);
 
-            tcx.sess.struct_span_err(tcx.def_span(id.owner_id), format!("{variances_of:?}")).emit();
+            tcx.sess.emit_err(errors::VariancesOf {
+                span: tcx.def_span(id.owner_id),
+                variances_of: format!("{variances_of:?}"),
+            });
         }
     }
 }