Slightly refactor the dumping of HIR analysis data

compiler/rustc_hir_analysis/src/variance/dump.rs

@@ -0,0 +1,32 @@
+use rustc_hir::def::DefKind;
+use rustc_hir::def_id::CRATE_DEF_ID;
+use rustc_middle::ty::TyCtxt;
+use rustc_span::symbol::sym;
+
+pub(crate) fn variances(tcx: TyCtxt<'_>) {
+    if tcx.has_attr(CRATE_DEF_ID, sym::rustc_variance_of_opaques) {
+        for id in tcx.hir().items() {
+            let DefKind::OpaqueTy = tcx.def_kind(id.owner_id) else { continue };
+
+            let variances = tcx.variances_of(id.owner_id);
+
+            tcx.dcx().emit_err(crate::errors::VariancesOf {
+                span: tcx.def_span(id.owner_id),
+                variances: format!("{variances:?}"),
+            });
+        }
+    }
+
+    for id in tcx.hir().items() {
+        if !tcx.has_attr(id.owner_id, sym::rustc_variance) {
+            continue;
+        }
+
+        let variances = tcx.variances_of(id.owner_id);
+
+        tcx.dcx().emit_err(crate::errors::VariancesOf {
+            span: tcx.def_span(id.owner_id),
+            variances: format!("{variances:?}"),
+        });
+    }
+}