Add proper cfgs for struct HirIdValidator used only with debug assert…

…ions

compiler/rustc_passes/src/hir_id_validator.rs

@@ -1,8 +1,8 @@
 use rustc_data_structures::sync::Lock;
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
-use rustc_hir::intravisit;
-use rustc_hir::{HirId, ItemLocalId};
+#[cfg(debug_assertions)]
+use rustc_hir::{intravisit, HirId, ItemLocalId};
 use rustc_index::bit_set::GrowableBitSet;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::TyCtxt;
@@ -36,13 +36,15 @@ pub fn check_crate(tcx: TyCtxt<'_>) {
     }
 }
 
+#[cfg(debug_assertions)]
 struct HirIdValidator<'a, 'hir> {
     tcx: TyCtxt<'hir>,
     owner: Option<hir::OwnerId>,
     hir_ids_seen: GrowableBitSet<ItemLocalId>,
     errors: &'a Lock<Vec<String>>,
 }
 
+#[cfg(debug_assertions)]
 impl<'a, 'hir> HirIdValidator<'a, 'hir> {
     fn new_visitor(&self, tcx: TyCtxt<'hir>) -> HirIdValidator<'a, 'hir> {
         HirIdValidator { tcx, owner: None, hir_ids_seen: Default::default(), errors: self.errors }
@@ -114,6 +116,7 @@ impl<'a, 'hir> HirIdValidator<'a, 'hir> {
     }
 }
 
+#[cfg(debug_assertions)]
 impl<'a, 'hir> intravisit::Visitor<'hir> for HirIdValidator<'a, 'hir> {
     type NestedFilter = nested_filter::OnlyBodies;