Remove quadratic behaviour from -Zunpretty=hir-tree.

Author: cjgillot

compiler/rustc_hir/src/hir.rs

@@ -796,7 +796,6 @@ impl<'tcx> AttributeMap<'tcx> {
 /// Map of all HIR nodes inside the current owner.
 /// These nodes are mapped by `ItemLocalId` alongside the index of their parent node.
 /// The HIR tree, including bodies, is pre-hashed.
-#[derive(Debug)]
 pub struct OwnerNodes<'tcx> {
     /// Pre-computed hash of the full HIR.
     pub hash_including_bodies: Fingerprint,
@@ -822,6 +821,18 @@ impl<'tcx> OwnerNodes<'tcx> {
     }
 }
 
+impl fmt::Debug for OwnerNodes<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("OwnerNodes")
+            .field("node", &self.nodes[ItemLocalId::from_u32(0)])
+            .field("bodies", &self.bodies)
+            .field("local_id_to_def_id", &self.local_id_to_def_id)
+            .field("hash_without_bodies", &self.hash_without_bodies)
+            .field("hash_including_bodies", &self.hash_including_bodies)
+            .finish()
+    }
+}
+
 /// Full information resulting from lowering an AST node.
 #[derive(Debug, HashStable_Generic)]
 pub struct OwnerInfo<'hir> {