Make logging for drop-tracking easier to read.

Some of these are a little questionable because the output is so much longer, but I would really love to keep the bit that adds the pretty-printed expression to the generated CFG .dot file.

Before:
```
DEBUG rustc_typeck::check::generator_interior::drop_ranges::record_consumed_borrow consume PlaceWithHirId { hir_id: HirId { owner: DefId(0:7 ~ default_struct_update[79f9]::foo), local_id: 15 }, place: Place { base_ty: impl std::future::Future<Output = ()>, base: Rvalue, projections: [] } }; diag_expr_id=HirId { owner: DefId(0:7 ~ default_struct_update[79f9]::foo), local_id: 15 }, using parent expr HirId { owner: DefId(0:7 ~ default_struct_update[79f9]::foo), local_id: 49 }
```

After:
```
DEBUG rustc_typeck::check::generator_interior::drop_ranges::record_consumed_borrow consume PlaceWithHirId { hir_id: HirId { owner: DefId(0:7 ~ default_struct_update[79f9]::foo), local_id: 15 }, place: Place { base_ty: impl std::future::Future<Output = ()>, base: Rvalue, projections: [] } }; diag_expr_id=expr from_config(Config {
        nickname: None,
        ..Default::default()
    }) (hir_id=HirId { owner: DefId(0:7 ~ default_struct_update[79f9]::foo), local_id: 15 }), using parent expr
    .await (hir_id=HirId { owner: DefId(0:7 ~ default_struct_update[79f9]::foo), local_id: 49 })
```

Author: jyn514

compiler/rustc_typeck/src/check/generator_interior/drop_ranges.rs

@@ -109,7 +109,7 @@ rustc_index::newtype_index! {
 }
 
 /// Identifies a value whose drop state we need to track.
-#[derive(PartialEq, Eq, Hash, Debug, Clone, Copy)]
+#[derive(PartialEq, Eq, Hash, Clone, Copy)]
 enum TrackedValue {
     /// Represents a named variable, such as a let binding, parameter, or upvar.
     ///
@@ -121,6 +121,21 @@ enum TrackedValue {
     Temporary(HirId),
 }
 
+impl Debug for TrackedValue {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        ty::tls::with_opt(|opt_tcx| {
+            if let Some(tcx) = opt_tcx {
+                write!(f, "{}", tcx.hir().node_to_string(self.hir_id()))
+            } else {
+                match self {
+                    Self::Variable(hir_id) => write!(f, "Variable({:?})", hir_id),
+                    Self::Temporary(hir_id) => write!(f, "Temporary({:?})", hir_id),
+                }
+            }
+        })
+    }
+}
+
 impl TrackedValue {
     fn hir_id(&self) -> HirId {
         match self {
@@ -148,7 +163,7 @@ enum TrackedValueConversionError {
     /// Place projects are not currently supported.
     ///
     /// The reasoning around these is kind of subtle, so we choose to be more
-    /// conservative around these for now. There is not reason in theory we
+    /// conservative around these for now. There is no reason in theory we
     /// cannot support these, we just have not implemented it yet.
     PlaceProjectionsNotSupported,
 }

compiler/rustc_typeck/src/check/generator_interior/drop_ranges/cfg_build.rs

@@ -129,13 +129,14 @@ impl<'a, 'tcx> DropRangeVisitor<'a, 'tcx> {
     /// ExprUseVisitor's consume callback doesn't go deep enough for our purposes in all
     /// expressions. This method consumes a little deeper into the expression when needed.
     fn consume_expr(&mut self, expr: &hir::Expr<'_>) {
-        debug!("consuming expr {:?}, count={:?}", expr.hir_id, self.expr_index);
+        debug!("consuming expr {:?}, count={:?}", expr.kind, self.expr_index);
         let places = self
             .places
             .consumed
             .get(&expr.hir_id)
             .map_or(vec![], |places| places.iter().cloned().collect());
         for place in places {
+            trace!(?place, "consuming place");
             for_each_consumable(self.hir, place, |value| self.record_drop(value));
         }
     }

compiler/rustc_typeck/src/check/generator_interior/drop_ranges/cfg_visualize.rs

@@ -74,12 +74,18 @@ impl<'a> dot::Labeller<'a> for DropRangesGraph<'_, '_> {
 
     fn node_label(&'a self, n: &Self::Node) -> dot::LabelText<'a> {
         dot::LabelText::LabelStr(
-            self.drop_ranges
-                .post_order_map
-                .iter()
-                .find(|(_hir_id, &post_order_id)| post_order_id == *n)
-                .map_or("<unknown>".into(), |(hir_id, _)| self.tcx.hir().node_to_string(*hir_id))
-                .into(),
+            format!(
+                "{n:?}: {}",
+                self.drop_ranges
+                    .post_order_map
+                    .iter()
+                    .find(|(_hir_id, &post_order_id)| post_order_id == *n)
+                    .map_or("<unknown>".into(), |(hir_id, _)| self
+                        .tcx
+                        .hir()
+                        .node_to_string(*hir_id))
+            )
+            .into(),
         )
     }
 }

compiler/rustc_typeck/src/check/generator_interior/drop_ranges/record_consumed_borrow.rs

@@ -75,6 +75,7 @@ impl<'tcx> ExprUseDelegate<'tcx> {
         if !self.places.consumed.contains_key(&consumer) {
             self.places.consumed.insert(consumer, <_>::default());
         }
+        debug!(?consumer, ?target, "mark_consumed");
         self.places.consumed.get_mut(&consumer).map(|places| places.insert(target));
     }
 
@@ -136,13 +137,16 @@ impl<'tcx> expr_use_visitor::Delegate<'tcx> for ExprUseDelegate<'tcx> {
         place_with_id: &expr_use_visitor::PlaceWithHirId<'tcx>,
         diag_expr_id: HirId,
     ) {
-        let parent = match self.tcx.hir().find_parent_node(place_with_id.hir_id) {
+        let hir = self.tcx.hir();
+        let parent = match hir.find_parent_node(place_with_id.hir_id) {
             Some(parent) => parent,
             None => place_with_id.hir_id,
         };
         debug!(
-            "consume {:?}; diag_expr_id={:?}, using parent {:?}",
-            place_with_id, diag_expr_id, parent
+            "consume {:?}; diag_expr_id={}, using parent {}",
+            place_with_id,
+            hir.node_to_string(diag_expr_id),
+            hir.node_to_string(parent)
         );
         place_with_id
             .try_into()