trait system: comments and small nonfunctional changes

compiler/rustc_data_structures/src/obligation_forest/mod.rs

@@ -132,11 +132,11 @@ type ObligationTreeIdGenerator =
     std::iter::Map<std::ops::RangeFrom<usize>, fn(usize) -> ObligationTreeId>;
 
 pub struct ObligationForest<O: ForestObligation> {
-    /// The list of obligations. In between calls to `process_obligations`,
+    /// The list of obligations. In between calls to [Self::process_obligations],
     /// this list only contains nodes in the `Pending` or `Waiting` state.
     ///
     /// `usize` indices are used here and throughout this module, rather than
-    /// `rustc_index::newtype_index!` indices, because this code is hot enough
+    /// [`rustc_index::newtype_index!`] indices, because this code is hot enough
     /// that the `u32`-to-`usize` conversions that would be required are
     /// significant, and space considerations are not important.
     nodes: Vec<Node<O>>,
@@ -146,10 +146,11 @@ pub struct ObligationForest<O: ForestObligation> {
 
     /// A cache of the nodes in `nodes`, indexed by predicate. Unfortunately,
     /// its contents are not guaranteed to match those of `nodes`. See the
-    /// comments in `process_obligation` for details.
+    /// comments in [`Self::process_obligation` for details.
     active_cache: FxHashMap<O::CacheKey, usize>,
 
-    /// A vector reused in compress() and find_cycles_from_node(), to avoid allocating new vectors.
+    /// A vector reused in [Self::compress()] and [Self::find_cycles_from_node()],
+    /// to avoid allocating new vectors.
     reused_node_vec: Vec<usize>,
 
     obligation_tree_id_generator: ObligationTreeIdGenerator,

compiler/rustc_infer/src/infer/higher_ranked/mod.rs

@@ -123,7 +123,9 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         result
     }
 
-    /// See `infer::region_constraints::RegionConstraintCollector::leak_check`.
+    /// See [RegionConstraintCollector::leak_check][1].
+    ///
+    /// [1]: crate::infer::region_constraints::RegionConstraintCollector::leak_check
     pub fn leak_check(
         &self,
         overly_polymorphic: bool,

compiler/rustc_infer/src/infer/region_constraints/leak_check.rs

@@ -100,6 +100,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
 struct LeakCheck<'me, 'tcx> {
     tcx: TyCtxt<'tcx>,
     universe_at_start_of_snapshot: ty::UniverseIndex,
+    /// Only used when reporting region errors.
     overly_polymorphic: bool,
     mini_graph: &'me MiniGraph<'tcx>,
     rcc: &'me RegionConstraintCollector<'me, 'tcx>,

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -160,20 +160,12 @@ fn overlap<'cx, 'tcx>(
     );
 
     selcx.infcx().probe_maybe_skip_leak_check(skip_leak_check.is_yes(), |snapshot| {
-        overlap_within_probe(
-            selcx,
-            skip_leak_check,
-            impl1_def_id,
-            impl2_def_id,
-            overlap_mode,
-            snapshot,
-        )
+        overlap_within_probe(selcx, impl1_def_id, impl2_def_id, overlap_mode, snapshot)
     })
 }
 
 fn overlap_within_probe<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
-    skip_leak_check: SkipLeakCheck,
     impl1_def_id: DefId,
     impl2_def_id: DefId,
     overlap_mode: OverlapMode,
@@ -207,11 +199,11 @@ fn overlap_within_probe<'cx, 'tcx>(
         }
     }
 
-    if !skip_leak_check.is_yes() {
-        if infcx.leak_check(true, snapshot).is_err() {
-            debug!("overlap: leak check failed");
-            return None;
-        }
+    // We disable the leak when when creating the `snapshot` by using
+    // `infcx.probe_maybe_disable_leak_check`.
+    if infcx.leak_check(true, snapshot).is_err() {
+        debug!("overlap: leak check failed");
+        return None;
     }
 
     let intercrate_ambiguity_causes = selcx.take_intercrate_ambiguity_causes();

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -314,7 +314,7 @@ impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
             return ProcessResult::Unchanged;
         }
 
-        self.progress_changed_obligations(pending_obligation)
+        self.process_changed_obligations(pending_obligation)
     }
 
     fn process_backedge<'c, I>(
@@ -338,7 +338,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
     // actually uses this, so move this part of the code
     // out of that loop.
     #[inline(never)]
-    fn progress_changed_obligations(
+    fn process_changed_obligations(
         &mut self,
         pending_obligation: &mut PendingPredicateObligation<'tcx>,
     ) -> ProcessResult<PendingPredicateObligation<'tcx>, FulfillmentErrorCode<'tcx>> {

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -389,7 +389,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         for bound in matching_bounds {
             // FIXME(oli-obk): it is suspicious that we are dropping the constness and
             // polarity here.
-            let wc = self.evaluate_where_clause(stack, bound.map_bound(|t| t.trait_ref))?;
+            let wc = self.where_clause_may_apply(stack, bound.map_bound(|t| t.trait_ref))?;
             if wc.may_apply() {
                 candidates.vec.push(ParamCandidate(bound));
             }

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -1481,7 +1481,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .map_err(|_| ())
     }
 
-    fn evaluate_where_clause<'o>(
+    fn where_clause_may_apply<'o>(
         &mut self,
         stack: &TraitObligationStack<'o, 'tcx>,
         where_clause_trait_ref: ty::PolyTraitRef<'tcx>,