Remove unstable flag

compiler/rustc_hir_typeck/src/lib.rs

@@ -153,6 +153,8 @@ fn diagnostic_only_typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::T
     typeck_with_fallback(tcx, def_id, fallback, None)
 }
 
+/// Same as `typeck` but `inspect` is invoked on evaluation of each root obligation.
+/// Inspecting obligations only works with the new trait solver.
 pub fn inspect_typeck<'tcx>(
     tcx: TyCtxt<'tcx>,
     def_id: LocalDefId,

compiler/rustc_infer/src/infer/mod.rs

@@ -1730,6 +1730,7 @@ impl<'tcx> InferCtxt<'tcx> {
         }
     }
 
+    /// Attach a callback to be invoked on each root obligation evaluated in the new trait solver.
     pub fn attach_obligation_inspector(&self, inspector: ObligationInspector<'tcx>) {
         debug_assert!(
             self.obligation_inspector.get().is_none(),

compiler/rustc_session/src/options.rs

@@ -1914,9 +1914,6 @@ written to standard error output)"),
         "for every macro invocation, print its name and arguments (default: no)"),
     track_diagnostics: bool = (false, parse_bool, [UNTRACKED],
         "tracks where in rustc a diagnostic was emitted"),
-    track_trait_obligations: bool = (false, parse_bool, [TRACKED],
-        "tracks evaluated obligations while trait solving, option is only \
-         valid when -Z next-solver=globally (default: no)"),
     // Diagnostics are considered side-effects of a query (see `QuerySideEffects`) and are saved
     // alongside query results and changes to translation options can affect diagnostics - so
     // translation options should be tracked.

compiler/rustc_trait_selection/src/solve/fulfill.rs

@@ -44,7 +44,7 @@ impl<'tcx> FulfillmentCtxt<'tcx> {
         FulfillmentCtxt { obligations: Vec::new(), usable_in_snapshot: infcx.num_open_snapshots() }
     }
 
-    fn track_evaluated_obligation(
+    fn inspect_evaluated_obligation(
         &self,
         infcx: &InferCtxt<'tcx>,
         obligation: &PredicateObligation<'tcx>,
@@ -119,7 +119,7 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentCtxt<'tcx> {
             for obligation in mem::take(&mut self.obligations) {
                 let goal = obligation.clone().into();
                 let result = infcx.evaluate_root_goal(goal, GenerateProofTree::IfEnabled).0;
-                self.track_evaluated_obligation(infcx, &obligation, &result);
+                self.inspect_evaluated_obligation(infcx, &obligation, &result);
                 let (changed, certainty, nested_goals) = match result {
                     Ok(result) => result,
                     Err(NoSolution) => {