From 63522835f768862163248ea9942ccb959eadf318 Mon Sep 17 00:00:00 2001
From: gavinleroy <gavinleroy6@gmail.com>
Date: Thu, 18 Jan 2024 11:24:28 +0100
Subject: [PATCH] Remove unstable flag

---
 compiler/rustc_hir_typeck/src/lib.rs          |  2 ++
 compiler/rustc_infer/src/infer/mod.rs         |  1 +
 compiler/rustc_session/src/options.rs         |  3 --
 .../src/solve/fulfill.rs                      |  4 +--
 tests/ui/traits/track_trait_obligations.rs    | 32 -------------------
 5 files changed, 5 insertions(+), 37 deletions(-)
 delete mode 100644 tests/ui/traits/track_trait_obligations.rs

diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index 81f5e505f76c3..f7d198c8bd47f 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/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,
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index f5d03ad1cccc3..39c41a93c3bd1 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/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(),
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index f14e288beb6b4..f4bf79f93f287 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/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.
diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index df4f14350fb62..ee07f453b9549 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/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) => {
diff --git a/tests/ui/traits/track_trait_obligations.rs b/tests/ui/traits/track_trait_obligations.rs
deleted file mode 100644
index 92add912fe0c2..0000000000000
--- a/tests/ui/traits/track_trait_obligations.rs
+++ /dev/null
@@ -1,32 +0,0 @@
-// compile-flags: -Ztrack-trait-obligations
-// run-pass
-
-// Just making sure this flag is accepted and doesn't crash the compiler
-use traits::IntoString;
-
-fn does_impl_into_string<T: IntoString>(_: T) {}
-
-fn main() {
-    let v = vec![(0, 1), (2, 3)];
-
-    does_impl_into_string(v);
-}
-
-mod traits {
-    pub trait IntoString {
-        fn to_string(&self) -> String;
-    }
-
-    impl IntoString for (i32, i32) {
-        fn to_string(&self) -> String {
-            format!("({}, {})", self.0, self.1)
-        }
-    }
-
-    impl<T: IntoString> IntoString for Vec<T> {
-        fn to_string(&self) -> String {
-            let s = self.iter().map(|v| v.to_string()).collect::<Vec<_>>().join(", ");
-            format!("[{s}]")
-        }
-    }
-}