From f2fd2d8c7080f7a7d770b3e3d27e525250c182dc Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sun, 31 Mar 2024 17:20:00 -0400
Subject: [PATCH] Make sure to insert Sized bound first into clauses list

---
 compiler/rustc_hir_analysis/src/bounds.rs     | 10 +++++--
 .../incremental/hashes/function_interfaces.rs |  2 +-
 ...verflow-due-to-sized-predicate-ordering.rs | 30 +++++++++++++++++++
 3 files changed, 39 insertions(+), 3 deletions(-)
 create mode 100644 tests/ui/methods/probe-overflow-due-to-sized-predicate-ordering.rs

diff --git a/compiler/rustc_hir_analysis/src/bounds.rs b/compiler/rustc_hir_analysis/src/bounds.rs
index d5465bb5dd5..d3f51195dfb 100644
--- a/compiler/rustc_hir_analysis/src/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/bounds.rs
@@ -54,14 +54,20 @@ fn push_trait_bound_inner(
         span: Span,
         polarity: ty::PredicatePolarity,
     ) {
-        self.clauses.push((
+        let clause = (
             trait_ref
                 .map_bound(|trait_ref| {
                     ty::ClauseKind::Trait(ty::TraitPredicate { trait_ref, polarity })
                 })
                 .to_predicate(tcx),
             span,
-        ));
+        );
+        // FIXME(-Znext-solver): We can likely remove this hack once the new trait solver lands.
+        if tcx.lang_items().sized_trait() == Some(trait_ref.def_id()) {
+            self.clauses.insert(0, clause);
+        } else {
+            self.clauses.push(clause);
+        }
     }
 
     pub fn push_projection_bound(
diff --git a/tests/incremental/hashes/function_interfaces.rs b/tests/incremental/hashes/function_interfaces.rs
index 3be30fab99c..4fa2762099c 100644
--- a/tests/incremental/hashes/function_interfaces.rs
+++ b/tests/incremental/hashes/function_interfaces.rs
@@ -217,7 +217,7 @@ pub fn second_trait_bound<T: Eq + Clone>() {}
 pub fn second_builtin_bound<T: Send        >() {}
 
 #[cfg(not(any(cfail1,cfail4)))]
-#[rustc_clean(cfg = "cfail2", except = "opt_hir_owner_nodes, predicates_of")]
+#[rustc_clean(cfg = "cfail2", except = "opt_hir_owner_nodes")]
 #[rustc_clean(cfg = "cfail3")]
 #[rustc_clean(cfg = "cfail5", except = "opt_hir_owner_nodes, predicates_of")]
 #[rustc_clean(cfg = "cfail6")]
diff --git a/tests/ui/methods/probe-overflow-due-to-sized-predicate-ordering.rs b/tests/ui/methods/probe-overflow-due-to-sized-predicate-ordering.rs
new file mode 100644
index 00000000000..08e15117c4b
--- /dev/null
+++ b/tests/ui/methods/probe-overflow-due-to-sized-predicate-ordering.rs
@@ -0,0 +1,30 @@
+//@ check-pass
+// Regression test due to #123279
+
+pub trait Job: AsJob {
+    fn run_once(&self);
+}
+
+impl<F: Fn()> Job for F {
+    fn run_once(&self) {
+        todo!()
+    }
+}
+
+pub trait AsJob {}
+
+// Ensure that `T: Sized + Job` by reordering the explicit `Sized` to where
+// the implicit sized pred would go.
+impl<T: Job + Sized> AsJob for T {}
+
+pub struct LoopingJobService {
+    job: Box<dyn Job>,
+}
+
+impl Job for LoopingJobService {
+    fn run_once(&self) {
+        self.job.run_once()
+    }
+}
+
+fn main() {}